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使用servlet+jsp实现学生管理系统_jsp+servlet+spring+dao系统

作者：运维做开发 | 2024-06-21 08:22:49

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jsp+servlet+spring+dao系统

使用Servlet+JSP实现学生管理系统

eg1: 使用servlet来实现登录功能

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>登录页面</h1>
<!--前端访问后台资源 不加/-->
<form action="login" method="post">

    用户名: <input type="text" name="username"><br/>
    密码： <input type="password" name="password"><br/>
    爱好： <input type="checkbox" name="love" value="1">学习
    <input type="checkbox" name="love" value="2">篮球
    <input type="checkbox" name="love" value="3">游戏<br/>
    <input type="submit" value="登录">
</form>
</body>
</html>

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LoginServlet:

package com.jishou.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("post请求。。。。。");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("get请求。。。。");
    }
}

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登录逻辑里面取前台用户输入的参数：

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //登录的处理逻辑
        //1. 取前台表单的参数  request
        /*
        	public String getParameter(String name)					  返回指定name对应的参数的值

	public String[] getParameterValues(String name)		返回指定name对应的一组参数值，返回值是数组

	public Enumeration getParameterNames()  				 返回所有客户请求的参数名
         */

        //2. 登录处理
        //参数名必须和前台表单name属性值一致
        request.setCharacterEncoding("utf-8");//设置请求编码 放在第一行
        String username = request.getParameter("username");//取用户名
        String password = request.getParameter("password");//取密码
        String[] loves = request.getParameterValues("love");//取爱好

        System.out.println("用户名： "+username+" 密码："+password);
        if(loves!=null&&loves.length>0){
            for(String love: loves){
                System.out.println("爱好： "+love);
            }
        }

        //3. 产生响应 成功或者失败
        //通过response响应对象输出内容到浏览器里面
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html");//说明以html方式来响应
        PrintWriter out = response.getWriter();//获取字符输出流
        out.println("用户名是："+username+"密码是： "+password);
        out.flush();//刷新流
        out.close();//关闭流
    }
}
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url访问：

http://localhost:8080/servlet02_2_war_exploded/login.html
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eg2: 使用servlet来实现登录功能

1.创建数据库表 mysql

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-B1XWDjyA-1638964004199)(img\user.png)]

2.创建web project

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-bcr8v8cE-1638964004202)(img\stuManage.png)]

3. 在web目录下创建登录页面 login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>登录页面</h1>
<!--前端访问后台资源 不加/-->
<form action="login" method="post">

    用户名: <input type="text" name="username"><br/>
    密码： <input type="password" name="password"><br/>

    <input type="submit" value="登录">
</form>
</body>
</html>



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4.编写实体类User

package com.jishou.pojo;

public class User {

    private int id;
    private String username;
    private String password;

    public User() {
    }

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

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5.编写数据访问层 UserDao接口和接口实现类

导入mysql依赖，复制到web–web-inf下的lib目录底下：

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注意： web项目中mysql依赖包必须复制到web-inf下面的lib目录里面

吧mysql依赖引入到该工程里面

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-Z7smX22l-1638964004205)(img\yilai1.png)]

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-s4Sqo6zS-1638964004207)(img\yilai2.png)]

数据库连接工具类 DBUtil

package com.jishou.util;

import java.sql.*;


public class DBUtil {

    private  static String driverClassName="com.mysql.jdbc.Driver";
    private  static String url="jdbc:mysql://localhost:3306/test?characterEncoding=utf8";
    private  static String username="root";
    private  static String password="123456";

    static{

        try {
            Class.forName(driverClassName);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection(){
        try {
            return DriverManager.getConnection(url, username, password);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return  null;
    }

    public static void close(Connection conn, PreparedStatement pstmt, ResultSet rs){
       try {
           if (rs != null) {
               rs.close();
           }
           if (pstmt != null) {
               pstmt.close();
           }
           if (conn != null) {
               conn.close();

           }
       }catch (SQLException e){
           e.printStackTrace();
       }
    }

    public static void close(Connection conn, PreparedStatement pstmt){
        try {

            if (pstmt != null) {
                pstmt.close();
            }
            if (conn != null) {
                conn.close();

            }
        }catch (SQLException e){
            e.printStackTrace();
        }
    }
}

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UserDao

package com.jishou.dao;

import com.jishou.pojo.User;

public interface UserDao {

    public User queryOneUser(User user) ;

    public int insertUser(User user);
}

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UserDaoImpl

package com.jishou.dao;

import com.jishou.pojo.User;
import com.jishou.util.DBUtil;

import java.sql.*;

public class UserDaoImpl implements UserDao{

    /*@Override
    public User queryOneUser(User user) throws SQLException, ClassNotFoundException {
        //1.加载驱动      建厂
        String driverClassName="com.mysql.jdbc.Driver";
        String url="jdbc://mysql:localhost:3306/test?characterEncoding=utf8";
        String username="root";
        String password="123456";

        String sql="select * from user where username=? and password=?";

        User u=null;

        Class.forName(driverClassName);
        //2.获取连接      修路
        Connection conn = DriverManager.getConnection(url, username, password);
        //3.创建PreparedStatement    造车
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setString(1,user.getUsername());
        pstmt.setString(2,user.getPassword());
        //4.执行操作    拉货
        ResultSet rs = pstmt.executeQuery();
        //5.处理结果集  查询会有结果集 增删改 没有    处理货物
        if(rs.next()){
            int id = rs.getInt(1);
            String name = rs.getString(2);
            String pass = rs.getString(3);

            u=new User(id,name,pass);
        }
        //6. 关闭资源    路 砸了   货物 毁了 车 砸了
        if(rs!=null){
            rs.close();
        }
        if(pstmt!=null){
            pstmt.close();
        }
        if(conn!=null){
            conn.close();

        }
        return u;
    }*/

    public User queryOneUser(User user)  {
        //1.加载驱动      建厂
        String sql="select * from user where username=? and password=?";

        User u=null;
        Connection conn=null;
        PreparedStatement pstmt=null;
        ResultSet rs=null;

        try {
            //2.获取连接      修路

            conn= DBUtil.getConnection();
            //3.创建PreparedStatement    造车
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUsername());
            pstmt.setString(2, user.getPassword());
            //4.执行操作    拉货
            rs = pstmt.executeQuery();
            //5.处理结果集  查询会有结果集 增删改 没有    处理货物
            if (rs.next()) {
                int id = rs.getInt(1);
                String name = rs.getString(2);
                String pass = rs.getString(3);

                u = new User(id, name, pass);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }
        //6. 关闭资源    路 砸了   货物 毁了 车 砸了
        DBUtil.close(conn,pstmt,rs);
        return u;
    }

    @Override
    public int insertUser(User user) {
        return 0;
    }
}

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6.编写service层接口和实现类

UserService

package com.jishou.service;

import com.jishou.pojo.User;

public interface UserService {

    //登录
    public User login(User user);
    //注册
    public boolean register(User user);
}

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UserServiceImpl

package com.jishou.service;

import com.jishou.dao.UserDao;
import com.jishou.dao.UserDaoImpl;
import com.jishou.pojo.User;

public class UserServiceImpl  implements UserService{

    private  UserDao userDao=new UserDaoImpl();

    @Override
    public User login(User user) {
        return userDao.queryOneUser(user);
    }

    @Override
    public boolean register(User user) {
        return false;
    }
}

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7.编写Servlet的登录实现逻辑

LoginServlet

package com.jishou.servlet;

import com.jishou.pojo.User;
import com.jishou.service.UserService;
import com.jishou.service.UserServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    private UserService userService=new UserServiceImpl();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 取参数
        request.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        User qtUser=new User(username,password);
        //连数据库查询
        User htUser = userService.login(qtUser);
        //响应
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        //判断是否登录成功
        if(htUser!=null){
            out.println("<h1>登录成功</h1>");
        }else{
            out.println("<h1>登录失败</h1>");
        }
        out.flush();
        out.close();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

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8.浏览器url访问登录页面，展示运行效果

http://localhost:8080/stuManage_02_war_exploded/login.html
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正常jdbc流程：

 public User queryOneUser(User user) throws SQLException, ClassNotFoundException {
        //1.加载驱动      建厂
        String driverClassName="com.mysql.jdbc.Driver";
        String url="jdbc://mysql:localhost:3306/test?characterEncoding=utf8";
        String username="root";
        String password="123456";

        String sql="select * from user where username=? and password=?";

        User u=null;

        Class.forName(driverClassName);
        //2.获取连接      修路
        Connection conn = DriverManager.getConnection(url, username, password);
        //3.创建PreparedStatement    造车
        PreparedStatement pstmt = conn.prepareStatement(sql);
        pstmt.setString(1,user.getUsername());
        pstmt.setString(2,user.getPassword());
        //4.执行操作    拉货
        ResultSet rs = pstmt.executeQuery();
        //5.处理结果集  查询会有结果集 增删改 没有    处理货物
        if(rs.next()){
            int id = rs.getInt(1);
            String name = rs.getString(2);
            String pass = rs.getString(3);

            u=new User(id,name,pass);
        }
        //6. 关闭资源    路 砸了   货物 毁了 车 砸了
         if(rs!=null){
            rs.close();
        }
        if(pstmt!=null){
            pstmt.close();
        }
        if(conn!=null){
            conn.close();
           
        }
        return u;
    }
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eg3: 使用Servlet实现注册功能

在web目录下新建register.html文件

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<h1>注册页面</h1>

<!--前端访问路径都不加/ -->
<form action="register" method="post">
    用户名： <input type="text" name="username"><br>
    密码： <input type="password" name="password"><br>
    <input type="submit" value="注册">
</form>
</body>
</html>

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编写数据访问层UserDao和实现类里面的注册逻辑

UserDao接口

 public int insertUser(User user);
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UserDaoImpl接口实现类

  @Override
    public int insertUser(User user) {

        String sql="INSERT INTO user (username, password) VALUES ( ?, ?)";
        Connection conn = DBUtil.getConnection();
        PreparedStatement pstmt=null;
        int row=0;
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getUsername());
            pstmt.setString(2, user.getPassword());
            row = pstmt.executeUpdate();
        }catch(SQLException e) {
            e.printStackTrace();
        }finally {
            DBUtil.close(pstmt,conn);
        }
        return row;
    }
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编写service层注册逻辑

UserService接口：

  public boolean register(User user);//注册
  
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UserServiceImpl接口实现类

 @Override
    public boolean register(User user) {
        int row = userDao.insertUser(user);
        if(row>0){
            return true;
        }
        return false;
    }
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编写RegisterServlet注册实现逻辑

RegisterServlet

package com.jishou.servlet;

import com.jishou.pojo.User;
import com.jishou.service.UserService;
import com.jishou.service.UserServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "RegisterServlet",urlPatterns = "/register")
public class RegisterServlet extends HttpServlet {

    private UserService userService=new UserServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //取参
        req.setCharacterEncoding("utf-8");
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        User qtUser=new User(username,password);

        //链接数据库添加
        boolean flag = userService.register(qtUser);

        /*resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html");
        PrintWriter out = resp.getWriter();

        //响应
        if(flag){
            out.println("<h1>注册成功<h1>");
        }else {
            out.println("<h1>注册失败<h1>");
        }
        out.flush();
        out.close();*/

        //注册成功 需要跳转到登录页面，注册失败 需要 回到注册页面，继续注册
        if(flag){
            //重定向 就表示重新定位到一个地址
            resp.sendRedirect("login.html");
        }else{
            resp.sendRedirect("register.html");
        }


    }
}


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浏览器url访问测试,展示运行效果

http://localhost:8080/stuManage_04_war_exploded/register.html
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eg4: 使用Servlet实现查询所有学生信息功能

创建数据库表

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-cVN6h43P-1638964004208)(img\stu.png)]

编写实体类

Student

package com.jishou.pojo;

import java.util.Date;

public class Student {
    private Integer id;
    private String name;
    private Date birthday;
    private Integer age;
    private String address;
    private String photo;

    public Student() {
    }

    public Student(Integer id, String name, Date birthday, Integer age, String address, String photo) {
        this.id = id;
        this.name = name;
        this.birthday = birthday;
        this.age = age;
        this.address = address;
        this.photo = photo;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getPhoto() {
        return photo;
    }

    public void setPhoto(String photo) {
        this.photo = photo;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", birthday=" + birthday +
                ", age=" + age +
                ", address='" + address + '\'' +
                ", photo='" + photo + '\'' +
                '}';
    }
}
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数据访问层StudentDao,StudentDaoImpl查询所有

StudentDao

package com.jishou.dao;

import com.jishou.pojo.Student;

import java.util.List;

public interface StudentDao {

    public List<Student> queryAllStudents();
}
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StudentDaoImpl

package com.jishou.dao;

import com.jishou.pojo.Student;
import com.jishou.util.DBUtil;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDaoImpl implements StudentDao{
    @Override
    public List<Student> queryAllStudents() {

        String sql="select * from stu";

        PreparedStatement pstmt=null;
        ResultSet rs=null;
        List<Student> list=new ArrayList<>();

        //2. 获取连接   修路
        Connection conn = DBUtil.getConnection();
        try {
            //3. 创建PreparedStatement   造车
            pstmt = conn.prepareStatement(sql);

            //4. 执行sql    拉货
            rs = pstmt.executeQuery();
            //5. 处理结果集 查询会有结果集  处理货物
            while (rs.next()) {
                int id = rs.getInt(1);
                String name = rs.getString(2);
                Date birthday = rs.getDate(3);
                int age = rs.getInt(4);
                String address = rs.getString(5);
                String photo = rs.getString(6);
                Student student=new Student(id,name,birthday,age,address,photo);
                list.add(student);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            //6. 关闭资源   货 车 路全都毁了
            DBUtil.close(rs,pstmt,conn);
        }

        return list;
    }
}
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服务层service层接口和实现

StudentService

package com.jishou.service;

import com.jishou.pojo.Student;

import java.util.List;

public interface StudentService {
    public List<Student> queryAllStudents();
}
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StudentServiceImpl

package com.jishou.service;

import com.jishou.dao.StudentDao;
import com.jishou.dao.StudentDaoImpl;
import com.jishou.pojo.Student;

import java.util.List;

public class StudentServiceImpl implements StudentService{

    private StudentDao studentDao=new StudentDaoImpl();

    @Override
    public List<Student> queryAllStudents() {
        return studentDao.queryAllStudents();
    }
}
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查询所有的Servlet实现

ListServlet

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.ServerSocket;
import java.util.List;

@WebServlet(name = "ListServlet",urlPatterns = "/list")
public class ListServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //查询所有学生
        List<Student> list = studentService.queryAllStudents();
        //吧学生信息放在request对象里面
        req.setAttribute("list",list);
        //请求转发
        req.getRequestDispatcher("list.jsp").forward(req,resp);
    }
}
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前端页面

list.jsp

<%@ page import="com.jishou.pojo.Student" %>
<%@ page import="java.util.List" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<h1>学生管理系统</h1>
<table>
    <tr>
        <td>编号</td>
        <td>姓名</td>
        <td>出生日期</td>
        <td>年龄</td>
        <td>地址</td>
        <td><a href="">添加学生</a></td>
    </tr>


    <c:forEach var="s" items="${requestScope.list}">
        <tr>
            <td>${s.id}</td>
            <td>${s.name}</td>
            <td>${s.birthday}</td>
            <td>${s.age}</td>
            <td>${s.address}</td>
            <td>
                <a href="">修改</a>
                <a href="">删除</a>
            </td>
        </tr>
    </c:forEach>
</table>

</body>
</html>
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浏览器url访问

http://localhost:8080/stuManage_04_war_exploded/list

eg5: 实现在首页展示当前用户名功能，退出系统功能，展示当前服务器总在线人数功能

LoginServlet：

package com.jishou.servlet;

import com.jishou.pojo.User;
import com.jishou.service.UserService;
import com.jishou.service.UserServiceImpl;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    private UserService userService=new UserServiceImpl();

    private Integer count=0;//总在线人数

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 取前台参数
        request.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        User qtuser=new User(username,password);
        //2. 连接数据库查询
        User htuser = userService.login(qtuser);
        //3. 判断登录是否成功
       
        if(htuser!=null){
            //登录成功
			HttpSession session = request.getSession();
        	ServletContext servletContext = request.getServletContext();
            session.setAttribute("user",htuser);
            servletContext.setAttribute("count",++count);
            response.sendRedirect("list");
        }else{
            //登录失败
            response.sendRedirect("login.html");
        }
    }
}
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LogOutServlet：

package com.jishou.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet(name = "LogOutServlet",urlPatterns = "/logout")
public class LogOutServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        HttpSession session = req.getSession();
        session.invalidate();//session失效
        //让总在线人数减少
        ServletContext servletContext = req.getServletContext();
        Integer count = (Integer) servletContext.getAttribute("count");
        servletContext.setAttribute("count",--count);
        resp.sendRedirect("login.html");
    }
}
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list.jsp

加上下面代码：

<%
    List<Student> list = (List<Student>) request.getAttribute("list");
    User user = (User) request.getSession().getAttribute("user");
%>
<div id="login">欢迎<%=user.getUsername()%>登录 <a href="logout">退出系统</a></div>
<div id="count">当前共有<%=application.getAttribute("count")%>人在线</div>
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eg6: 使用Servlet实现添加、删除和修改学生信息功能

思路：

添加：

<a href="add.jsp">添加学生</a>
当在主页面点击添加超链接时--->跳转到add.jsp----->add.jsp表单里面输入相应值时，跳转AddServlet,实现添加逻辑
----->AddServlet实现添加功能------>添加成功，跳转到ListServlet，添加失败，回到添加页面add.jsp
注意： 数据库表主键id自增，所以不用添加id属性
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删除：

<a href="delete?id=<%=s.getId()%>">删除</a>
删除要根据id来删除该条数据信息；当点击删除超链接时，需要跳转到DeleteServlet，并吧要删除的id传过去,删除成功，再重新查询所有
超链接访问属于get请求方式，get请求走浏览器地址栏传参，所以href="delete?id=<%=s.getId()%>" 即可
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修改：

修改的实现逻辑是在update.jsp里面在原来老数据的基础之上吧老数据修改成新数据，所以，修改的逻辑需要先根据id来查询单个，查询出来的对象信息回显到update.jsp表单里面，用户再在老数据的基础之上输入新数据，点击修改按钮，实现后台的修改功能；修改成功，回到主页面，查询所有；修改失败，回到update.jsp


list.jsp  <a href="load?id=<%=s.getId()%>">修改</a>  ----->LoadServlet 根据id查询单个---->
update.jsp 实现老数据回显------>用户在老数据的基础之上吧老数据修改成新数据，submit修改按钮----->
UpdateServlet 修改的后台实现----->修改成功，ListServlet；修改失败，回到update.jsp
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注意： 由于数据库中birthday是date类型，他对应的java代码中的类型为java.sql.Date; 而平时java代码使用最多的是java.util.Date.

所以就涉及到不同的日期类型之间的转换，最好的方式就是写个日期工具类DateUtil:

DateUtil:

package com.jishou.util;


import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateUtil {

    // util.date转换成sql.date
    public static java.sql.Date toSqlDate(Date date){

        return  new java.sql.Date(date.getTime());
    }

    // sql.date转换成util.date
    public static Date toUtilDate(java.sql.Date date){
        return new java.util.Date(date.getTime());
    }

    //String 转换成发 util.Date
    public static Date strToUtilDate(String dateStr){

        Date date = null;
        //注意format的格式要与日期String的格式相匹配
        DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        try {
            date = sdf.parse(dateStr);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return date;
    }
    //util.Date转换为String

    public static String dateToStr(Date date){

        String dateStr = "";
        //format的格式可以任意
        DateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");

        try {
            dateStr = sdf.format(date);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return dateStr;
    }



}
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添加功能：

前台：add.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<center>
    <h1>添加学生</h1>

    <form action="add" method="post">
    <table width="50%" height="35%">
        <tr>
            <td>姓名</td>
            <td><input type="text" name="sname"></td>
        </tr>
        <tr>
            <td>年龄</td>
            <td><input type="text" name="age"></td>
        </tr>
        <tr>
            <td>生日</td>
            <td><input type="date" name="birthday"></td>
        </tr>
        <tr>
            <td>地址</td>
            <td><input type="text" name="address"></td>
        </tr>
        <tr>
            <td>头像</td>
            <td><input type="text" name="photo"></td>
        </tr>
        <tr>
            <td><input type="submit" value="添加"></td>
            <td><input type="reset" name="重置"></td>
        </tr>

    </table>
    </form>

</center>

</body>
</html>
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后台：dao层：

StudentDao：

package com.jishou.dao;

import com.jishou.pojo.Student;

import java.util.List;

public interface StudentDao {

    public List<Student> queryAllStudents();

    public int addStudent(Student student);

    public int deleteStudentById(Integer id);

    public int updateStudent(Student student);

    public Student queryOneStudentById(Integer id);
}
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StudentDaoImpl：

package com.jishou.dao;

import com.jishou.pojo.Student;
import com.jishou.util.DBUtil;
import com.jishou.util.DateUtil;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDaoImpl implements StudentDao{
    @Override
    public List<Student> queryAllStudents() {
        String sql="select * from stu";

        Connection conn = DBUtil.getConnection();
        List<Student> list = new ArrayList<>();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        try {
            pstmt= conn.prepareStatement(sql);
            rs= pstmt.executeQuery();

            while (rs.next()) {
                int id = rs.getInt(1);
                String sname = rs.getString(2);
                int age = rs.getInt(3);
                Date birthday = rs.getDate(4);
                String address = rs.getString(5);
                String photo = rs.getString(6);
                Student student = new Student(id, sname, age, birthday, address, photo);
                list.add(student);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(rs,pstmt,conn);
        }
        return list;
    }

    @Override
    public int addStudent(Student student) {
        String sql="INSERT INTO stu ( `sname`, `age`, `birthday`, `address`, `photo`) VALUES (?, ?, ?,?,?)";

        Connection conn = DBUtil.getConnection();
        PreparedStatement pstmt=null;
        int row=0;
        try {
            pstmt= conn.prepareStatement(sql);
            pstmt.setString(1,student.getSname());
            pstmt.setInt(2,student.getAge());
            pstmt.setDate(3, DateUtil.toSqlDate(student.getBirthday()));
            pstmt.setString(4,student.getAddress());
            pstmt.setString(5,student.getPhoto());
            row= pstmt.executeUpdate();

        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(pstmt,conn);
        }
        return row;
    }

    @Override
    public int deleteStudentById(Integer id) {
        String sql="delete from stu where id=?";

        Connection conn = DBUtil.getConnection();

        PreparedStatement pstmt=null;
        int row=0;
        try {
            pstmt= conn.prepareStatement(sql);

            pstmt.setInt(1,id);

            row= pstmt.executeUpdate();

        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(pstmt,conn);
        }
        return row;
    }

    @Override
    public int updateStudent(Student student) {
        String sql="UPDATE stu SET  `sname`=?, `age`=?, `birthday`=?, `address`=?, `photo`=? WHERE `id`=?";

        Connection conn = DBUtil.getConnection();
        PreparedStatement pstmt=null;
        int row=0;
        try {
            pstmt= conn.prepareStatement(sql);
            pstmt.setString(1,student.getSname());
            pstmt.setInt(2,student.getAge());
            pstmt.setDate(3, DateUtil.toSqlDate(student.getBirthday()));
            pstmt.setString(4,student.getAddress());
            pstmt.setString(5,student.getPhoto());
            pstmt.setInt(6,student.getId());
            row= pstmt.executeUpdate();

        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(pstmt,conn);
        }
        return row;
    }

    @Override
    public Student queryOneStudentById(Integer id) {
        String sql="select * from stu where id=?";

        Connection conn = DBUtil.getConnection();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        Student student=null;
        try {
            pstmt= conn.prepareStatement(sql);
            pstmt.setInt(1,id);
            rs= pstmt.executeQuery();

            if (rs.next()) {
                int idd = rs.getInt(1);
                String sname = rs.getString(2);
                int age = rs.getInt(3);
                Date birthday = rs.getDate(4);
                String address = rs.getString(5);
                String photo = rs.getString(6);
                student = new Student(idd, sname, age, birthday, address, photo);

            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(rs,pstmt,conn);
        }
        return student;
    }
}
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service层：

StudentService：

package com.jishou.service;

import com.jishou.pojo.Student;

import java.util.List;

public interface StudentService {

    public List<Student> queryAllStudents();

    public boolean addStudent(Student student);

    public boolean deleteStudentById(Integer id);

    public boolean updateStudent(Student student);

    public Student queryOneStudentById(Integer id);
}
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StudentServiceImpl：

package com.jishou.service;

import com.jishou.dao.StudentDao;
import com.jishou.dao.StudentDaoImpl;
import com.jishou.pojo.Student;

import java.util.List;

public class StudentServiceImpl implements StudentService{

    private StudentDao studentDao=new StudentDaoImpl();

    @Override
    public List<Student> queryAllStudents() {
        return studentDao.queryAllStudents();
    }

    @Override
    public boolean addStudent(Student student) {
        int row = studentDao.addStudent(student);
        if(row>0){
            return true;
        }
        return false;
    }

    @Override
    public boolean deleteStudentById(Integer id) {
        int row = studentDao.deleteStudentById(id);
        if(row>0){
            return true;
        }

        return false;
    }

    @Override
    public boolean updateStudent(Student student) {
        int row = studentDao.updateStudent(student);
        if(row>0){
            return true;
        }
        return false;
    }

    @Override
    public Student queryOneStudentById(Integer id) {
        return studentDao.queryOneStudentById(id);
    }
}
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servlet：

AddServlet：

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;
import com.jishou.util.DateUtil;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Date;

@WebServlet(name = "AddServlet",urlPatterns = "/add")
public class AddServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //取参数值
        req.setCharacterEncoding("utf-8");
        String sname = req.getParameter("sname");
        //将String的年龄转换为int类型
        Integer age = Integer.parseInt(req.getParameter("age"));
        String date = req.getParameter("birthday");
        //将String日期类型转换为java.util.Date
        Date birthday = DateUtil.strToUtilDate(date);
        String address = req.getParameter("address");
        String photo = req.getParameter("photo");

        Student student=new Student(sname,age,birthday,address,photo);
        //实现修改逻辑
        boolean flag = studentService.addStudent(student);
        if(flag){
            //添加成功
            resp.sendRedirect("list");
        }else{
            //添加失败
            resp.sendRedirect("add.jsp");
        }

    }
}
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删除功能：

前台：list.jsp:

 <a href="delete?id=<%=s.getId()%>">删除</a>
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后台：DeleteServlet：

package com.jishou.servlet;

import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "DeleteServlet",urlPatterns = "/delete")
public class DeleteServlet extends HttpServlet {
    private StudentService studentService=new StudentServiceImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //取参
        String ids = req.getParameter("id");
        //类型转换
        Integer id=Integer.parseInt(ids);

        boolean flag = studentService.deleteStudentById(id);

        if(flag){
            resp.sendRedirect("list");
        }

    }
}
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修改功能：

list.jsp:

 <a href="load?id=<%=s.getId()%>">修改</a>
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LoadServlet:

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "LoadServlet",urlPatterns = "/load")
public class LoadServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        Integer id=Integer.parseInt(req.getParameter("id"));
        //根据id查询单个
        Student student = studentService.queryOneStudentById(id);
        req.setAttribute("s",student);
        //请求转发
        req.getRequestDispatcher("update.jsp").forward(req,resp);

    }
}
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update.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<center>
    <h1>修改学生</h1>

    <form action="update" method="post">
    <table width="50%" height="35%">
        <tr>
            <td>编号</td>
            <td><input type="text" name="id" value="${s.id}" readonly></td>
        </tr>
        <tr>
            <td>姓名</td>
            <td><input type="text" name="sname" value="${s.sname}"></td>
        </tr>
        <tr>
            <td>年龄</td>
            <td><input type="text" name="age" value="${s.age}"></td>
        </tr>
        <tr>
            <td>生日</td>
            <td><input type="date" name="birthday" value="${s.birthday}"></td>
        </tr>
        <tr>
            <td>地址</td>
            <td><input type="text" name="address" value="${s.address}"></td>
        </tr>
        <tr>
            <td>头像</td>
            <td><input type="text" name="photo" value="${s.photo}"></td>
        </tr>
        <tr>
            <td><input type="submit" value="修改"></td>
            <td><input type="reset" name="重置"></td>
        </tr>

    </table>
    </form>

</center>

</body>
</html>
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UpdateServlet:

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;
import com.jishou.util.DateUtil;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Date;

@WebServlet(name = "UpdateServlet",urlPatterns = "/update")
public class UpdateServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //取参数值
        req.setCharacterEncoding("utf-8");
        Integer id = Integer.parseInt(req.getParameter("id"));
        String sname = req.getParameter("sname");
        //将String的年龄转换为int类型
        Integer age = Integer.parseInt(req.getParameter("age"));
        String date = req.getParameter("birthday");
        //将String日期类型转换为java.util.Date
        Date birthday = DateUtil.strToUtilDate(date);
        String address = req.getParameter("address");
        String photo = req.getParameter("photo");

        Student student=new Student(id,sname,age,birthday,address,photo);

        //实现修改逻辑
        boolean flag = studentService.updateStudent(student);
        if(flag){
            //修改成功
            resp.sendRedirect("list");
        }else{
            //修改失败
            resp.sendRedirect("update.jsp");
        }

    }
}
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eg7：使用Servlet实现学生信息的分页展示

编写PageBean : PageBean对象就是当前页面对象，包含了当前页面所包含的所有信息

package com.jishou.pojo;

import java.util.List;
/**
 * 存放分页相关的数据
 *
 */
public class PageBean<T> {
    //基本属性
    private int currentPageNum;//当前页数，由用户指定
    private int pageSize = 5;//每页显示的条数，固定的
    private int totalRecords;//总记录条数，数据库查出来的
    private int totalPageNum;//总页数，计算出来的
    private List<T> list;//已经分好页的结果集


    public int getCurrentPageNum() {
        return currentPageNum;
    }

    public void setCurrentPageNum(int currentPageNum) {
        this.currentPageNum = currentPageNum;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getTotalRecords() {
        return totalRecords;
    }

    public void setTotalRecords(int totalRecords) {
        this.totalRecords = totalRecords;
        //总记录数固定，页面大小固定，计算出总页数
        if(this.totalRecords%this.pageSize==0){
            this.totalPageNum=this.totalRecords/this.pageSize;
        }else{
            this.totalPageNum=this.totalRecords/this.pageSize+1;
        }
    }

    public int getTotalPageNum() {
        return totalPageNum;
    }

    public void setTotalPageNum(int totalPageNum) {
        this.totalPageNum = totalPageNum;
    }

    public List getList() {
        return list;
    }

    public void setList(List list) {
        this.list = list;
    }

    @Override
    public String toString() {
        return "PageBean{" +
                "currentPageNum=" + currentPageNum +
                ", pageSize=" + pageSize +
                ", totalRecords=" + totalRecords +
                ", totalPageNum=" + totalPageNum +
                ", list=" + list +
                '}';
    }
}


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dao层编写获取总记录数和分页查询的逻辑

StudentDao:

//查询总记录数
public int getTotalRecords();

//分页查询学生信息 参数为当前页和页面大小
public List<Student> queryStudentsByPage(int currentPage,int pageSize);
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StudentDaoImpl:

@Override
public int getTotalRecords() {
    String sql="select count(*) from stu";

    Connection conn = DBUtil.getConnection();
    PreparedStatement pstmt=null;
    ResultSet rs=null;
    int count=0;
    try {
        pstmt= conn.prepareStatement(sql);
        rs= pstmt.executeQuery();

        if (rs.next()) {
            count = rs.getInt(1);
        }
    }catch (SQLException e){
        e.printStackTrace();
    }finally {
        DBUtil.close(rs,pstmt,conn);
    }
    return count;
}

@Override
public List<Student> queryStudentsByPage(int currentPage, int pageSize) {
    String sql="select * from stu limit ?,?";

    Connection conn = DBUtil.getConnection();
    List<Student> list = new ArrayList<>();
    PreparedStatement pstmt=null;
    ResultSet rs=null;
    try {
        pstmt= conn.prepareStatement(sql);
        //注意第一个参数值的写法
        pstmt.setInt(1,(currentPage-1)*pageSize);
        pstmt.setInt(2,pageSize);
        rs= pstmt.executeQuery();

        while (rs.next()) {
            int id = rs.getInt(1);
            String sname = rs.getString(2);
            int age = rs.getInt(3);
            Date birthday = rs.getDate(4);
            String address = rs.getString(5);
            String photo = rs.getString(6);
            Student student = new Student(id, sname, age, birthday, address, photo);
            list.add(student);
        }
    }catch (SQLException e){
        e.printStackTrace();
    }finally {
        DBUtil.close(rs,pstmt,conn);
    }
    return list;
}
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service层代码

StudentService:

//分页查询学生信息 参数为当前页和页面大小
public PageBean<Student> queryStudentsByPage(int currentPage, int pageSize);
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StudentServiceImpl:

@Override
public PageBean<Student> queryStudentsByPage(int currentPage, int pageSize) {
    List<Student> students = studentDao.queryStudentsByPage(currentPage, pageSize);
    int total = studentDao.getTotalRecords();
    PageBean<Student> pageBean=new PageBean<>();
    pageBean.setPageSize(pageSize);//设置页面大小
    pageBean.setTotalRecords(total);//设置总记录数
    pageBean.setCurrentPageNum(currentPage);//设置当前页
    pageBean.setList(students);//设置当前页数据
    return pageBean;
}
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ListPageServlet 分页的Servlet

ListPageServlet:

package com.jishou.servlet;

import com.jishou.pojo.PageBean;
import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet(name = "ListPageServlet",urlPatterns = "/listpage")
public class ListPageServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //取当前页
        String currentPage= req.getParameter("currentPage");
        //第一次访问，默认currentPage 访问第一页
        if(currentPage==null) {
            currentPage = "1";
        }
        Integer currentPageNum=Integer.parseInt(currentPage);
        //页面大小暂设置成固定值3

        //分页查询所有
        PageBean<Student> pageBean = studentService.queryStudentsByPage(currentPageNum,3);
        //servlet重在业务逻辑，取值传值 jsp侧重于页面显示
        req.setAttribute("page",pageBean);
        //请求转发
        req.getRequestDispatcher("listpage.jsp").forward(req,resp);
    }
}
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注意：

登录成功之后跳转到llistpage

response.sendRedirect("listpage");
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前端 listpage.jsp

<%@ page import="com.jishou.pojo.Student" %>
<%@ page import="java.util.List" %>
<%@ page import="com.jishou.pojo.User" %>
<%@ page import="com.jishou.pojo.PageBean" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
    <style>
        #login{
            float: left;
        }
        #count{
            float: right;
        }
    </style>
</head>
<body>
<div id="login">欢迎${sessionScope.user.username}登录 <a href="logout">退出系统</a></div>
<div id="count">当前共有${applicationScope.count}人在线</div>
<center>
<h1>学生管理系统</h1>
<table width="70%" height="50%">
    <tr>
        <td>头像</td>
        <td>Id</td>
        <td>姓名</td>
        <td>年龄</td>
        <td>生日</td>
        <td>地址</td>
        <td>
            <a href="add.jsp">添加学生</a>
        </td>
    </tr>
    <c:if test="${requestScope.page!=null}">
        <c:if test="${requestScope.page.list ne null and requestScope.page.list.size() gt 0}">

            <c:forEach var="s" items="${requestScope.page.list}">
                <tr>
                    <td>
                        <img src="${s.photo}" width="20px" height="20px"/>
                    </td>
                    <td>${s.id}</td>
                    <td>${s.sname}</td>
                    <td>${s.age}</td>
                    <td>${s.birthday}</td>
                    <td>${s.address}</td>

                    <td>
                        <a href="load?id=${s.id}">修改</a>
                        <a href="delete?id=${s.id}">删除</a>
                    </td>

                </tr>
            </c:forEach>
        </c:if>

    </c:if>



    <tr>
        <td colspan="7">
            <input type="button" value="首页" onclick="toFirst()">
            <input type="button" value="上一页" onclick="toPrev()">
            当前页 ${requestScope.page.currentPageNum}| ${requestScope.page.totalPageNum} 总页数
            <input type="button" value="下一页" onclick="toNext()">
            <input type="button" value="末页" onclick="toLast()">
        </td>
    </tr>
</table>

</center>
</body>
<script>
    var currentPage=${requestScope.page.currentPageNum};
    var totalPage=${requestScope.page.totalPageNum};

    function toFirst() {
        location.href="listpage?currentPage=1";
    }
    function toPrev() {
        //控制页面显示风格
        var url="";
        if(currentPage=1){
            url="listpage?currentPage=1";
        }else{
            url="listpage?currentPage="+(currentPage-1);
        }
        location.href=url;

    }
    function toNext() {
        //控制页面显示风格
        var url="";
        if(currentPage=totalPage){
            url="listpage?currentPage="+totalPage;
        }else{
            url="listpage?currentPage="+(currentPage+1);
        }
        location.href=url;

    }
    function toLast() {
        location.href="listpage?currentPage="+${requestScope.page.totalPageNum};
    }
</script>
</html>
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浏览器访问从login.html开始访问

eg8：使用Servlet实现学生头像的上传功能

通过为表单元素设置method=“post” enctype=“multipart/form-data” 属性，让表单提交的数据以二进制编码的方式提交，在接受此请求的servlet中的二进制流来获取内容，就可以取得上传文件的内容，从而实现文件的上传。

前端页面上传表单 add.jsp

注意： form表单元素必须设置method=“post” enctype=“multipart/form-data” 属性

add.jsp

<form action="add" method="post" enctype="multipart/form-data">
<table width="50%" height="35%">
 
    <tr>
        <td>头像</td>
        <td>请选择图片：<input type="file" name="photo"></td>
    </tr>
    ........
    <tr>
        <td><input type="submit" value="添加"></td>
        <td><input type="reset" name="重置"></td>
    </tr>

</table>
</form>
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后台上传功能的实现

由于添加功能里面需要图片属性需要上传，所有上传的逻辑写在AddServlet里面了

AddServlet：

!(img\tupian.png)

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;
import com.jishou.util.DateUtil;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.UUID;

@MultipartConfig  //使用MultipartConfig注解标注改servlet能够接受文件上传的请求
@WebServlet(name = "AddServlet",urlPatterns = "/add")
public class AddServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");

        //1. 上传逻辑
        Part part = req.getPart("photo");
        //获取上传文件的文件名
        String filename=part.getSubmittedFileName();
        String serverpath="G:\\idea_workspace\\stuManage_04\\web\\img\\";
        InputStream in = part.getInputStream();
        FileOutputStream fos = new FileOutputStream(serverpath + filename);
        byte[] bytes=new byte[1024];
        int length=0;
        while((length=in.read(bytes))!=-1){
            fos.write(bytes,0,length);
        }
        fos.close();
        in.close();

		//2. 添加逻辑
        //取参数值
        String sname = req.getParameter("sname");
        //将String的年龄转换为int类型
        Integer age = Integer.parseInt(req.getParameter("age"));
        String date = req.getParameter("birthday");
        //将String日期类型转换为java.util.Date
        Date birthday = DateUtil.strToUtilDate(date);
        String address = req.getParameter("address");
        //String photo = req.getParameter("photo");
        String photo="img/"+filename;
        Student student=new Student(sname,age,birthday,address,photo);
        //实现修改逻辑
        boolean flag = studentService.addStudent(student);
        if(flag){
            //添加成功
            resp.sendRedirect("listpage");
        }else{
            //添加失败
            resp.sendRedirect("add.jsp");
        }

    }
}
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注意：如果上传之后图片没有及时更新，参考下面，修改下tomcat配置

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-oGT7j9n3-1638964004210)(img/tupian.png)]

eg9: 实现在项目中添加安全过滤器，用户未经登录不能访问系统，通过Filter统一实现设置字符编码

安全过滤器：

用户未经登录不能访问其他逻辑，所以需要Filter来实现

new —>create new Filter---->就会按模板生成

需要配置过滤路径 urlPatterns = "/" / * 表示过滤所有

思路：编写Filter，判断session中user对象是否为null；如果为null，说明未经登录，拦截，回到login.html;

但用户登录或注册时session还未创建，此时user==null；但要保证正常的登录，注册，就必须判断如果是登录或注册的话，就放行

如果login.html或者register.html中文乱码的话，把他们改成jsp文件即可

编写LoginFilter：

package com.jishou.filter;

import com.jishou.pojo.User;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebFilter(filterName = "EncodingFilter",urlPatterns = "/*")
public class LoginFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {

        HttpServletRequest request= (HttpServletRequest) req;
        HttpServletResponse response= (HttpServletResponse) resp;
        //session中取用户信息
        HttpSession session = request.getSession();
        User user = (User) session.getAttribute("user");
        //判断用户是否登录
        //获取请求路径
        String path = request.getRequestURI();
        System.out.println("path: "+path);


        if(user!=null){
        	//放行
            chain.doFilter(req, resp);
            return;
        }else {
            //登录和注册需要放行
            if (path.endsWith("login.html") || path.endsWith("register.html") || path.endsWith("login") || path.endsWith("register")) {
            	//放行
                chain.doFilter(req, resp);
                return;
            }else{
                response.sendRedirect("login.html");
            }
        }


    }

    public void init(FilterConfig config) throws ServletException {

    }

}
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2.浏览器测试访问

http://localhost:8080/stuManage_04_war_exploded/list

此时会无法访问列表，会自动重定向到login.html

字符编码过滤器：

通常处理request中的post方式的中文乱码和response中的中文乱码时，需要再servlet里面调用setCharacterEncoding()方法；可以设置过滤器，在Filter里面实现过滤，那么在servlet里面就不需要再单独设置编码了

编写CharacterFilter

package com.jishou.filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

@WebFilter(filterName = "CharacterFilter",urlPatterns = "/*")
public class CharacterFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        chain.doFilter(req, resp);
    }

    public void init(FilterConfig config) throws ServletException {

    }

}
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将Servlet里面处理中文编码的方法去掉

去掉
```
//req.setCharacterEncoding("utf-8");
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```
浏览器访问测试

eg10：通过Listener来实现统计在线人数功能：

LoginServlet和LogoutServlet里面统计在线访问人数的逻辑去掉

CountListener：

package com.jishou.listener;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.*;

@WebListener()
public class CountListener implements
         HttpSessionAttributeListener {


    private int count=0;

    public void attributeAdded(HttpSessionBindingEvent sbe) {
        HttpSession session = sbe.getSession();
        ServletContext servletContext = session.getServletContext();
        servletContext.setAttribute("count",++count);
    }

    public void attributeRemoved(HttpSessionBindingEvent sbe) {
        HttpSession session = sbe.getSession();
        ServletContext servletContext = session.getServletContext();
        servletContext.setAttribute("count",--count);
    }

    public void attributeReplaced(HttpSessionBindingEvent sbe) {
      /* This method is invoked when an attribute
         is replaced in a session.
      */
    }
}
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eg10: 使用jquery+ajax实现添加用户时自动检查用户名是否已存在，并给予相应提示功能

add.jsp里面使用jquery+ajax异步访问后台

需要引入jquery的库文件，放在web/js目录底下 jquery-1.8.3.js

add.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<script src="js/jquery-1.8.3.js"></script>
<script>
    function checkName() {

        var sname=$("#sname").val();
        console.log(sname);
        $.post(		//使用post请求
            'checkName',  //访问后台的url路径
            {"sname":sname},//往后台传的参数
             //回调函数 就使后台执行完毕之后再执行的函数  data表示后台执行的结果，返回的值
             function (data) {
                console.log(data);
                if(data==1){
                    //用户名存在
                    $("#ff").html("用户名已存在！！！请重新输入...")
                }else{
                    $("#ff").html("该用户名不存在！！！可以使用...")
                }

             }

        )
    }
</script>
<body>

<center>
    <h1>添加学生</h1>

    <form action="add" method="post" enctype="multipart/form-data">
    <table width="50%" height="35%">
        <tr>
            <td>姓名</td>
            <td><input type="text" name="sname" id="sname" onblur="checkName()">
            <font id="ff" color="red" size="2"></font>
            </td>
        </tr>
      ........

    </table>
    </form>

</center>

</body>
</html>
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说明：

$("#sname") 表示取得id="sname"的标签对象 .val() 取该对象的value值

$.post() 是通过jquery来实现ajax异步和后台交互使用post请求方式

$("#ff").html(" ") 表示往id="ff"的标签中间写入相应内容

οnblur="" 光标丢失事件

后台servlet编写代码

CheckSnameServlet

package com.jishou.servlet;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "CheckSnameServlet",urlPatterns = "/checkName")
public class CheckSnameServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1. 取参数值
        req.setCharacterEncoding("utf-8");
        String sname = req.getParameter("sname");
        //2.连数据库查询
        //true 存在 false不存在
        boolean flag= studentService.queryStudentBySname(sname);
        //3.响应  必须输出到浏览器页面上
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter out = resp.getWriter();
        if(flag){
            //用户名存在
            out.println(1);
        }else {
            //用户名不存在
            out.println(0);
        }

        out.flush();
        out.close();
    }
}
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后台service接口及其实现类

StudentService

//判断用户名是否存在
public boolean queryStudentBySname(String sname);
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StudentServiceImpl

@Override
public boolean queryStudentBySname(String sname) {
    return studentDao.queryStudentBySname(sname);
}
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后台dao接口及其实现类

StudentDao：

//判断用户名是否存在
public boolean queryStudentBySname(String sname);
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StudentDaoImpl

@Override
public boolean queryStudentBySname(String sname) {
    String sql="select * from stu where sname=?";

    Connection conn = DBUtil.getConnection();
    PreparedStatement pstmt=null;
    ResultSet rs=null;
    Student student=null;
    try {
        pstmt= conn.prepareStatement(sql);
        pstmt.setString(1,sname);
        rs= pstmt.executeQuery();

        if (rs.next()) {
           return true;

        }
    }catch (SQLException e){
        e.printStackTrace();
    }finally {
        DBUtil.close(rs,pstmt,conn);
    }
    return false;
}
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浏览器访问测试效果

在add.jsp里面输入用户名后，光标丢失，就会自动判断输入的用户名是否存在，并给予提示

eg11：实现首页上左右布局：

创建index.jsp head.jsp left.jsp

使用frameset实现页面布局

index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>


<frameset rows="15%,*" border="1">
    <frame src="head.jsp">
    <!-- 引用左边和主体部分 -->
    <frameset  cols="18%,*" border="1">
        <frame src="left.jsp" name="leftmenu">
        <frame src="main.jsp" name="main">
    </frameset>
</frameset>

</html>
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head.jsp

可以在head.jsp放些公司logo；欢迎XXX

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<div id="login">欢迎${sessionScope.user.username}登录 </div>
<div id="count">当前共有${applicationScope.count}人在线</div>
</body>
</html>
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left.jsp:

注意：学生列表和添加学生超链接执向的地址，和target="main"的值，要在name="main"那个frame里面呈现

<a href="logout" target="_parent">退出系统</a>  target="_parent"  表示调到父组件
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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<div>
    <a href="#" target="main">首页</a>
    <dl>
        <dt>
            学生管理
        </dt>
        <dd>
            <a href="listpage" target="main">学生列表</a>
        </dd>
        <dd>
            <a href="add.jsp" target="main">添加学生</a>
        </dd>
    </dl>
    <dl>
        <dt>
            班级管理
        </dt>
        <dd>
            <a href="" target="main">班级列表</a>
        </dd>
        <dd>
            <a href="" target="main">添加班级</a>
        </dd>
    </dl>
    <dl>
        <dt>
            系统管理
        </dt>
        <dd>
            <a href="" target="main">修改密码</a>
        </dd>
        <dd>
            <a href="logout" target="_parent">退出系统</a>
        </dd>
    </dl>
</div>
</body>
</html>
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LoginServlet：登录成功之后直接跳到首页

response.sendRedirect("index.jsp");
1

eg12：实现正则验证：

在register.jsp里面设计常用的几个字段：手机号码，身份证号码，邮箱等，通过正则表达式实现验证：

正则语法可以参考菜鸟教程：

https://www.runoob.com/regexp/regexp-tutorial.html

需要引入jquery文件：οnblur="" 光标丢失事件


<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<script type="text/javascript" src="js/jquery-1.8.3.js"></script>
<script type="text/javascript">
    function checkUserName(){
        var username = $("input[name='username']").val();
        var pattern=/^.{6,20}$/;// 6-20个字符组成
        if(!pattern.test(username)){
            alert("用户名长度必须是6-20个字符组成");
        }
    }

    function checkPassword(){
        var password = $("input[name='password']").val();
        var pattern=/^[a-zA-Z]\w{5,17}$/;// 以字母开头，长度在6~18之间，只能包含字母、数字和下划线
        if(!pattern.test(password)){
            alert("密码必须以字母开头，长度在6~18之间，只能包含字母、数字和下划线");
        }
    }

    function checkPhone(){
        var phone = $("input[name='phone']").val();
        var pattern=/^(13[0-9]|14[5|7]|15[0|1|2|3|5|6|7|8|9]|18[0|1|2|3|5|6|7|8|9])\d{8}$/;// 11位手机号码
        if(!pattern.test(phone)){
            alert("请输入正确的手机号码格式");
        }
    }
    function checkIdCard(){
        var idCard = $("input[name='idcard']").val();
        var pattern=/^\d{15}|\d{18}$/;// 15或18位身份证号码
        if(!pattern.test(idCard)){
            alert("请输入正确的身份证号码格式");
        }
    }
    function checkEmail(){
        var email = $("input[name='email']").val();
        var pattern=/^[A-Za-z0-9\u4e00-\u9fa5]+@[a-zA-Z0-9_-]+(\.[a-zA-Z0-9_-]+)+$/;// 邮箱格式
        if(!pattern.test(email)){
            alert("请输入正确的邮箱号码格式");
        }
    }

</script>
<body>
<h1>注册页面</h1>
<!--前端访问路径都不加/ -->
<form action="register" method="post">
    用户名： <input type="text" name="username" onblur="checkUserName()"><br>
    密码： <input type="password" name="password" onblur="checkPassword()"><br>
    手机号码： <input type="text" name="phone" onblur="checkPhone()"><br>
    身份证号码： <input type="text" name="idcard" onblur="checkIdCard()"><br>
    邮箱：  <input type="text" name="email" onblur="checkEmail()"><br>
    <input type="submit" value="注册">
</form>

</body>
</html>
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附：正则表达式大全

一、校验数字的表达式


1. 数字：^[0-9]*$

2. n位的数字：^\d{n}$

3. 至少n位的数字：^\d{n,}$

4. m-n位的数字：^\d{m,n}$

5. 零和非零开头的数字：^(0|[1-9][0-9]*)$

6. 非零开头的最多带两位小数的数字：^([1-9][0-9]*)+(.[0-9]{1,2})?$

7. 带1-2位小数的正数或负数：^(\-)?\d+(\.\d{1,2})?$

8. 正数、负数、和小数：^(\-|\+)?\d+(\.\d+)?$

9. 有两位小数的正实数：^[0-9]+(.[0-9]{2})?$

10. 有1~3位小数的正实数：^[0-9]+(.[0-9]{1,3})?$

11. 非零的正整数：^[1-9]\d*$ 或 ^([1-9][0-9]*){1,3}$ 或 ^\+?[1-9][0-9]*$

12. 非零的负整数：^\-[1-9][]0-9"*$ 或 ^-[1-9]\d*$

13. 非负整数：^\d+$ 或 ^[1-9]\d*|0$

14. 非正整数：^-[1-9]\d*|0$ 或 ^((-\d+)|(0+))$

15. 非负浮点数：^\d+(\.\d+)?$ 或 ^[1-9]\d*\.\d*|0\.\d*[1-9]\d*|0?\.0+|0$

16. 非正浮点数：^((-\d+(\.\d+)?)|(0+(\.0+)?))$ 或 ^(-([1-9]\d*\.\d*|0\.\d*[1-9]\d*))|0?\.0+|0$

17. 正浮点数：^[1-9]\d*\.\d*|0\.\d*[1-9]\d*$ 或 ^(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*))$

18. 负浮点数：^-([1-9]\d*\.\d*|0\.\d*[1-9]\d*)$ 或 ^(-(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*)))$

19. 浮点数：^(-?\d+)(\.\d+)?$ 或 ^-?([1-9]\d*\.\d*|0\.\d*[1-9]\d*|0?\.0+|0)$

二、校验字符的表达式

1. 汉字：^[\u4e00-\u9fa5]{0,}$

2. 英文和数字：^[A-Za-z0-9]+$ 或 ^[A-Za-z0-9]{4,40}$

3. 长度为3-20的所有字符：^.{3,20}$

4. 由26个英文字母组成的字符串：^[A-Za-z]+$

5. 由26个大写英文字母组成的字符串：^[A-Z]+$

6. 由26个小写英文字母组成的字符串：^[a-z]+$

7. 由数字和26个英文字母组成的字符串：^[A-Za-z0-9]+$

8. 由数字、26个英文字母或者下划线组成的字符串：^\w+$ 或 ^\w{3,20}$

9. 中文、英文、数字包括下划线：^[\u4E00-\u9FA5A-Za-z0-9_]+$

10. 中文、英文、数字但不包括下划线等符号：^[\u4E00-\u9FA5A-Za-z0-9]+$ 或 ^[\u4E00-\u9FA5A-Za-z0-9]{2,20}$

11. 可以输入含有^%&',;=?$\"等字符：[^%&',;=?$\x22]+ 12 禁止输入含有~的字符：[^~\x22]+

三、特殊需求表达式

1. Email地址：^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$

2. 域名：[a-zA-Z0-9][-a-zA-Z0-9]{0,62}(/.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+/.?

3. InternetURL：[a-zA-z]+://[^\s]* 或 ^http://([\w-]+\.)+[\w-]+(/[\w-./?%&=]*)?$

4. 手机号码：^(13[0-9]|14[5|7]|15[0|1|2|3|5|6|7|8|9]|18[0|1|2|3|5|6|7|8|9])\d{8}$

5. 电话号码("XXX-XXXXXXX"、"XXXX-XXXXXXXX"、"XXX-XXXXXXX"、"XXX-XXXXXXXX"、"XXXXXXX"和"XXXXXXXX)：^(\(\d{3,4}-)|\d{3.4}-)?\d{7,8}$

6. 国内电话号码(0511-4405222、021-87888822)：\d{3}-\d{8}|\d{4}-\d{7}

7. 身份证号(15位、18位数字)：^\d{15}|\d{18}$

8. 短身份证号码(数字、字母x结尾)：^([0-9]){7,18}(x|X)?$ 或 ^\d{8,18}|[0-9x]{8,18}|[0-9X]{8,18}?$

9. 帐号是否合法(字母开头，允许5-16字节，允许字母数字下划线)：^[a-zA-Z][a-zA-Z0-9_]{4,15}$

10. 密码(以字母开头，长度在6~18之间，只能包含字母、数字和下划线)：^[a-zA-Z]\w{5,17}$

11. 强密码(必须包含大小写字母和数字的组合，不能使用特殊字符，长度在8-10之间)：^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$

12. 日期格式：^\d{4}-\d{1,2}-\d{1,2}

13. 一年的12个月(01～09和1～12)：^(0?[1-9]|1[0-2])$

14. 一个月的31天(01～09和1～31)：^((0?[1-9])|((1|2)[0-9])|30|31)$

15. 钱的输入格式：
16. 1.有四种钱的表示形式我们可以接受:"10000.00" 和 "10,000.00", 和没有 "分" 的 "10000" 和 "10,000"：^[1-9][0-9]*$
17. 2.这表示任意一个不以0开头的数字,但是,这也意味着一个字符"0"不通过,所以我们采用下面的形式：^(0|[1-9][0-9]*)$
18. 3.一个0或者一个不以0开头的数字.我们还可以允许开头有一个负号：^(0|-?[1-9][0-9]*)$
19. 4.这表示一个0或者一个可能为负的开头不为0的数字.让用户以0开头好了.把负号的也去掉,因为钱总不能是负的吧.下面我们要加的是说明可能的小数部分：^[0-9]+(.[0-9]+)?$
20. 5.必须说明的是,小数点后面至少应该有1位数,所以"10."是不通过的,但是 "10" 和 "10.2" 是通过的：^[0-9]+(.[0-9]{2})?$
21. 6.这样我们规定小数点后面必须有两位,如果你认为太苛刻了,可以这样：^[0-9]+(.[0-9]{1,2})?$

22. 7.这样就允许用户只写一位小数.下面我们该考虑数字中的逗号了,我们可以这样：^[0-9]{1,3}(,[0-9]{3})*(.[0-9]{1,2})?$

23 8.1到3个数字,后面跟着任意个 逗号+3个数字,逗号成为可选,而不是必须：^([0-9]+|[0-9]{1,3}(,[0-9]{3})*)(.[0-9]{1,2})?$

24. 备注：这就是最终结果了,别忘了"+"可以用"*"替代如果你觉得空字符串也可以接受的话(奇怪,为什么?)最后,别忘了在用函数时去掉去掉那个反斜杠,一般的错误都在这里

25. xml文件：^([a-zA-Z]+-?)+[a-zA-Z0-9]+\\.[x|X][m|M][l|L]$

26. 中文字符的正则表达式：[\u4e00-\u9fa5]

27. 双字节字符：[^\x00-\xff] (包括汉字在内，可以用来计算字符串的长度(一个双字节字符长度计2，ASCII字符计1))

28. 空白行的正则表达式：\n\s*\r (可以用来删除空白行) 

29. HTML标记的正则表达式：<(\S*?)[^>]*>.*?</\1>|<.*? /> (网上流传的版本太糟糕，上面这个也仅仅能部分，对于复杂的嵌套标记依旧无能为力) 

30. 首尾空白字符的正则表达式：^\s*|\s*$或(^\s*)|(\s*$) (可以用来删除行首行尾的空白字符(包括空格、制表符、换页符等等)，非常有用的表达式)

31. 腾讯QQ号：[1-9][0-9]{4,} (腾讯QQ号从10000开始)

32. 中国邮政编码：[1-9]\d{5}(?!\d) (中国邮政编码为6位数字)

33. IP地址：\d+\.\d+\.\d+\.\d+ (提取IP地址时有用)

34. IP地址：((?:(?:25[0-5]|2[0-4]\\d|[01]?\\d?\\d)\\.){3}(?:25[0-5]|2[0-4]\\d|[01]?\\d?\\d))

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eg13: 使用cookie完成记住密码功能和异步登录功能

注意：如果访问login.jsp,浏览器页面提示js文件访问不到404的话，可以吧js目录删掉再重新新建一下，再把js文件放进去

注意：需要引入3个js文件

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<script type="text/javascript" src="js/jquery-1.8.3.js"></script>
<script type="text/javascript" src="js/jquery.cookie.js"></script>
<script type="text/javascript" src="js/jquery.base64.js"></script>
<script type="text/javascript">

    //设置cookie
    function setCookie(){
        var loginCode = $("#zhanghao").val(); //获取用户名信息
        var pwd = $("#mima").val(); //获取登陆密码信息
        var checked = $("input[type='checkbox']").is(':checked');//获取“是否记住密码”复选框
        //console.log("setCookie方法是否记住密码："+checked);
        if(checked){ //判断是否选中了“记住密码”复选框
            //设置cookie过期时间
            var date = new Date();
            date.setTime(date.getTime()+60*1000);//只能这么写，60表示60秒钟
            //console.log("cookie过期时间："+date);
            $.cookie("login_code",loginCode,{ expires: date, path: '/' });//调用jquery.cookie.js中的方法设置cookie中的用户名
            $.cookie("pwd",$.base64.encode(pwd),{ expires: date, path: '/' });//调用jquery.cookie.js中的方法设置cookie中的登陆密码，并使用base64（jquery.base64.js）进行加密
        }else{
            $.cookie("login_code", null);
            $.cookie("pwd", null);
        }
    }

    //清除所有cookie函数
    function clearAllCookie() {
        var date=new Date();
        date.setTime(date.getTime()-10000);
        var keys=document.cookie.match(/[^ =;]+(?=\=)/g);
        console.log("需要删除的cookie名字："+keys);
        if (keys) {
            for (var i =  keys.length; i--;)
                document.cookie=keys[i]+"=0; expire="+date.toGMTString()+"; path=/";
        }
    }
    //获取cookie
    function getCookie(){
        var loginCode = $.cookie("login_code"); //获取cookie中的用户名
        var pwd =  $.cookie("pwd"); //获取cookie中的登陆密码
        console.log("获取cookie:账户："+loginCode);
        console.log("获取cookie:密码："+pwd);
        if (!loginCode||loginCode==0) {
            console.log("账户："+!loginCode);
            //alert("请输出内容！");
        }else{
            $("#zhanghao").val(loginCode);
        }
        if(!pwd||pwd==0){
            console.log("密码："+!pwd);
        }else{
            //密码存在的话把密码填充到密码文本框
            //console.log("密码解密后："+$.base64.decode(pwd));
            $("#mima").val($.base64.decode(pwd));
            //密码存在的话把“记住用户名和密码”复选框勾选住
            $("[name='jizhu']").attr("checked","true");
        }

    }
    function checkLogin(){
        var userName = $('#zhanghao').val();
        console.log("用户名："+userName);
        if(userName == ''){
            alert("请输入用户名。");
            return;
        }
        var userPass =$('#mima').val();
        console.log("密码："+userPass);
        if(userPass == ''){
            alert("请输入密码。");
            return;
        }
        //判断是否选中复选框，如果选中，添加cookie
        var jizhupwd=$("input[type='checkbox']").is(':checked');
        console.log("是否记住密码："+jizhupwd);
        if(jizhupwd){
            //添加cookie
            setCookie();
        }else{
            clearAllCookie();
        }
        login(userName,userPass);//联网上传账号密码
    }
    //异步登录逻辑
    function login(username,password){
        console.log(username+"  "+password);
        $.post(
            "login",
            {
                "username": username,
                "password": password,
            },
            function(data) {
                    if (data == 1) {
                        alert("登录成功");
                        location.href = "index.jsp";
                    } else {
                        alert("登录失败");
                    }

            }

        );


    }

</script>
<body onload="getCookie()">

<h1>登录页面</h1>

<!--前端访问路径都不加/ -->
<form>
    用户名： <input type="text" name="username" id="zhanghao"><br>
    密码： <input type="password" name="password" id="mima"><br>
    <input type="checkbox" name="jizhu">记住密码<br>
    <input type="button" value="登录" id="denglu" onclick="checkLogin()">
    <a href="register.jsp">立即注册</a>

</form>

</body>
</html>
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LoginServlet改造：

package com.jishou.servlet;

import com.jishou.pojo.User;
import com.jishou.service.UserService;
import com.jishou.service.UserServiceImpl;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    private UserService userService=new UserServiceImpl();

    //private Integer count=0;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 取前台参数
        //request.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        User qtuser=new User(username,password);
        //2. 连接数据库查询
        User htuser = userService.login(qtuser);
        //3. 判断登录是否成功
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        if(htuser!=null){
            HttpSession session = request.getSession();
            session.setAttribute("user",htuser);
            out.println(1);
        }else{
            out.println(0);
        }
        out.flush();
        out.close();



    }
}
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eg14: 批量删除功能

listpage.jsp

该页面里面需要写生全选，反选，全不选的实现逻辑，并且获取选中的id值，拼接成字符串，并通过ajax实现批量删除的逻辑

$(function(){}) 是jquery里面的文档就绪函数，表示页面加载完毕就执行的逻辑，相当于js的window.onload事件；

最后将选中的id值直接作为字符串拼接；比如选中2和3；那参数ids=2,3

<script type="text/javascript" src="js/jquery-1.8.3.js"></script>
<script>

    $(
        function () {
            //全选
            $("#qx").click(

                function(){
                    $(".one").attr("checked",true);
                }
            ),
            //全不选
            $("#qbx").click(

                function(){
                    $(".one").attr("checked",false);
                }
            ),
            //反选
            $("#fx").click(

                function(){
                    $(".one").each(function(){

                        $(this).attr("checked",!$(this).attr("checked"));

                    })
                }
            )
        }
    )
    //批量删除
    function plsc(){
        var ids="";
        $(".one:checked").each(
            function(){
                var id=$(this).val();
                ids+=","+id;
            }
        )
        ids=ids.substring(1);
        console.log("ids="+ids);
        $.post(
            'deleteplsc',
            {ids:ids},
            function(obj){
                if(obj==1){
                    alert("删除成功");
                    location="listpage";
                }else{
                    alert("删除失败");
                }
            },
            'json'

        )

    }
</script>


    <div>
        <input type="button" value="批量删除" onclick="plsc()">
    </div>

    <tr>
        <td>
            <input type="button" id="qx" value="全选" >
            <input type="button" id="qbx" value="全不选">
            <input type="button" id="fx" value="反选">
        </td>
       ........
    </tr>
 

            <c:forEach var="s" items="${requestScope.page.list}">

                <tr>
                    <td>
                        <input type="checkbox" class="one" value="${s.id }">
                    </td>
            </c:forEach>
         。。。。。。。
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listpage.jsp 完整代码如下：

<%@ page import="com.jishou.pojo.Student" %>
<%@ page import="java.util.List" %>
<%@ page import="com.jishou.pojo.User" %>
<%@ page import="com.jishou.pojo.PageBean" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
    <style>
        #login{
            float: left;
        }
        #count{
            float: right;
        }
    </style>
</head>
<body>
<script type="text/javascript" src="js/jquery-1.8.3.js"></script>
<script>

    $(
        function () {
            //全选
            $("#qx").click(

                function(){
                    $(".one").attr("checked",true);
                }
            ),
            //全不选
            $("#qbx").click(

                function(){
                    $(".one").attr("checked",false);
                }
            ),
            //反选
            $("#fx").click(

                function(){
                    $(".one").each(function(){

                        $(this).attr("checked",!$(this).attr("checked"));

                    })
                }
            )
        }
    )
    //批量删除
    function plsc(){
        var ids="";
        $(".one:checked").each(
            function(){
                var id=$(this).val();
                ids+=","+id;
            }
        )
        ids=ids.substring(1);
        console.log("ids="+ids);
        $.post(
            'deleteplsc',
            {ids:ids},
            function(obj){
                if(obj==1){
                    alert("删除成功");
                    location="listpage";
                }else{
                    alert("删除失败");
                }
            },
            'json'

        )

    }
</script>


<center>
<h1>学生管理系统</h1>
    <div>
        <input type="button" value="批量删除" onclick="plsc()">
    </div>
<table width="70%" height="50%">
    <tr>
        <td>
            <input type="button" id="qx" value="全选" >
            <input type="button" id="qbx" value="全不选">
            <input type="button" id="fx" value="反选">
        </td>
        <td>头像</td>
        <td>Id</td>
        <td>姓名</td>
        <td>年龄</td>
        <td>生日</td>
        <td>地址</td>
        <td>
            <a href="add.jsp">添加学生</a>
        </td>
    </tr>
    <c:if test="${requestScope.page!=null}">
        <c:if test="${requestScope.page.list ne null and requestScope.page.list.size() gt 0}">

            <c:forEach var="s" items="${requestScope.page.list}">

                <tr>
                    <td>
                        <input type="checkbox" class="one" value="${s.id }">
                    </td>
                    <td>
                        <img src="${s.photo}" width="20px" height="20px"/>
                    </td>
                    <td>${s.id}</td>
                    <td>${s.sname}</td>
                    <td>${s.age}</td>
                    <td>${s.birthday}</td>
                    <td>${s.address}</td>

                    <td>
                        <a href="load?id=${s.id}">修改</a>
                        <a href="delete?id=${s.id}">删除</a>
                    </td>

                </tr>
            </c:forEach>
        </c:if>

    </c:if>



    <tr>
        <td colspan="7">
            <input type="button" value="首页" onclick="toFirst()">
            <input type="button" value="上一页" onclick="toPrev()">
            当前页 ${requestScope.page.currentPageNum}| ${requestScope.page.totalPageNum} 总页数
            <input type="button" value="下一页" onclick="toNext()">
            <input type="button" value="末页" onclick="toLast()">
        </td>
    </tr>
</table>

</center>
</body>
<script>
    var currentPage=${requestScope.page.currentPageNum};
    var totalPage=${requestScope.page.totalPageNum};

    function toFirst() {
        location.href="listpage?currentPage=1";
    }
    function toPrev() {
        //控制页面显示风格
        var url="";
        if(currentPage=1){
            url="listpage?currentPage=1";
        }else{
            url="listpage?currentPage="+(currentPage-1);
        }
        location.href=url;

    }
    function toNext() {
        //控制页面显示风格
        var url="";
        if(currentPage=totalPage){
            url="listpage?currentPage="+totalPage;
        }else{
            url="listpage?currentPage="+(currentPage+1);
        }
        location.href=url;

    }
    function toLast() {
        location.href="listpage?currentPage="+${requestScope.page.totalPageNum};
    }
</script>
</html>
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后台：

DeletePlscServlet：

package com.jishou.servlet;

import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "DeletePlscServlet",urlPatterns = "/deleteplsc")
public class DeletePlscServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String ids = req.getParameter("ids");
        System.out.println("ids: "+ids);

        boolean flag=studentService.deleteStudentByBatch(ids);
        PrintWriter out = resp.getWriter();
        if(flag){
            out.println(1);
        }else{
            out.println(0);
        }
        out.flush();
        out.close();
    }
}
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StudentService：

//批量删除
public boolean deleteStudentByBatch(String ids);
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StudentServiceImpl：

@Override
public boolean deleteStudentByBatch(String ids) {
    String[] idStr = ids.split(",");
    int row=0;
    for(String id:idStr){
        row = studentDao.deleteStudentById(Integer.parseInt(id));
    }
    if(row>0){
        return true;
    }
    return false;
}
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eg15: 模糊查询和区间查询功能

方便起见，在这里面直接模糊查询和区间查询没有分页，直接写在list.jsp了

list.jsp：

在table表格上面写生查询的表单：根据姓名模糊查询和根据生日区间查询

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
    <style>
        #login{
            float: left;
        }
        #count{
            float: right;
        }
    </style>
</head>
<script type="text/javascript" src="js/jquery-1.8.3.js"></script>
<script>
    $(function () {
        //日期框设置默认值
        var time = new Date();
        var day = ("0" + time.getDate()).slice(-2);
        var month = ("0" + (time.getMonth() + 1)).slice(-2);
        var today = time.getFullYear() + "-" + (month) + "-" + (day);
        $('#begin').val(today);
        $('#end').val(today);
    })
</script>
<body>
<%
    List<Student> list = (List<Student>) request.getAttribute("list");
    User user = (User) request.getSession().getAttribute("user");
%>
<div id="login">欢迎<%=user.getUsername()%>登录 <a href="logout">退出系统</a></div>
<div id="count">当前共有<%=application.getAttribute("count")%>人在线</div>
<center>
<h1>学生管理系统</h1>
<form action="condition" method="post">
    姓名： <input type="text" name="name" value="${c.name}">
    开始时间： <input type="date" name="begin" id="begin">
    结束时间： <input type="date" name="end" id="end">
    <input type="submit" value="搜索">
</form>
<table width="70%" height="50%">
    ..............
</table>
</center>
</body>
</html>

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Condition：

由于查询的条件有多个，为了方便起见，将查询的条件封装在对象Condition里面，pojo包里面

package com.jishou.pojo;

import java.util.Date;

public class Condition {

    private String name;
    private Date begin;//开始时间
    private Date end;//结束时间

    public Condition() {
    }

    public Condition(String name, Date begin, Date end) {
        this.name = name;
        this.begin = begin;
        this.end = end;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Date getBegin() {
        return begin;
    }

    public void setBegin(Date begin) {
        this.begin = begin;
    }

    public Date getEnd() {
        return end;
    }

    public void setEnd(Date end) {
        this.end = end;
    }

    @Override
    public String toString() {
        return "Condition{" +
                "name='" + name + '\'' +
                ", begin=" + begin +
                ", end=" + end +
                '}';
    }
}
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ConditionServlet：

package com.jishou.servlet;

import com.jishou.pojo.Condition;
import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;
import com.jishou.util.DateUtil;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Date;
import java.util.List;

@WebServlet(name = "ConditionServlet",urlPatterns = "/condition")
public class ConditionServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        String name = req.getParameter("name");
        Date begin = DateUtil.strToUtilDate(req.getParameter("begin"));
        Date end = DateUtil.strToUtilDate(req.getParameter("end"));

        Condition condition=new Condition(name,begin,end);
        List<Student> students= studentService.queryStudentsByCondition(condition);

        //servlet重在业务逻辑，取值传值 jsp侧重于页面显示
        req.setAttribute("list",students);
        req.setAttribute("c",condition);
        //请求转发
        req.getRequestDispatcher("list.jsp").forward(req,resp);


    }
}
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StudentService：

//条件查询
public List<Student> queryStudentsByCondition(Condition condition);
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StudentServiceImpl：

@Override
public List<Student> queryStudentsByCondition(Condition condition) {
    return studentDao.queryStudentsByCondition(condition);
}
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StudentDao：

//条件查询
public List<Student> queryStudentsByCondition(Condition condition);
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StudentDaoImpl：

@Override
public List<Student> queryStudentsByCondition(Condition condition) {

    String sql="";

    Connection conn = DBUtil.getConnection();
    List<Student> list = new ArrayList<>();
    PreparedStatement pstmt=null;
    ResultSet rs=null;
    try {
        String name = condition.getName();
        //判断要不要根据姓名模糊查询
        if(name!=null&&!"".equals(name)){
            sql="select * from stu where sname like ? and birthday between ? and ?";
            pstmt= conn.prepareStatement(sql);
            pstmt.setString(1,"%"+name+"%");
            pstmt.setDate(2,DateUtil.toSqlDate(condition.getBegin()));
            pstmt.setDate(3,DateUtil.toSqlDate(condition.getEnd()));
        }else{
            sql="select * from stu where  birthday between ? and ?";
            pstmt= conn.prepareStatement(sql);
            pstmt.setDate(1,DateUtil.toSqlDate(condition.getBegin()));
            pstmt.setDate(2,DateUtil.toSqlDate(condition.getEnd()));
        }

        rs= pstmt.executeQuery();

        while (rs.next()) {
            int id = rs.getInt(1);
            String sname = rs.getString(2);
            int age = rs.getInt(3);
            Date birthday = rs.getDate(4);
            String address = rs.getString(5);
            String photo = rs.getString(6);
            Student student = new Student(id, sname, age, birthday, address, photo);
            list.add(student);
        }
    }catch (SQLException e){
        e.printStackTrace();
    }finally {
        DBUtil.close(rs,pstmt,conn);
    }
    return list;
}
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eg16: 实现往数据库中批量导入100条数据

这里直接使用单元测试：

TestInsertBatch：

package com.jishou.test;

import com.jishou.pojo.Student;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;
import org.junit.Test;

import java.sql.Timestamp;
import java.util.Date;

public class TestInsertBatch {

    StudentService studentService=new StudentServiceImpl();

    @Test
    public void testInsertBatch(){


        String[] xing={"周","吴","郑","王","赵","钱","孙","李","张","陶","宋"};
        String[] ming={"小米","小明","小刚","小花","小杰","小利","花花","小美"};
        String[] address={"北京","洛阳","深圳","郑州","香港"};

        for(int i=0;i<100;i++){
            int xingIndex=(int)(Math.random()*(xing.length-1)+1);
            int mingIndex=(int)(Math.random()*(ming.length-1)+1);
            int addressIndex=(int)(Math.random()*(address.length-1)+1);
            int age=(int)(Math.random()*(100)+1);
            Date birthday=randomDate();
            Student s=new Student(xing[xingIndex]+ming[mingIndex],age,birthday,address[addressIndex],"");
            System.out.println(s);
            studentService.addStudent(s);
        }


    }
    //获取随机的日期类型的值
    public static Date randomDate() {
        int startYear=2016;                            //指定随机日期开始年份
        int endYear=2018;                          //指定随机日期开始年份(含)
        long start = Timestamp.valueOf(startYear+1+"-1-1 0:0:0").getTime();
        long end = Timestamp.valueOf(endYear+"-1-1 0:0:0").getTime();
        long ms=(long) ((end-start)*Math.random()+start);  //获得了符合条件的13位毫秒数
        Date birthday=new Date(ms);
        return birthday;
    }

}
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直接运行testInsertBatch() 方法即可

eg17: 实现通过Echarts图表实现相同地域的学生个数的饼状图显示

在这里使用图表插件echarts

参考

官方文档demo: https://echarts.apache.org/examples/zh/index.html

Echarts菜鸟教程： https://www.runoob.com/echarts/echarts-tutorial.html

需要吧echarts的库文件echarts.min.js放到web的js目录底下

还需要复制fastjson-1.2.46.jar的依赖到lib目录底下，这个依赖能够实现json数据和java对象之间的转换

前端;

tubiao.jsp:

在这里，echarts里面的数据来自于后台，但数据格式是json格式的，属性必须叫name和value

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<script type="text/javascript" src="js/echarts.min.js"></script>
<body>
${list}
<!-- 为ECharts准备一个具备大小（宽高）的Dom -->
<div id="main" style="width: 600px;height:400px;"></div>
<script type="text/javascript">
    // 基于准备好的dom，初始化echarts实例
    var myChart = echarts.init(document.getElementById('main'));

    myChart.setOption({
        series : [
            {
                name: '访问来源',
                type: 'pie',    // 设置图表类型为饼图
                radius: '55%',  // 饼图的半径，外半径为可视区尺寸（容器高宽中较小一项）的 55% 长度。
                data: ${list}
                /*[          // 数据数组，name 为数据项名称，value 为数据项值
                    {value:235, name:'视频广告'},
                    {value:274, name:'联盟广告'},
                    {value:310, name:'邮件营销'},
                    {value:335, name:'直接访问'},
                    {value:400, name:'搜索引擎'}
                ]*/
            }
        ]
    })
</script>

</body>
</html>
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从后台查询出数据，List集合，但需要转换成json数据格式，使用fastjson里面的方法

echarts属性名必须叫name和value,所以封装一个javabean对象EchartsBean：

pojo实体类：

EchartsBean：

package com.jishou.pojo;

public class EchartsBean {
    String name;
    int value;

    public EchartsBean() {
    }

    public EchartsBean(String name, int value) {
        this.name = name;
        this.value = value;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getValue() {
        return value;
    }

    public void setValue(int value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "EchartsBean{" +
                "name='" + name + '\'' +
                ", value='" + value + '\'' +
                '}';
    }
}
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dao层：

StudentDao：

//根据地址分组，查询各个区域的学生个数
public List<EchartsBean> findCountByAddress();
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StudentDaoImpl：

@Override
public List<EchartsBean> findCountByAddress() {
    String sql="select address,COUNT(*) from stu group by address";

    Connection conn = DBUtil.getConnection();
    PreparedStatement pstmt=null;
    ResultSet rs=null;
    List<EchartsBean> list=new ArrayList<>();
    try {
        pstmt= conn.prepareStatement(sql);
        rs= pstmt.executeQuery();

        while (rs.next()) {
            String address = rs.getString(1);
            int count = rs.getInt(2);
            EchartsBean echarts=new EchartsBean(address,count);
            list.add(echarts);
        }
    }catch (SQLException e){
        e.printStackTrace();
    }finally {
        DBUtil.close(rs,pstmt,conn);
    }
    return list;
}
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service层：

StudentService：

public List<EchartsBean> findCountByAddress();
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StudentServiceImpl：

@Override
public List<EchartsBean> findCountByAddress(){
    return studentDao.findCountByAddress();
}
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servlet:

CountServlet:

package com.jishou.servlet;

import com.alibaba.fastjson.JSONObject;
import com.jishou.pojo.EchartsBean;
import com.jishou.service.StudentService;
import com.jishou.service.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map;

@WebServlet(name = "CountServlet",urlPatterns = "/count")
public class CountServlet extends HttpServlet {

    private StudentService studentService=new StudentServiceImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        List<EchartsBean> list = studentService.findCountByAddress();
        //将List集合转换成json数据
        String json = JSONObject.toJSONString(list);
        req.setAttribute("list",json);
        req.getRequestDispatcher("tubiao.jsp").forward(req,resp);
    }
}
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left.jsp 左边菜单页面添加菜单–统计模块：

注意：超链接的指向

 <a href="count" target="main">区域统计</a>
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<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<div>
    <a href="#" target="main">首页</a>
    <dl>
        <dt>
            学生管理
        </dt>
        <dd>
            <a href="listpage" target="main">学生列表</a>
        </dd>
        <dd>
            <a href="add.jsp" target="main">添加学生</a>
        </dd>
    </dl>
    <dl>
        <dt>
            教师管理
        </dt>
        <dd>
            <a href="listteas" target="main">教师列表</a>
        </dd>
        <dd>
            <a href="" target="main">添加教师</a>
        </dd>
    </dl>
    <dl>
        <dt>
            班级管理
        </dt>
        <dd>
            <a href="" target="main">班级列表</a>
        </dd>
        <dd>
            <a href="" target="main">添加班级</a>
        </dd>
    </dl>
    <dl>
        <dt>
            统计模块
        </dt>
        <dd>
            <a href="count" target="main">区域统计</a>
        </dd>

    </dl>
    <dl>
        <dt>
            系统管理
        </dt>
        <dd>
            <a href="" target="main">修改密码</a>
        </dd>
        <dd>
            <a href="logout" target="_parent">退出系统</a>
        </dd>
    </dl>
</div>
</body>
</html>
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点击区域统计菜单，进入CountServlet，最终效果如下：动态的

在这里插入图片描述

eg18: 连表查询一对一查询所有

数据库设计

设计tea老师表和clazz班级表

tea表字段：

int id 主键自增 varchar tname 教师姓名 int age 年龄

varchar subject 授课科目 int cid 班级id 管理班级表主键

clazz班级表字段：

int id 主键自增 varchar cname 班级名称

实体类

教室和班级一对一关系，写Teacher属性的时候直接把Clazz clazz; 班级对象作为Teacher的属性

Clazz：

package com.jishou.pojo;

public class Clazz {

    private int id;
    private String className;

    public Clazz() {
    }

    public Clazz(int id, String className) {
        this.id = id;
        this.className = className;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getClassName() {
        return className;
    }

    public void setClassName(String className) {
        this.className = className;
    }

    @Override
    public String toString() {
        return "Clazz{" +
                "id=" + id +
                ", className='" + className + '\'' +
                '}';
    }
}
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Teacher：

package com.jishou.pojo;

public class Teacher {
    private int id;
    private String teaName;
    private int age;
    private String subject;
    private Clazz clazz;//一对一 一个老师带一个班级

    public Teacher() {
    }

    public Teacher(int id, String teaName, int age, String subject, Clazz clazz) {
        this.id = id;
        this.teaName = teaName;
        this.age = age;
        this.subject = subject;
        this.clazz = clazz;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTeaName() {
        return teaName;
    }

    public void setTeaName(String teaName) {
        this.teaName = teaName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getSubject() {
        return subject;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    public Clazz getClazz() {
        return clazz;
    }

    public void setClazz(Clazz clazz) {
        this.clazz = clazz;
    }

    @Override
    public String toString() {
        return "Teacher{" +
                "id=" + id +
                ", teaName='" + teaName + '\'' +
                ", age=" + age +
                ", subject='" + subject + '\'' +
                ", clazz=" + clazz +
                '}';
    }
}
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dao层

TeacherDao：

package com.jishou.dao;

import com.jishou.pojo.Teacher;

import java.util.List;

public interface TeacherDao {
    public List<Teacher> queryAllTeachers();
}
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TeacherDaoImpl：

package com.jishou.dao;

import com.jishou.pojo.Clazz;
import com.jishou.pojo.Student;
import com.jishou.pojo.Teacher;
import com.jishou.util.DBUtil;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class TeacherDaoImpl implements TeacherDao {
    @Override
    public List<Teacher> queryAllTeachers() {
        String sql="select t.id,t.tname,t.age,t.subject,c.id,c.cname  FROM tea t ,clazz c where t.id=c.id";

        Connection conn = DBUtil.getConnection();
        List<Teacher> list = new ArrayList<>();
        PreparedStatement pstmt=null;
        ResultSet rs=null;
        try {
            pstmt= conn.prepareStatement(sql);
            rs= pstmt.executeQuery();

            while (rs.next()) {
                int id = rs.getInt(1);
                String tname = rs.getString(2);
                int age = rs.getInt(3);
                String subject = rs.getString(4);
                int cid = rs.getInt(5);
                String cname = rs.getString(6);
                Clazz clazz=new Clazz(cid,cname);
                Teacher teacher=new Teacher(id,tname,age,subject,clazz);
                list.add(teacher);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            DBUtil.close(rs,pstmt,conn);
        }
        return list;
    }
}
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service层

TeacherService：

package com.jishou.service;

import com.jishou.pojo.Teacher;

import java.util.List;

public interface TeacherService {
    public List<Teacher> queryAllTeachers();
}
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TeacherServiceImpl：

package com.jishou.service;

import com.jishou.dao.TeacherDao;
import com.jishou.dao.TeacherDaoImpl;
import com.jishou.pojo.Teacher;

import java.util.List;

public class TeacherServiceImpl implements TeacherService {
    private TeacherDao teacherDao=new TeacherDaoImpl();
    @Override
    public List<Teacher> queryAllTeachers() {
        return teacherDao.queryAllTeachers();
    }
}
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servlet

ListTeasServlet：

package com.jishou.servlet;

import com.jishou.pojo.Teacher;
import com.jishou.service.TeacherService;
import com.jishou.service.TeacherServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet(name = "ListTeasServlet",urlPatterns = "/listteas")
public class ListTeasServlet extends HttpServlet {
    private TeacherService teacherService=new TeacherServiceImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<Teacher> teachers = teacherService.queryAllTeachers();

        req.setAttribute("list",teachers);
        req.getRequestDispatcher("tealist.jsp").forward(req,resp);
    }
}
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前端页面

tealist.jsp：

<%@ page import="java.util.List" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
    <title>Title</title>
</head>

<body>

<center>
<h1>教师管理系统</h1>

<table width="70%" height="50%">
    <tr>
        <td>Id</td>
        <td>姓名</td>
        <td>年龄</td>
        <td>授课科目</td>
        <td>所带班级</td>

    </tr>


        <c:if test="${list ne null and list.size() gt 0}">

            <c:forEach var="t" items="${list}">

                <tr>

                    <td>${t.id}</td>
                    <td>${t.teaName}</td>
                    <td>${t.age}</td>
                    <td>${t.subject}</td>
                    <td>${t.clazz.className}</td>
                </tr>
            </c:forEach>
        </c:if>

</table>
</center>
</body>
</html>
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7.效果点击左边教师列表超链接

在这里插入图片描述

eg19: 实现角色权限管理

角色权限管理

3个概念：

用户：当前登录系统的用户

角色：某个用户具备的角色管理员或者普通会员

权限：所拥有的资源，表现为所能操作的菜单的多少

关系：
用户和角色一对一角色和菜单多对多
一个用户一个角色，一个角色多个权限

不同的用户不同的角色，不同的角色不同的权限；所以每个用户登录之后显示的权限菜单不一样

流程：

用户正常登录进入系统，   由于不同用户不同角色不同的权限大小，登录之后必须权限查询，在列表上展现出来
登录页面--》 login后台-----》登录成功之后 获取roleId----->再根据roleId查询出对应的权限信息
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表的设计：

3张主表 
	user  role   menu ，
2张中间表  user_role   role_menu

主表：
user:   id  username  password
role:   roleid  rolename
menu:   id  name  url  target  pid

中间表：	

user_role：   uid  rid	
role_menu:     rid  mid   
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实体类设计：

3个实体类：
User:

Integer id;

String username;

String password;

Role role;

Role:

Integer roleId;

String roleName

Menu:

int id;

	String name;
	 String url;
	 String target;
	int pid;
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实现流程：

	1.  login.jsp
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```form表单登录到后台login

2. servletlogin登录的后台逻辑实现登录

sql: 3表联查查询出来的user里面会有role信息，包括roleId

再根据roleId查询出对应的权限信息；

吧登录成功的User对象和List

对象放到session中,

跳转到index.jsp中

4. left.jsp 左边菜单列表通过循环遍历显示出来

<ul>

    <c:forEach var="m" items="${menus}">

        <li>
            <a href="${m.url}" target="${m.target}">${m.name}</a>
        </li>
    </c:forEach>

</ul>
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步骤：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<h1>登录页面</h1>

<!--前端访问路径都不加/ -->
<form action="login" method="post">
    用户名： <input type="text" name="username"><br>
    密码： <input type="password" name="password"><br>
    <input type="submit" value="登录">
    <a href="register.jsp">立即注册</a>

</form>

</body>
</html>
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实体类pojo

User:

package com.jishou.pojo;

public class User {

    private int id;
    private String username;
    private String password;
    private Role role;

    public User() {
    }

    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public User(int id, String username, String password, Role role) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.role = role;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Role getRole() {
        return role;
    }

    public void setRole(Role role) {
        this.role = role;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", role=" + role +
                '}';
    }
}
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Role:

package com.jishou.pojo;

public class Role {

    private int roleId;
    private String roleName;

    public Role() {
    }

    public Role(int roleId, String roleName) {
        this.roleId = roleId;
        this.roleName = roleName;
    }

    public int getRoleId() {
        return roleId;
    }

    public void setRoleId(int roleId) {
        this.roleId = roleId;
    }

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

    @Override
    public String toString() {
        return "Role{" +
                "roleId=" + roleId +
                ", roleName='" + roleName + '\'' +
                '}';
    }
}
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Menu:

package com.jishou.pojo;

public class Menu {

    private int id;
    private String name;
    private String url;
    private String target;
    private int pid;

    public Menu() {
    }

    public Menu(int id, String name, String url, String target, int pid) {
        this.id = id;
        this.name = name;
        this.url = url;
        this.target = target;
        this.pid = pid;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getTarget() {
        return target;
    }

    public void setTarget(String target) {
        this.target = target;
    }

    public int getPid() {
        return pid;
    }

    public void setPid(int pid) {
        this.pid = pid;
    }

    @Override
    public String toString() {
        return "Menu{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", url='" + url + '\'' +
                ", target='" + target + '\'' +
                ", pid=" + pid +
                '}';
    }
}
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dao层

UserDao:

package com.jishou.dao;

import com.jishou.pojo.Menu;
import com.jishou.pojo.User;

import java.util.List;

public interface UserDao {

    public User queryOneUser(User user);

    public List<Menu> queryMenusByRoleId(int roleId);
}
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UserDaoImpl:

package com.jishou.dao;

import com.jishou.pojo.Menu;
import com.jishou.pojo.Role;
import com.jishou.pojo.User;
import com.jishou.util.DBUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDaoImpl implements UserDao{
    @Override
    public User queryOneUser(User user) {
        String sql="select u.id,u.username,u.`password` ,r.roleid,r.rolename from user u,user_role ur ,role r where u.id=ur.uid and ur.rid=r.roleid and u.username=? and u.password=?";

        PreparedStatement pstmt=null;
        ResultSet rs=null;
        //2. 获取连接   修路
        Connection conn = DBUtil.getConnection();
        User u=null;
        try {
            //3. 创建PreparedStatement   造车
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1,user.getUsername());
            pstmt.setString(2,user.getPassword());
            //4. 执行sql    拉货
            rs = pstmt.executeQuery();
            //5. 处理结果集 查询会有结果集  处理货物
            if (rs.next()) {
                int id = rs.getInt(1);
                String username = rs.getString(2);
                String password = rs.getString(3);
                int roleid = rs.getInt(4);
                String rolename = rs.getString(5);
                Role role=new Role(roleid,rolename);
                u=new User(id,username,password,role);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            //6. 关闭资源   货 车 路全都毁了
            DBUtil.close(rs,pstmt,conn);
        }

        return u;
    }

    @Override
    public List<Menu> queryMenusByRoleId(int roleId) {
        String sql="select m.* from role_menu rm ,menu m where rm.mid=m.id and rm.rid=?";

        PreparedStatement pstmt=null;
        ResultSet rs=null;
        List<Menu> list=new ArrayList<>();

        //2. 获取连接   修路
        Connection conn = DBUtil.getConnection();
        try {
            //3. 创建PreparedStatement   造车
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1,roleId);
            //4. 执行sql    拉货
            rs = pstmt.executeQuery();
            //5. 处理结果集 查询会有结果集  处理货物
            while (rs.next()) {
                int id = rs.getInt(1);
                String name = rs.getString(2);
                String url = rs.getString(3);
                String target = rs.getString(4);
                int pid = rs.getInt(5);
                Menu menu=new Menu(id,name,url,target,pid);
                list.add(menu);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            //6. 关闭资源   货 车 路全都毁了
            DBUtil.close(rs,pstmt,conn);
        }

        return list;
    }
}
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service层

UserService:

package com.jishou.service;

import com.jishou.pojo.Menu;
import com.jishou.pojo.User;

import java.util.List;

public interface UserService {
    public User queryOneUser(User user);

    public List<Menu> queryMenusByRoleId(int roleId);
}
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UserServiceImpl:

package com.jishou.service;

import com.jishou.dao.UserDao;
import com.jishou.dao.UserDaoImpl;
import com.jishou.pojo.Menu;
import com.jishou.pojo.User;

import java.util.List;

public class UserServiceImpl implements UserService {
    private UserDao userDao=new UserDaoImpl();

    @Override
    public User queryOneUser(User user) {
        return userDao.queryOneUser(user);
    }

    @Override
    public List<Menu> queryMenusByRoleId(int roleId) {
        return userDao.queryMenusByRoleId(roleId);
    }
}
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servlet

LoginServlet:

package com.jishou.servlet;

import com.jishou.dao.UserDao;
import com.jishou.dao.UserDaoImpl;
import com.jishou.pojo.Menu;
import com.jishou.pojo.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.List;

@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {

    private UserDao userDao=new UserDaoImpl();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        User user=new User(username,password);
        User htUser = userDao.queryOneUser(user);
        if(htUser!=null){
            //登录成功
            //再根据roleId来查询权限信息
            int roleId = htUser.getRole().getRoleId();
            List<Menu> menus = userDao.queryMenusByRoleId(roleId);
            //放到session对象中
            HttpSession session = req.getSession();
            session.setAttribute("user",htUser);
            session.setAttribute("menus",menus);
            //跳转到首页
            resp.sendRedirect("index.jsp");

        }else{
            resp.sendRedirect("login.jsp");
        }

    }
}
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前端left.jsp渲染菜单

index.jsp为frameset,3个网页的集合

left.jsp

<%--
  Created by IntelliJ IDEA.
  User: mumusan
  Date: 2021/6/2
  Time: 16:20
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<div>
    <ul>

        <c:forEach var="m" items="${menus}">

            <li>
                <a href="${m.url}" target="${m.target}">${m.name}</a>
            </li>
        </c:forEach>

    </ul>
</div>
</body>
</html>
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访问测试；使用不同的用户访问登录测试

eg20: 使用maven创建工程

下载maven压缩包

apache-maven-3.6.0-bin.zip

解压压缩包，在conf/setting.xml配置阿里云中央仓库

注意：不要解压在中文路径下

在conf/setting.xml配置本地仓库路径和阿里云中央仓库

<localRepository>D:\soft\repository</localRepository>
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 <!-- 阿里云仓库 -->
 <mirror>
     <id>alimaven</id>
     <mirrorOf>central</mirrorOf>
     <name>aliyun maven</name>
     <url>https://maven.aliyun.com/repository/central</url>
 </mirror>
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idea里面关联maven

setting------maven----配置maven home 和 User setting file

New Project Settings—Settings For New Projects…也需要同样配置

在这里插入图片描述

创建maven web工程

new project----maven project

在这里插入图片描述

pom.xml文件里面添加依赖

注意： pom.xml里面自动生成的这些东西可以删除

<name>maven0100 Maven Webapp</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>

<properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <maven.compiler.source>1.7</maven.compiler.source>
  <maven.compiler.target>1.7</maven.compiler.target>
</properties>

<dependencies>
  <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.11</version>
    <scope>test</scope>
  </dependency>
</dependencies>

<build>
  <finalName>maven0100</finalName>
  <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
    <plugins>
      <plugin>
        <artifactId>maven-clean-plugin</artifactId>
        <version>3.1.0</version>
      </plugin>
      <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
      <plugin>
        <artifactId>maven-resources-plugin</artifactId>
        <version>3.0.2</version>
      </plugin>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.0</version>
      </plugin>
      <plugin>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.22.1</version>
      </plugin>
      <plugin>
        <artifactId>maven-war-plugin</artifactId>
        <version>3.2.2</version>
      </plugin>
      <plugin>
        <artifactId>maven-install-plugin</artifactId>
        <version>2.5.2</version>
      </plugin>
      <plugin>
        <artifactId>maven-deploy-plugin</artifactId>
        <version>2.8.2</version>
      </plugin>
    </plugins>
  </pluginManagement>
</build>
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完整的pom文件，添加web依赖后的工程

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.jishou</groupId>
  <artifactId>maven0100</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>

    <!-- JSP -->
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.2</version>
      <scope>provided</scope>
    </dependency>

    <!-- JSTL -->
    <dependency>
      <groupId>jstl</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>


  </dependencies>
  <build>
    <pluginManagement>
      <plugins>
        <!-- 配置Tomcat插件 -->
        <plugin>
          <groupId>org.apache.tomcat.maven</groupId>
          <artifactId>tomcat7-maven-plugin</artifactId>
          <version>2.2</version>
          <configuration>
            <port>8082</port>
            <path>/</path>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>

</project>
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依赖添加完毕后记得更新maven依赖

右边菜单 maven -------左上方刷新图标点击

编写代码

src/main/java

底下创建一个Servlet

package com.jihsou.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "HelloServlet",urlPatterns = "/hello")
public class HelloServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.sendRedirect("index.jsp");
    }
}
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index.jsp

内容为hello worldd

启动运行tomcat服务器 :

这里使用maven-tomcat插件

右面M 图标点击输入 tomcat7:run 即可启动

浏览器访问：http://localhost:8082/hello

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6.编写service层接口和实现类

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