Druid数据库连接池【阿里巴巴提供，较为重要】_阿里数据库连接池druid依赖包步骤

Druid连接池使用步骤

1.导包
①druid.jar ②mysql包 （ mysql-connector.jar）
也可以使用maven导入依赖坐标

 <!--druid包-->
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.1.9</version>
    </dependency>
    <!--数据库包-->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.8</version>
    </dependency>
    <!--测试包-->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
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2.配置properties文件
XXX.properties

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/demo6
username=root
password=123456
#初始化连接数量
initialSize=5
#最大连接数
maxActive=10
#最大等待时间
maxWait=30
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[注意：名称可以任意名称、放任意目录，所以不会自动加载，需要手动加载，不同于c3p0]

3.加载XXX.properties配置文件

Properties properties = new Properties();
//JTest是使用Properties对象的类名。即当前类名称
properties.load(JTest.class.getClassLoader().getResourceAsStream("jdbc.properties"));
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4.获取数据库连接池对象
【DruidDataSourceFactory工厂类来获取，参数是properties对象。连接池只有一个，但是池子中可以有多个连接对象】

DataSource dataSource = DruidDataSourceFactory.createDataSource(properties);
        
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5.获取连接

Connection connection = dataSource.getConnection();
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6接下来就是正常的获取Statement【PrepareStatement】对象并操作数据库

connection.prepareStatement()
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7.最后要关闭连接【resultSet、prepareStatement、connection】

示例代码

Flower.java

public class Flower {
    private int id;
    private String name;
    private Double price;
    ……
    ……
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测试类

import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.junit.Test;

import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Properties;

public class JTest {
@Test
    public void df() throws Exception {
    Flower f;
    ArrayList<Flower> flowers = new ArrayList<>();
    Properties properties = new Properties();
    try {
    //读取配置文件
        properties.load(JTest.class.getClassLoader().getResourceAsStream("jdbc.properties"));
        //获得数据库连接池对象
        DataSource dataSource = DruidDataSourceFactory.createDataSource(properties);
        //建立连接
        Connection connection = dataSource.getConnection();
        //为了方便使用statement对象
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery("select * from flower");
        while (resultSet.next()){
            flowers.add(new Flower(resultSet.getInt("id"),
                    resultSet.getString("name"),
                    resultSet.getDouble("price")));

        }
        for (Flower fl:flowers
        ) {
            System.out.println(fl.getName());
            System.out.println(fl.getPrice());
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

}
}
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数据库

示例结果

牡丹
32.2
月季
33.3
玫瑰
45.0

基于druid封装工具类JDBCUtils.java

注意配置文件的名称

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

/*
Druid连接池的工具类
 */
public class JDBCUtils {
    //1.定义成员变量 DataSource
    private static DataSource ds;
    static {
        //1.加载配置文件
        Properties pro = new Properties();
        try {
            pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
            //获取DataSource
            ds = DruidDataSourceFactory.createDataSource(pro);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //获取连接
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
    //释放资源
    public static void close(Statement stmt,Connection conn){
        if (stmt!=null) {
            try {
                stmt.close();
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }
        if (conn!=null){
            try {
                conn.close();//归还连接
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }
    }
    public static void close(ResultSet rs, Statement stmt, Connection conn){
        if (rs!=null) {
            try {
                rs.close();
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }
        if (stmt!=null) {
            try {
                stmt.close();
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }
        if (conn!=null){
            try {
                conn.close();//归还连接
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }
    }
    //获取连接池
    public static DataSource getDataSource(){
        return ds;
    }
}

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测试jdbcUtist.java工具类

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

//测试工具类
public class DruidTest {
    public static void main(String[] args) throws SQLException {
        //给dept表添加一条记录
        //1.获取连接
        Connection conn = JDBCUtils.getConnection();
        //2.定义sql
        String sql = "insert into dept values(?,?,?)";
        //3.获取邮差对象
        PreparedStatement ps = conn.prepareStatement(sql);
        //4.给？赋值
        ps.setInt(1,50);
        ps.setString(2,"HAHAHAH");
        ps.setString(3,"CHINA");
        //5.执行sql
        ps.executeUpdate();
        JDBCUtils.close(ps,conn);
        
    }
}


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工具类借鉴：https://blog.csdn.net/qq_42727102/article/details/102526698