Mybatis-Plus处理Mysql Json类型字段_mybatis plus mysql json

概要

Mysql 5.7.8开始支持Json对象和Json数组，但在Mysql 8版本中使用Json性能更佳。

使用Json格式的好处：

1. 无须预定义字段：字段可以无限拓展，避免了ALTER ADD COLUMN的操作，使用更加灵活。
2. 处理稀疏字段：避免了稀疏字段的NULL值，避免冗余存储。
3. 支持索引：相比于字符串格式的JSON，JSON类型支持索引做特定的查询优化。

整体实现流程

1. 查看Mysql版本

SELECT VERSION();
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2、创建mysql表

CREATE TABLE `test` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `text` json DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4;
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3、定义实体类

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.extension.handlers.FastjsonTypeHandler;
import lombok.Data;

@Data
//开启自动映射
@TableName(value = "test",autoResultMap = true)
public class Test {

    @TableId(type = IdType.AUTO)
    private Integer id;
	//定义Json字段handler
    @TableField(typeHandler = FastjsonTypeHandler.class)
    private JsonNode text;
}
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import lombok.Data;

import java.io.Serializable;

@Data
public class JsonNode implements Serializable {

    private Integer id;

    private String name;

    private Integer age;
}
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4、定义Mapper、Service、ServiceImpl

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.yiyou.base.entity.Test;

public interface TestMapper extends BaseMapper<Test> {
}
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import com.baomidou.mybatisplus.extension.service.IService;
import com.yiyou.base.entity.Test;

public interface TestService extends IService<Test> {

    boolean insert(Test test);
}
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import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.yiyou.base.entity.Test;
import com.yiyou.base.mapper.TestMapper;
import com.yiyou.base.service.TestService;
import org.springframework.stereotype.Service;

@Service
public class TestServiceImpl extends ServiceImpl<TestMapper, Test> implements TestService {


    @Override
   public boolean insert(Test test) {
        return this.saveOrUpdate(test);
    }
}
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5、Controller层实现

import com.baomidou.mybatisplus.extension.conditions.query.LambdaQueryChainWrapper;
import com.yiyou.base.entity.Test;
import com.yiyou.base.service.TestService;
import com.yiyou.model.R;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.Objects;


@Slf4j
@Api(tags = "test")
@RestController
@RequestMapping("/test")
public class TestController {

    @Autowired
    private TestService testService;

    @ApiOperation("新增")
    @PostMapping("/save")
    public R<Boolean> save(@RequestBody Test test) {
        return R.ok(testService.insert(test));
    }

    @ApiOperation("根据Id获取对象")
    @GetMapping("/getById/{id}")
    public R<Test> getById(@PathVariable("id") Integer id) {
        return R.ok(testService.getById(id));
    }

    @ApiOperation("根据Id删除")
    @DeleteMapping("/deleteById/{id}")
    public R<Boolean> deleteById(@PathVariable("id") Integer id) {
        return R.ok(testService.removeById(id));
    }

    @ApiOperation("条件查询")
    @PostMapping("/findList")
    public R<List<Test>> findList(@RequestBody Test test) {
        LambdaQueryChainWrapper<Test> queryWrapper =  testService.lambdaQuery();
        queryWrapper
                .eq(Objects.nonNull(test.getId()),Test::getId,test.getId())
//                .apply(Objects.nonNull(test.getText()),"text -> '$.name' LIKE CONCAT('%',{0},'%')",test.getText().getName())
                .apply(Objects.nonNull(test.getText()), "text -> '$.age' = {0}", test.getText().getAge());
//                .like(Objects.nonNull(test.getText()),Test::getText,test.getText());
        return R.ok(queryWrapper.list());
    }
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技术细节

• Json字段模糊查询

SELECT * FROM TEST WHERE text -> '$[*].name' like '%测%'
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或 上面的"*"也可以使用下标

SELECT * FROM TEST WHERE text -> '$[1].name' like '%测%'
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• Json字段精确查询

• 使用箭头函数

SELECT * FROM TEST WHERE text -> '$.name' = '测试'
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• 使用 JSON_CONTAINS

SELECT * FROM TEST WHERE JSON_CONTAINS(text,JSON_OBJECT('name', '测试'))
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• 查询json中的name字段

SELECT id, text -> '$[*].name' AS name FROM TEST;

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• 使用JSON_EXTRACT 函数,带双引号

SELECT id, JSON_EXTRACT( text, '$[*].name' ) AS name FROM TEST;

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• 使用 JSON_UNQUOTE 函数，不带双引号

SELECT id, JSON_UNQUOTE(text, '$[*].name' ) AS name FROM TEST;

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• 查询Json字段中所有的值，用 “*”

SELECT id, text -> '$[*].*' AS name FROM TEST;

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Mybatis Plus使用LambdaQueryChainWrapper查询

提示：使用apply方法拼接sql片段，apply 是可以通过占位符的形式，传入多个参数。

例如：

LambdaQueryChainWrapper<Test> queryWrapper =  testService.lambdaQuery();
        queryWrapper
.apply(Objects.nonNull(test.getText()),"text -> '$.name' LIKE CONCAT('%',{0},'%')",test.getText().getName())//模糊查询
.apply(Objects.nonNull(test.getText()), "text -> '$.age' = {0}", test.getText().getAge());//精确查询
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