Mybatis查询结果集返回信息使用大Map进行封装实现不用POJO类的映射并达到对应取值的效果-----Mybatis框架

发布于：2023-09-21 ⋅ 阅读:(77) ⋅ 点赞:(0) 
package com.powernode.mybatis.mappers;

import com.powernode.mybatis.POJO.Car;
import org.apache.ibatis.annotations.MapKey;

import java.util.List;
import java.util.Map;

public interface CarMapper
{
    //查询所有Car,返回一个Map集合
    //map集合的Key是主键值,map值是Car对象
    @MapKey("id")
    Map<Long,Map<String,Object>> selectMap();
    List<Map<String,Object>> selectAllCar();
    Map<String,Object> selectByIdGetMap(Long id);
    List<Car> selectByCarId(Long id);
    //模糊查询的对象可能有多个,会出问题吗?
    Car selectByBrand(String brand);
    List<Car> selectAll();
    Car selectById(Long id);
}

package com.powernode.mybatis.mappers;

import com.powernode.mybatis.POJO.Car;
import org.apache.ibatis.annotations.MapKey;

import java.util.List;
import java.util.Map;

public interface CarMapper
{
    //查询所有Car,返回一个Map集合
    //map集合的Key是主键值,map值是Car对象
    @MapKey("id")
    Map<Long,Map<String,Object>> selectMap();
    List<Map<String,Object>> selectAllCar();
    Map<String,Object> selectByIdGetMap(Long id);
    List<Car> selectByCarId(Long id);
    //模糊查询的对象可能有多个,会出问题吗?
    Car selectByBrand(String brand);
    List<Car> selectAll();
    Car selectById(Long id);
}

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

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.powernode.mybatis.mappers.CarMapper">
    <select id="selectById" resultType="Car">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id};
    </select>
    <select id="selectAll" resultType="Car">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
    </select>
    <select id="selectByBrand" resultType="Car">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            brand like '%${brand}%';
    </select>
    <select id="selectByCarId" resultType="Car">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id};
    </select>
<!--    查询结果没有合适的接收对象,没有合适的POJO类-->
    <select id="selectByIdGetMap" resultType="java.util.Map">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id};
    </select>
    <select id="selectAllCar" resultType="Map">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
    </select>
    <select id="selectMap" resultType="Map">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
    </select>
</mapper>
<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.powernode.mybatis.mappers.CarMapper">
    <select id="selectById" resultType="Car">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id};
    </select>
    <select id="selectAll" resultType="Car">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
    </select>
    <select id="selectByBrand" resultType="Car">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            brand like '%${brand}%';
    </select>
    <select id="selectByCarId" resultType="Car">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id};
    </select>
<!--    查询结果没有合适的接收对象,没有合适的POJO类-->
    <select id="selectByIdGetMap" resultType="java.util.Map">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
        where
            id = #{id};
    </select>
    <select id="selectAllCar" resultType="Map">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
    </select>
    <select id="selectMap" resultType="Map">
        select
            id as id,
            car_num as carNum,
            brand as brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
        from
            t_car
    </select>
</mapper>
package com.powernode.mybatis.Test;

import com.powernode.mybatis.POJO.Car;
import com.powernode.mybatis.mappers.CarMapper;
import com.powernode.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;

import java.util.List;
import java.util.Map;

public class Test
{
    @org.junit.Test
    public void TestPojoSelect()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        Car car = mapper.selectById(5l);
        System.out.println(car);
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestSelectAll()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        List<Car> carList = mapper.selectAll();
        carList.forEach(car -> {
            System.out.println(car);
        });
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestBrand()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        //会报错,因为返回了多条记录了
        Car car = mapper.selectByBrand("比亚迪");
        System.out.println(car);
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestSelectByCarId()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        List<Car> carList = mapper.selectByCarId(5L);
        carList.forEach(car -> {
            System.out.println(car);
        });
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestSelectByIdGetMap()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        Map<String, Object> car = mapper.selectByIdGetMap(5l);
        System.out.println(car);
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestselectAllCar()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        List<Map<String, Object>> maps = mapper.selectAllCar();
        maps.forEach(map ->{
            System.out.println(map);
        });
    }
    @org.junit.Test
    public void TestMap()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        Map<Long, Map<String, Object>> longMapMap = mapper.selectMap();
        System.out.println(longMapMap);
        Map<String, Object> map = longMapMap.get(3L);
        System.out.println(map);
    }
}

package com.powernode.mybatis.Test;

import com.powernode.mybatis.POJO.Car;
import com.powernode.mybatis.mappers.CarMapper;
import com.powernode.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;

import java.util.List;
import java.util.Map;

public class Test
{
    @org.junit.Test
    public void TestPojoSelect()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        Car car = mapper.selectById(5l);
        System.out.println(car);
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestSelectAll()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        List<Car> carList = mapper.selectAll();
        carList.forEach(car -> {
            System.out.println(car);
        });
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestBrand()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        //会报错,因为返回了多条记录了
        Car car = mapper.selectByBrand("比亚迪");
        System.out.println(car);
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestSelectByCarId()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        List<Car> carList = mapper.selectByCarId(5L);
        carList.forEach(car -> {
            System.out.println(car);
        });
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestSelectByIdGetMap()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        Map<String, Object> car = mapper.selectByIdGetMap(5l);
        System.out.println(car);
        SqlSessionUtil.close(sqlSession);
    }
    @org.junit.Test
    public void TestselectAllCar()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        List<Map<String, Object>> maps = mapper.selectAllCar();
        maps.forEach(map ->{
            System.out.println(map);
        });
    }
    @org.junit.Test
    public void TestMap()
    {
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        Map<Long, Map<String, Object>> longMapMap = mapper.selectMap();
        System.out.println(longMapMap);
        Map<String, Object> map = longMapMap.get(3L);
        System.out.println(map);
    }
}

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