mybatis的mapper映射文件中where,if,foreach等的使用

Posted 2020-09-25

<?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">

<!-- namespace：命名空间，用于隔离sql，还有一个很重要的作用，后面会讲 -->
<mapper namespace="com.it.mapper.UserMapper">
    <sql id="selectUser">
        SELECT * FROM `user`
    </sql>
    
    <!-- 根据多个ID查用户信息 -->
    <select id="selectUsersByIds" parameterType="com.it.entity.QueryVo" resultType="com.it.entity.User">
        <include refid="selectUser"/>
        <where>
            <foreach collection="idsList" item="id" separator="," open="id in (" close=")">
                #{id}
            </foreach>
        </where>
    </select>
</mapper>

UserMapper的映射文件

package com.it.mapper;

import java.util.List;

import com.it.entity.QueryVo;
import com.it.entity.User;

public interface UserMapper {

    
    public User queryUserById(Integer id);
    
    public List<User> findUserByQueryVo(QueryVo vo);
    
    //根据多个id查询用户信息
    public List<User> selectUsersByIds(QueryVo vo);
}

Usermapper接口

package com.it.test;


import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import com.it.entity.QueryVo;
import com.it.entity.User;
import com.it.mapper.UserMapper;

public class MapperTest {
    
    @Test
    public void  testfindUsersByIds() throws Exception{
        //加载配置文件
        String resource = "SqlMapConfig.xml";
        InputStream in = Resources.getResourceAsStream(resource);
        //创建sessionFactory
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(in);
        //创建sqlSession
        SqlSession sqlSession = sessionFactory.openSession();
        
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        
        List<Integer> ids = new ArrayList<Integer>();
        ids.add(10);
        ids.add(16);
        ids.add(22);
        QueryVo vo = new QueryVo();
        vo.setIdsList(ids);
        List<User> users = userMapper.selectUsersByIds(vo);
        for (User user : users) {
            System.out.println(user);
        }
    }
}

测试方法testfindUsersByIds