Mybatis系列六：映射文件-结果集封装

「爱情、让人受尽委屈。」 2022-04-24 08:38 344阅读 0赞

一、返回List

public List<Employee> getEmpsByLastNameLike(String lastName);

<select id="getEmpsByLastNameLike" resultType="com.atguigu.mybatis.bean.Employee">
    		select * from tbl_employee where last_name like #{lastName}
    	</select>

二、返回Map  
1、Map<String, Object>

//返回一条记录的map；key就是列名，值就是对应的值
    	public Map<String, Object> getEmpByIdReturnMap(Integer id);

<select id="getEmpByIdReturnMap" resultType="map">
     		select * from tbl_employee where id=#{id}
     	</select>

2、Map<Integer,Employee>

//多条记录封装一个map：Map<Integer,Employee>:键是这条记录的主键，值是记录封装后的javaBean
    	//@MapKey:告诉mybatis封装这个map的时候使用哪个属性作为map的key
    	@MapKey("id")
    	public Map<Integer, Employee> getEmpByLastNameLikeReturnMap(String lastName);

<select id="getEmpByLastNameLikeReturnMap" resultType="com.atguigu.mybatis.bean.Employee">
     		select * from tbl_employee where last_name like #{lastName}
     	</select>

三、测试

@Test
    	public void test() throws IOException{
    		String resource = "mybatis-config.xml";
    		InputStream inputStream = Resources.getResourceAsStream(resource);
    		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    		//1、获取到的SqlSession不会自动提交数据
    		SqlSession openSession = sqlSessionFactory.openSession();
    		try{
    			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
    			
    			//List<Employee>
    			List<Employee> like = mapper.getEmpsByLastNameLike("%e%");
    			for (Employee employee : like) {
    				System.out.println(employee);
    			}
    
    			//Map<String, Object>
    			Map<String, Object> map = mapper.getEmpByIdReturnMap(1);
    			System.out.println(map);
    
    			//Map<Integer, Employee>
    			Map<Integer, Employee> map1 = mapper.getEmpByLastNameLikeReturnMap("%e%");
    			System.out.println(map1);
    
    		}finally{
    			openSession.close();
    		}
    	}

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