20、Mybatis进阶：返回map对象的helloworld

本文内容来自上硅谷

1返回的结果集为一条时返回map对象

1.1xml配置如下

resultType为map

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

1.2dao

	//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);

1.3Junit

	@Test
	public void test04() throws IOException{
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			Map<String, Object> map = mapper.getEmpByIdReturnMap(1);
			System.out.println(map);
		}finally{
			openSession.close();
		}
	}

1.4效果

2如果返回多条记录要封装在map中

2.1xml

返回类为employee

 	<!--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>

2.2dao

@MapKey:告诉mybatis封装这个map的时候使用哪个属性作为map的key

	//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("lastName")
	public Map<String, Employee> getEmpByLastNameLikeReturnMap(String lastName);

2.3Junit

	
	@Test
	public void test04() throws IOException{
		
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try{
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			Map<String, Employee> map = mapper.getEmpByLastNameLikeReturnMap("%r%");
			System.out.println(map);
		}finally{
			openSession.close();
		}
	}

2.4效果

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