MyBatis的collection和association的使用解读

CREATE TABLE `test_school` (
  `id` varchar(20) NOT NULL,
  `name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
 
CREATE TABLE `test_class` (
  `id` varchar(20) NOT NULL,
  `name` varchar(255) DEFAULT NULL,
  `school_id` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
CREATE TABLE `test_teacher` (
  `id` varchar(20) NOT NULL,
  `name` varchar(255) DEFAULT NULL,
  `class_id` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

<?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.boot.security.server.dao.SchoolDao">
 
	<resultMap id="SchoolMap" type="com.boot.security.server.model.TestSchool">
		<id column="id" property="id" />
		<result column="name" property="name" />
		<collection property="testClasses" columnPrefix="tc_"
					resultMap="com.boot.security.server.dao.ClassDao.ClassMap"/>
	</resultMap>
 
	<select id="list" resultMap="SchoolMap">
		select ts.id,ts.name,
			tc.id AS tc_id,
			tc.name AS tc_name,
			tc.school_id AS tc_school_id,
			tt.id AS tc_tt_id,
			tt.name AS tc_tt_name,
			tt.class_id AS tc_tt_class_id
		from test_school ts
		left join test_class tc on ts.id=tc.school_id
		left join test_teacher tt on tc.id=tt.class_id
	</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.boot.security.server.dao.ClassDao">
 
	<resultMap id="ClassMap" type="com.boot.security.server.model.TestClass">
		<id column="id" property="id" />
		<result column="name" property="name" />
		<result column="school_id" property="schoolId" />
		<association property="testTeacher" columnPrefix="tt_"
					 resultMap="com.boot.security.server.dao.TeacherDao.TeacherMap"/>
	</resultMap>
 
</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.boot.security.server.dao.TeacherDao">
 
	<resultMap id="TeacherMap" type="com.boot.security.server.model.TestTeacher">
		<id column="id" property="id" />
		<result column="name" property="name" />
		<result column="class_id" property="classId" />
	</resultMap>
 
</mapper>