我们在用Mybatis开发时会遇到类似于对象内包含对象属性的情况，我们编辑班级时需要将本班教师封装为List一并返回，诸如类似情况我们可以使用collection进行分表操作

现有表如下:

1.创建实体类

//Class.java
package com.demo.domain;import java.util.List;public class Class {private Long id;private String className;private List<Teacher> teacherList;public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getClassName() {return className;}public void setClassName(String className) {this.className = className;}public List<Teacher> getTeacherList() {return teacherList;}public void setTeacherList(List<Teacher> teacherList) {this.teacherList = teacherList;}
}

//Teacher.java
package com.demo.domain;public class Teacher {private Long id;private String name;private String sex;public Long getId() {return id;}public void setId(Long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}
}

2.编辑接口

//ClassService.java
package com.demo.service;import java.util.List;
import com.demo.domain.Class;
public interface ClassService {List<Class> listAll();
}//ClassServiceImp.java
package com.demo.service.imp;import com.demo.domain.Class;
import com.demo.mapper.ClassMapper;
import com.demo.service.ClassService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.List;
@Service
public class ClassServiceImp implements ClassService {@Autowiredprivate ClassMapper classMapper;@Overridepublic List<Class> listAll() {return classMapper.listAll();}
}//ClassMapper.java
package com.demo.mapper;import com.demo.domain.Class;
import org.apache.ibatis.annotations.Mapper;import java.util.List;@Mapper
public interface ClassMapper {List<Class> listAll();
}

  ClassMapper.xml 

<?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.demo.mapper.ClassMapper"><resultMap id="BaseResultMap" type="com.demo.domain.Class"><id column="id" jdbcType="BIGINT" property="id"/><result column="class_name" jdbcType="VARCHAR" property="className"/><collection property="teacherList" select="getTeacherListByClassId" column="id" javaType="ArrayList"></collection></resultMap><select id="listAll" resultMap="BaseResultMap" parameterType="int">select *from class;</select><select id="getTeacherListByClassId" parameterType="int" resultType="com.demo.domain.Teacher">select t.*from teacher t,ref_class_teacher rwhere t.id = r.class_idand t.id = #{id};</select>
</mapper>

3.测试接口

[{"id": 1,"className": "一班","teacherList": [{"id": 1,"name": "赵老师","sex": "男"},{"id": 1,"name": "赵老师","sex": "男"},{"id": 1,"name": "赵老师","sex": "男"}]},{"id": 2,"className": "二班","teacherList": [{"id": 2,"name": "钱老师","sex": "女"},{"id": 2,"name": "钱老师","sex": "女"}]},{"id": 3,"className": "三班","teacherList": [{"id": 3,"name": "孙老师","sex": "男"},{"id": 3,"name": "孙老师","sex": "男"},{"id": 3,"name": "孙老师","sex": "男"}]}
]