iBATIS 多对多

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE sqlMap PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"   "http://ibatis.apache.org/dtd/sql-map-2.dtd">
<sqlMap namespace="teacher">
       <typeAlias alias="Teacher" type="com.lsm.domain.Teacher" />
       <typeAlias alias="Student" type="com.lsm.domain.Student" />
  
       <resultMap class="Teacher" id="teacherBasicResultMap">
              <result property="id" column="id"/>
              <result property="name" column="name"/>
              <result property="subject" column="subject"/>
       </resultMap>
       <!-- 下面这个resultMap中有个students属性，这个结果映射继承自上面的结果映射由于有了继承，结果映射可以任意扩展-->
       <resultMap class="Teacher" id="teacherWithTeacherResultMap" extends="teacherBasicResultMap">
              <result property="students" column="id" select="getStudentsByTeacherId"/>
       </resultMap>
       <!-- 这个查询中使用到了上面定义的结果映射，从而决定了查询出来的Teacher中关联出相关的students，在student.xml中配置相似，不再注释。-->
       <select id="getTeachers" resultMap="teacherWithTeacherResultMap">
              <!--[CDATA[  select * from teacher  ]]-->
       </select>
  
       <select id="getStudentsByTeacherId" resultClass="Student">
              <!--[CDATA[   select s.* from student s,student_teacher st where s.id=st.studentid and st.teacherid=#value#   ]]-->
       </select>
</sqlMap>

 

package com.lsm.domain;
import java.util.List;
public class Teacher {
      private int id;
      private String name;
      private String subject;
      private List students; //注意这里有个List类型的students，表示一个老师对应多个学生
 
      public List getStudents() {
            return students;
      }
      public void setStudents(List students) {
            this.students = students;
      }
      //省略掉其他的getter and setter
}

 这里将查询teacher和student的<select>混合在一个文件中了，不如分开清晰。《iBatis2学习笔记：多对多映射(双向) 》中的例子比较好。