• 场景
  当我们需要查询一个班集里所有学生信息时，需要用到一对多的查询，此时使用Mybatis的collection属性处理。

• 实例
  ClassInfo.java

public class ClassInfo {

  private String className;
  private String classCode;
  private String chargeMan;
  private List<Student> students;

  public void setClassName (String className) {
    this.className = className;
  }
  public String getClassName () {
    return this.className;
  }
  
  ... ...
}

Student.java

public class Student {

  private String name;
  private int age;
  private String sex;
  private String classCode;

  public void setName (String name) {
    this.name = name;
  }

  public String getName () {
    return this.name;
  }

  ... ...
}

ClassInfoMapper.java

public interface ClassInfoMapper {
  ClassInfo getClassAndStudentInfoByClassCode (String classCode);
}

ClassInfoMapper.xml

<select id="getClassAndStudentInfoByClassCode" resultMap="classAndStudentMap">
  SELET class_name, c.class_code, name, class_charge, s.class_code, age, sex
  FROM class AS c LEFT JOIN student AS s ON c.class_code = s.class_code
  WHERE c.class_code = #{class_code} 
</select>

<resultMap id="classAndStudentMap" type="com.cat.pojo.ClassInfo">
  <result column="class_code" property="classCode" />
  <result column="class_name" property="className" />
  <result column="charge_man" property="chargeMan" />

  <collection property="students" ofType="com.cat.pojo.Student">
    <result column="name" property="name"/>
    <result column="age" property="age" />
    <result column="sex" property="sex" />
  </collection>
</resultMap>

通过以上的配制便可实现样合查询的集合属性封装。