collection和association的使用区别

一对一使用association

一对多使用ollection

 

 

班级实体类

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public class Clazz implements Serializable {       private Integer id;     private String name;   }

　　

学生实体类

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public class Student implements Serializable {       private Integer id;     private String name;     private Integer age;     private Integer classId;   }

　　

学生对班级，一对一关系

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public class ClazzAndStudentVO implements Serializable {       private Integer id;     private String name;     private Integer age;     private Integer classId;     private Clazz clazz;   }

　　

学生对班级，一对一映射关系

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<mapper namespace="xx.xx.xx.xx.StudentAndClazzMapper">         <resultMap id="StudentAndClazzVOMap"         type="cn.tedu.mybatis.vo.StudentAndClazzVO">         <!-- id节点：主键的配置 -->         <!-- column：查询结果的列名 -->         <!-- property：数据类型的属性名 -->         <id column="id" property="id"/>             <result column="name" property="name"/>             <result column="age" property="age"/>             <result column="class_id" property="class_id"/>         <association property="clazz" column="department_sn" javaType="Clazz" >             <id property="id" column="cid" />             <result property="name" column="cname" javaType="String"/>         </association>     </resultMap>

　　

班级对学生一对多关系

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public class StudentAndClazzVO implements Serializable {       private Integer clazzId;     private String clazzName;     private List<Student> students; }

　　

班级对学生一对多，映射关系

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<mapper namespace="xx.xx.xx.xx.StudentAndClazzMapper">     <resultMap id="StudentAndClazzVOMap"         type="cn.tedu.mybatis.vo.StudentAndClazzVO">         <!-- id节点：主键的配置 -->         <!-- column：查询结果的列名 -->         <!-- property：数据类型的属性名 -->         <id column="clazz_id" property="clazzId"/>         <!-- 其它结果的配置 -->         <result column="clazz_name" property="clazzName"/>         <!-- 配置List集合 -->         <!-- ofType：集合中放的哪种类型的数据 -->         <collection property="students"             ofType="xx.xx.xx.Student">               <id column="id" property="id"/>             <result column="name" property="name"/>             <result column="age" property="age"/>             <result column="class_id" property="class_id"/>         </collection>     </resultMap>