Mybatis结果集映射(一) 对象嵌套对象

   如果mybatis查询返回的对象中里面还嵌套着其它对象，那么就需要结果集映射。
   例如我们要从数据库表中查询ExportOperationsVo的id, operationTime, 和。

实体类：

public class ExportOperationsVo {
	private String id;
	private ExportUserVo operator;  //嵌套ExportUserVo对象
	private Date operationTime;
    private ExportUserVo receiver;  //嵌套ExportUserVo对象
    }
public class ExportUserVo {
	private String userId;
	private String username;
	private String departmentId;
	private String departmentName;
	}

dao层接口：

 public ExportOperationsVo getExportOperationsVoById(@Param("id") String id);

XML:

<select id="getExportOperationsVoById"
		resultMap="ExportOperationMap">
		select
		id,
		src_operator_id,
		des_operator_id,
		operation_time,
		from operation_table
		where id=#{id}
	</select>
	<resultMap id="ExportOperationMap"
		type="ExportOperationsVo的全限定类名">
		<result column="id" property="id" />
		<!--operation_time为数据库表字段，对应ExportOperationsVo的operationTime属性-->
		<result column="operation_time" property="operationTime" />
		<association property="receiver"
			javaType="ExportUserVo全限定类名">
			<result column="des_operator_id" property="userId" />
		</association>
		<!--des_operator_id为数据库表字段，对应receiver的userId属性-->
		<association property="operator"
			javaType="ExportUserVo全限定类名">
			<result column="src_operator_id" property="userId" />
		</association>
	</resultMap>

注意resultMap中要按照 的顺序写，不然会报错