Mybatis xml中配置一对一关系association&一对多关系collection

﹏ヽ暗。殇╰゛Y 2022-05-16 07:07 294阅读 0赞

# Mybatis xml中配置一对一关系association&一对多关系collection #

今天在配置一对一关系映射以及一对多关系映射的时候，把collection中应该使用的ofType配置成了javaType。并且没有及时发现错误，浪费了很多时间去查找此配置问题，特此记一笔。

<resultMap id="DeviceMap" type="com.model.iotr.DeviceDto">
    	<id property="id" column="id"/>
    	<result property="name" column="name"/>
    	<result property="sn" column="sn"/>
    	 
    	<association property="deviceType" javaType="com.model.iot.DeviceTypeDto" columnPrefix="type_">
    		<id property="id" column="id"/>
    		<result property="name" column="name"/>
    		
    		<collection property="typeExts" ofType="com.model.iot.DeviceTypeExtDto" columnPrefix="ext_">
    			<id property="id" column="id"/>
    			<result property="attribute" column="attribute"/>
    			<result property="dataType" column="dataType"/>
    			<result property="unit" column="unit"/>
    		</collection>
    	</association>
    </resultMap>
       <select id="deviceList" resultMap="DeviceMap">
    	SELECT
    		d.id,
    		d.NAME,
    		d.sn,
    		dt.id AS "type_id",
    		dt.name AS "type_name",
    		dte.id AS "type_ext_id",
    		dte.attribute AS "type_ext_attribute",
    		dte.dataType AS "type_ext_dataType",
    		dte.unit AS "type_ext_unit"
    	FROM
    		t_device d
    		LEFT JOIN t_device_type dt ON d.typeId = dt.id
    		LEFT JOIN t_device_type_ext dte ON dt.id = dte.typeId
    </select>

@Data
    public class DeviceDto { 
        private Long id;
        private String name;
        private String sn;
        private DeviceTypeDto deviceType;
    }
    
    @Data
    public class DeviceTypeDto { 
        private Long id;
        private String name;
        private List<DeviceTypeExtDto> typeExts;
    }
    
    @Data
    public class DeviceTypeExtDto { 
        private Long id;
        private String attribute;
        private String dataType;
        private String unit;
    }

**一对一关系中association 使用的是 javaType**  
：：对象对应对象  
**一对多关系中collection 使用的是ofType**  
：：对象对应集合中的对象

**注意columnPrefix的使用方法**