mybatis扩展ResultMap

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我们可以从一个<resultMap>中扩展出一个新的<resultMap>,这样原先<resultMap>属性就可以继承过来了。

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<resultMap type="Student" id="StudentResult">     <id property="studId" column="stud_id" />     <result property="name" column="name" />     <result property="email" column="email" />     <result property="phone" column="phone" /> </resultMap> <resultMap type="Student" id="StudentWithAddressResult" extends="StudentResult">     <result property="address.addrId" column="addr_id" />     <result property="address.street" column="street" />     <result property="address.city" column="city" />     <result property="address.state" column="state" />     <result property="address.zip" column="zip" />     <result property="address.country" column="country" /> </resultMap>

这样id为StudentResult的<resultMap>就扩展了id为StudentResult的<resultMap>

如果你指向映射student表中的内容，你可以使用id为StudentResult的<resultMap>

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<select id="findStudentById" parameterType="int" resultMap="StudentResult">     SELECT * FROM STUDENTS WHERE STUD_ID=#{studId} </select>

如果你想要映射Student和Address表中的数据，你可以使用id为StudentWithAddressResult的<resultMap>

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<select id="selectStudentWithAddress" parameterType="int" resultMap="StudentWithAddressResult">     SELECT STUD_ID, NAME, EMAIL, PHONE, A.ADDR_ID, STREET, CITY,     STATE, ZIP, COUNTRY     FROM STUDENTS S LEFT OUTER JOIN ADDRESSES A ON     S.ADDR_ID=A.ADDR_ID     WHERE STUD_ID=#{studId} </select>