mybatis resultMap和转义符 知识点

1.mapper时，resultMap与resultType不能写错.Map为自定义属性，没写的属性就不映射，可以把一对一的级连关系值也可以映射上

<mapper namespace="com.qbd.mapper.StudentMappers">
<select id="findbyid" parameterType="Integer" resultMap="StudentResult">
select *from student where id=#{id}
</select>

<select id="findbygradeid" parameterType="Integer" resultMap="StudentResult">
select *from student where gid=#{gid}
</select>

<select id="findbygradeid2" parameterType="Integer" resultType="com.qbd.mapper.AddressMappers.findbyid">
select *from student where gid=#{gid}
</select>

<resultMap type="Student" id="StudentResult">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property="address" column="addid" select="com.qbd.mapper.AddressMappers.findbyid">
</association>
<association property="grade" column="gid" select="com.qbd.mapper.GradeMappers.findbyid">
</association>
</resultMap>
</mapper>

2.mybatis转义符

在mapper文件中直接写<会出错，sql预编译时出错，项目都运行不起来。这时就要用转义符

1、在xml的sql语句中，不能直接用大于号、小于号要用转义字符

如果用小于号会报错误如下：

org.apache.ibatis.builder.BuilderException: Error creating document instance. Cause: org.xml.sax.SAXParseException: The content of elements must consist of well-formed character data or markup.

转义字符

这样的问题在MyBatis中或者自定义的xml处理sql的程序中经常需要我们来处理。其实很简单，我们只需作如下替换即可避免上述的错误：

原符号	<	<=	>	>=	&	'	"
替换符号	<	<=	>	>=	&	'	"

2、使用

<![CDATA[ ]]>标记的sql语句中的<where> <if>等标签不会被解析
举例如下：

SELECT * FROM  user WHERE  age  <= 30 AND age >= 18

<update id="updateSearchControlFeedback">

update SEARCH_CONTROL_FEEDBACK set IS_ARRETED = #{isArreted}

,FEEDBACK_TIME=#{feedbackTime}

,EVENT_STATUS = #{newEventStatus}

where EVENT_STATUS=#{oldEventStatus}

<![CDATA[ AND RECEIVE_TIME <= #{receiveTime} ]]>

</update>