[MyBatis日记]问题汇总

Posted 2020-06-14 SunnyYoona

问题一：mybatis映射文件insert不执行，而直接用sql则可以插入成功

解决方案：

studentMapper.insertStudent(student);在执行晚SQL语句之后，记得session.commit();

问题二：中文显示乱码问题

解决方案：

配置数据库地址时加上编码格式characterEncoding： <property name="url" value="jdbc:mysql://localhost:3306/test?characterEncoding=utf8"/>

问题三：XML文件中大于号小于号问题

解决方案一：用了转义字符把>和<替换掉

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 
<mapper namespace="com.sjf.mapper.CourseMapper">
 
	<resultMap id = "CourseResultMap" type="com.sjf.bean.Course" >
		<id property="ID" column="ID"/>
		<result property="name" column="name"/>
		<result property="desc" column="description"/>
		<result property = "startDate" column = "startDate"/>
		<result property = "endDate" column = "endDate"/>
	</resultMap>
	
	<select id="getCourseByCondation" parameterType="hashmap" resultMap="CourseResultMap"> 
    	SELECT * FROM Course 
    	WHERE teacherID = #{teacherID} 
    	<if test = "courseName != null" >
    		AND NAME = #{courseName}
    	</if>
    	<if test = "startDate != null">
    		AND startDate >= #{startDate}
    	</if>
    	<if test = "endDate != null">
    		AND endDate  <= #{endDate}
    	</if>
  	</select>
</mapper> 

转义字符表：

转义符	符号
&lt;	<（小于号）
&gt;	>（大于号）
&amp;	&（和）
&apos;	‘（单引号）
&quot;	"（双引号）

解决方案二：

因为这个是xml格式的，所以不允许出现类似“>”这样的字符，但是都可以使用<![CDATA[ ]]>符号进行说明，将此类符号不进行解析。

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 
<mapper namespace="com.sjf.mapper.CourseMapper">
 
	<resultMap id = "CourseResultMap" type="com.sjf.bean.Course" >
		<id property="ID" column="ID"/>
		<result property="name" column="name"/>
		<result property="desc" column="description"/>
		<result property = "startDate" column = "startDate"/>
		<result property = "endDate" column = "endDate"/>
	</resultMap>
	
	<select id="getCourseByCondation" parameterType="hashmap" resultMap="CourseResultMap"> 
    	SELECT * FROM Course 
    	WHERE teacherID = #{teacherID} 
    	<if test = "courseName != null" >
    		AND NAME = #{courseName}
    	</if>
    	<if test = "startDate != null">
    		<![CDATA[AND startDate >= #{startDate} ]]>
    	</if>
    	<if test = "endDate != null">
    		<![CDATA[AND endDate  <= #{endDate} ]]>
    	</if>
  	</select>
</mapper>