错误原因:
编译时没有编译xml映射文件
解决方案:
在pom中加入以下配置
<!--可以将xml文件也编译-->
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.*</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
</build>