Idea中的Mybaties中配置文件的mapper无法找到xml文件！

这是错误信息

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error building SqlSession.
### The error may exist in com.dao.UserDao.xml
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource com.dao.UserDao.xml
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:80)
    at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:64)
    at test.main(test.java:21)
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource com.dao.UserDao.xml
    at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:121)
    at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:99)
    at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:78)
    ... 2 more
Caused by: java.io.IOException: Could not find resource com.dao.UserDao.xml
    at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:114)
    at org.apache.ibatis.io.Resources.getResourceAsStream(Resources.java:100)
    at org.apache.ibatis.builder.xml.XMLConfigBuilder.mapperElement(XMLConfigBuilder.java:371)
    at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:119)
    ... 4 more

Process finished with exit code 1

求解答

mapper的三种写法，你对下你的写法对吗?
接口用class （接口）

<mapper class="org.mybatis.mappers.UserMapper"/>

绝对路径用url （绝对路径）

<mapper url="file:///var/mappers/UserMapper.xml"/>

xml文件用resource（相对路径）

<mapper resource="org/mybatis/mappers/UserMapper.xml"/>

文件名前面加上类路经classpath:试试