报错org.springframework.beans.factory.BeanCreationException:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘sqlsession’ defined in class path resource [applicationContext.xml]: Invocation of init method failed; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: ‘file [D:\spring代码.metadata.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\ssm-studentInfoManager\WEB-INF\classes\mapper\mapper.xml]’; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: org.apache.ibatis.builder.BuilderException: Mapper’s namespace cannot be empty
这种错误前面就显示映射错误，其实就是后面加粗的那后面一句：mapper文件中的命名空间不能为空。