关于middlegen + hbm2java生成java文件的问题

我先是用middlegen生成一个xml文件放在C:\Sample\org\hibernate\sample下
然后修改setenv.bat文件

@echo off

rem -------------------------------------------------------------------
rem Setup environment for hibernate tools
rem -------------------------------------------------------------------

set JDBC_DRIVER=C:\Opensource\lib\mysql-connector-java-3.1.7-bin.jar
set HIBERNATE_HOME=C:\Opensource\hibernate-2.1

set CORELIB=%HIBERNATE_HOME%\lib
set LIB=..\lib
set PROPS=%HIBERNATE_HOME%\src
set CP=%JDBC_DRIVER%;%PROPS%;%HIBERNATE_HOME%\hibernate2.jar;%CORELIB%\commons-logging-1.0.3.jar;%CORELIB%\commons-collections-2.1.jar;%CORELIB%\commons-lang-1.0.1.jar;%CORELIB%\cglib-2.0-rc2.jar;%CORELIB%\dom4j-1.4.jar;%CORELIB%\odmg-3.0.jar;%CORELIB%\xml-apis.jar;%CORELIB%\xerces-2.4.0.jar;%CORELIB%\xalan-2.4.0.jar;%LIB%\jdom.jar;C:\Opensource\hibernate-extensions-2.1\tools\hibernate-tools.jar;

然后运行hbm2java c:\sample\org\hibernate\sample\*.xml --output=c:\sample\
结果总提示空指针的exception，那位朋友能帮忙看一下，谢谢了！