我公司有一个web的系统，java部署的，在Windows Server 2008 R2服务器上使用正常，但因为Windows Server不稳定，经常宕机，所以想使用CentOS 6 部署。换过去以后，登录页能打开，输入账号登录后就报错如下：

HTTP Status 500 - java.lang.NullPointerException

exception

javax.servlet.ServletException: java.lang.NullPointerException
	org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:535)
	org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:433)
	org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
	org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
	org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:643)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
	all.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:62)

root cause

java.lang.NullPointerException
	java.lang.Class.forName0(Native Method)
	java.lang.Class.forName(Class.java:171)
	all.Usedb.<init>(Usedb.java:27)
	all.Kfpro.dengluchuli(Kfpro.java:127)
	com.yourcompany.struts.action.LoginAction.execute(LoginAction.java:69)
	org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
	org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
	org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
	org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:643)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
	all.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:62)

使用的是jdk1.6.0_45，tomcat6，都是默认设置，同样版本的java和tomcat也是默认设置在Windows Server上就没这个问题。环境啥的应该没问题，tomcat默认页面都能打开。我也不懂Java，只会部署，请问这个是什么问题。