关于web登录出现的问题求解

wch100

Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: java.lang.NullPointerException
        org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:286)
        org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
        org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        com.filter.EncodingFilter.doFilter(EncodingFilter.java:25)
root cause

java.lang.NullPointerException
        com.dao.ManagerDAO.checkManager(ManagerDAO.java:77)
        com.action.Manager.managerLogin(Manager.java:52)
        com.action.Manager.execute(Manager.java:24)
        org.apache.struts.chain.commands.servlet.ExecuteAction.execute(ExecuteAction.java:5
        org.apache.struts.chain.commands.AbstractExecuteAction.execute(AbstractExecuteAction.java:67)
        org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
        org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
        org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:304)
        org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:190)
        org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
        org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
        org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
        javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        com.filter.EncodingFilter.doFilter(EncodingFilter.java:25)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.13 logs.
这算是什么问题？求大神们帮忙看看