转：http://blog.csdn.net/liuxuejin/article/details/7226983
org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:522)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:356)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:416)
org.apache.struts2.dispatcher.ActionContextCleanUp.doFilter(ActionContextCleanUp.java:99)
Apache Software Foundation/Tomcat6.0/webapps/你的工程/WEB-INF/lib下面看有没有servlet-api.jar、jsp-api.jar 等在Apache Software Foundation/Tomcat6.0/lib 下面已经存在的jar包， 如果有则删除。重启后，问题解决。