struts程序出错,需重启tomcat才可以工作....

有时访问时出现该错误,重启tomcat后又可正常,麻烦帮我分析下是什么问题... HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Unable to compile class for JSP
org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:97)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:346)
org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:414)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:472)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1056)
org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:261)
org.apache.struts.tiles.TilesRequestProcessor.processTilesDefinition(TilesRequestProcessor.java:237)
org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequestProcessor.java:300)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:231)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1164)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:397)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:170)
root cause Compile failed; see the compiler error output for details.
org.apache.tools.ant.taskdefs.Javac.compile(Javac.java:944)
org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:764)
org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:382)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:472)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1056)
org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:261)
org.apache.struts.tiles.TilesRequestProcessor.processTilesDefinition(TilesRequestProcessor.java:237)
org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequestProcessor.java:300)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:231)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1164)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:397)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:170)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.
--------------------------------------------------------------------------------Apache Tomcat/5.0.28