Java Web应用程序错误-Can'；我不明白为什么'；现在发生了什么

我正在使用eclipse，我可以构建webapp并将其部署到Jboss4.2.1。它以前是工作的，我并没有做任何真正广泛的改变来产生这个错误。当我通过浏览器访问webapp时，我以前一直使用通用用户名登录，然后我可以像往常一样使用我的webapp

现在，当我通过浏览器访问webapp时，这个错误会反复出现，并且不会显示任何内容。以下是我收到的错误：

07:55:06,174 INFO  [security] User '' attempting login via SiteMinder...
07:55:06,174 INFO  [security] User '' attempting login via SiteMinder...
07:55:06,174 ERROR [[jsp]] Servlet.service() for servlet jsp threw exception
java.lang.LinkageError: Class javax/el/ExpressionFactory violates loader constraints
    at org.apache.jsp.WEB_002dINF.jsp.layout.header_jsp._jspx_meth_c_005fset_005f0(header_jsp.java:207)
    at org.apache.jsp.WEB_002dINF.jsp.layout.header_jsp._jspx_meth_c_005fif_005f0(header_jsp.java:179)
    at org.apache.jsp.WEB_002dINF.jsp.layout.header_jsp._jspService(header_jsp.java:82)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:387)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:687)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:590)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:505)
    at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:968)
    at org.apache.jasper.runtime.PageContextImpl.doInclude(PageContextImpl.java:643)
    at org.apache.jasper.runtime.PageContextImpl.include(PageContextImpl.java:637)
    at net.sourceforge.stripes.tag.layout.LayoutRenderTag.doEndTag(LayoutRenderTag.java:122)
    at org.apache.jsp.WEB_002dINF.jsp.layout.layout_jsp._jspx_meth_stripes_005flayout_002drender_005f0(layout_jsp.java:796)
    at org.apache.jsp.WEB_002dINF.jsp.layout.layout_jsp._jspx_meth_stripes_005flayout_002dcomponent_005f2(layout_jsp.java:759)
    at org.apache.jsp.WEB_002dINF.jsp.layout.layout_jsp._jspService(layout_jsp.java:200)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:387)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:687)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:590)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:505)
    at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:968)
    at org.apache.jasper.runtime.PageContextImpl.doInclude(PageContextImpl.java:643)
    at org.apache.jasper.runtime.PageContextImpl.include(PageContextImpl.java:637)
    at net.sourceforge.stripes.tag.layout.LayoutRenderTag.doEndTag(LayoutRenderTag.java:122)
    at org.apache.jsp.view.public_.login_jsp._jspService(login_jsp.java:335)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:387)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at net.sourceforge.stripes.controller.StripesFilter.doFilter(StripesFilter.java:180)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:112)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:265)
    at org.acegisecurity.ui.switchuser.SwitchUserProcessingFilter.doFilter(SwitchUserProcessingFilter.java:341)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.intercept.web.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:107)
    at org.acegisecurity.intercept.web.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:72)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:110)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:110)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.wrapper.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:81)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:229)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:229)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:286)
    at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
    at org.acegisecurity.util.FilterChainProxy.doFilter(FilterChainProxy.java:149)
    at org.acegisecurity.util.FilterToBeanProxy.doFilter(FilterToBeanProxy.java:98)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179)
    at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
    at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:580)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
    at java.lang.Thread.run(Thread.java:595)

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任何帮助都将不胜感激

我确信您必须重新启动服务…

运行时类路径可能被重复和/或不同版本的EL API污染

通常，EL API已经随servletcontainer/appserver一起提供。您不应该以任何方式复制/复制/移动它的库到其他地方，比如webapp的

/WEB-INF/lib

，或者更糟糕的是JRE的

/lib

。从所有重复和/或不同版本的类/JAR文件中清除类路径。否则可能会导致类似的例外情况

---

初学者的一个常见错误是，他们将servletcontainer/appserver的库复制到

/WEB-INF/lib

中，因为他们在IDE中遇到编译错误（

javax.servlet

未找到等等）。复制库是错误的解决方案。您应该将服务器集成到同一个IDE中，并将IDE项目配置为引用/关联相关的服务器，以便IDE将自动在项目的构建路径中获取其库。

谷歌搜索一下，表明其他应用程序也有类似的问题，通常是由于el库的一些兼容性问题。您可以检查一下。

我遇到了一个类似的例外，尽管在完全不同的上下文中，但在这里也应该有效

通常这意味着您在类路径中有多个违规类的副本

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我会尝试查找javax.el.ExpressionFactory.class是否多次出现。（可能在服务器库和应用程序库中都有）

非常感谢。你的信息帮了大忙，我已经解决了这个问题。