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我创建了一个（基于 JSP 的）自定义 EL 函数以在呈现的标记中使用。该函数将返回一个布尔值来决定是否需要在页面上呈现页面组件。我使用 <%@ taglib uri = "/WEB-INF/mine.tld" prefix = "g" %> 将它导入到 jsp 页面。

在第一次加载 jsp 页面时一切正常。单击按钮后，表单将提交，然后我收到诸如“未找到类加载器：实现我的 EL 函数的类”和“未找到函数”之类的错误。这里发生了什么？什么是修复？

实现该功能的类 (com.util.WebContextLoader) 作为实用程序类包含在战争中。

下面是堆栈跟踪。

09:22:31,112 ERROR [STDERR] java.lang.ClassNotFoundException: No ClassLoaders found for: com.util.WebContextLoader
09:22:31,112 ERROR [STDERR]     at org.jboss.mx.loading.LoadMgr3.beginLoadTask(LoadMgr3.java:212)
09:22:31,112 ERROR [STDERR]     at org.jboss.mx.loading.RepositoryClassLoader.loadClassImpl(RepositoryClassLoader.java:521)
09:22:31,112 ERROR [STDERR]     at org.jboss.mx.loading.RepositoryClassLoader.loadClass(RepositoryClassLoader.java:415)
09:22:31,112 ERROR [STDERR]     at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
09:22:31,112 ERROR [STDERR]     at java.lang.Class.forName0(Native Method)
09:22:31,112 ERROR [STDERR]     at java.lang.Class.forName(Class.java:169)
09:22:31,112 ERROR [STDERR]     at org.apache.el.lang.FunctionMapperImpl$Function.getMethod(FunctionMapperImpl.java:147)
09:22:31,112 ERROR [STDERR]     at org.apache.el.lang.FunctionMapperImpl.resolveFunction(FunctionMapperImpl.java:53)
09:22:31,112 ERROR [STDERR]     at org.apache.el.parser.AstFunction.getValue(AstFunction.java:71)
09:22:31,112 ERROR [STDERR]     at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
09:22:31,112 ERROR [STDERR]     at org.apache.jasper.el.JspValueExpression.getValue(JspValueExpression.java:101)
09:22:31,112 ERROR [STDERR]     at javax.faces.component.UIComponentBase.isRendered(UIComponentBase.java:390)
09:22:31,112 ERROR [STDERR]     at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1018)
09:22:31,112 ERROR [STDERR]     at javax.faces.component.UIForm.processDecodes(UIForm.java:209)
09:22:31,112 ERROR [STDERR]     at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1026)
09:22:31,112 ERROR [STDERR]     at javax.faces.component.UIViewRoot.processDecodes(UIViewRoot.java:540)
09:22:31,112 ERROR [STDERR]     at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:78)
09:22:31,112 ERROR [STDERR]     at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
09:22:31,112 ERROR [STDERR]     at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
09:22:31,112 ERROR [STDERR]     at javax.faces.webapp.FacesServlet.service(FacesServlet.java:265)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
09:22:31,112 ERROR [STDERR]     at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
09:22:31,112 ERROR [STDERR]     at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:182)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:432)
09:22:31,112 ERROR [STDERR]     at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
09:22:31,112 ERROR [STDERR]     at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:420)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
09:22:31,112 ERROR [STDERR]     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262)
09:22:31,112 ERROR [STDERR]     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
09:22:31,112 ERROR [STDERR]     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
09:22:31,112 ERROR [STDERR]     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446)
09:22:31,112 ERROR [STDERR]     at java.lang.Thread.run(Thread.java:619)


09:22:31,112 WARN  [lifecycle] org.apache.jasper.el.JspELException: /register.jsp(45,2) '#{g:displayPageComponent('registrationPage', 'regUnit')}' Function 'g:displayPageComponent' not found
javax.faces.FacesException: org.apache.jasper.el.JspELException: /register.jsp(45,2) '#{g:displayPageComponent('registrationPage', 'regUnit')}' Function 'g:displayPageComponent' not found
    at javax.faces.component.UIComponentBase.isRendered(UIComponentBase.java:393)
    at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1018)
    at javax.faces.component.UIForm.processDecodes(UIForm.java:209)
    at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1026)
    at javax.faces.component.UIViewRoot.processDecodes(UIViewRoot.java:540)
    at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:78)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:265)
    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 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:182)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:432)
    at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
    at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:420)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446)
    at java.lang.Thread.run(Thread.java:619)
Caused by: org.apache.jasper.el.JspELException: /register.jsp(45,2) '#{g:displayPageComponent('registrationPage', 'regUnit')}' Function 'g:displayPageComponent' not found
    at org.apache.jasper.el.JspValueExpression.getValue(JspValueExpression.java:107)
    at javax.faces.component.UIComponentBase.isRendered(UIComponentBase.java:390)
    ... 34 more
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2 回答 2

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java.lang.ClassNotFoundException：找不到类加载器：com.util.WebContextLoader

函数类显然有一个被调用的依赖项，该依赖项com.util.WebContextLoader在其直接类路径邻域中不可用。

这种间歇性发生表明类路径被重复的类/库污染，这些类/库分布在由不同类加载器加载的类路径上。我会开始清理类路径。删除和中的所有 webapp 特定的类/JRE/lib库。JRE/lib/extserver/lib

于 2010-04-23T16:11:29.477 回答
0

我在这些线程中找到了解决此问题的方法。

http://community.jboss.org/message/46380

http://community.jboss.org/message/46385

解决方案是通过向 pom.xml 添加以下依赖项将 jasper-el-6.0.18.jar 放入战争的 /web-inf/lib 文件夹中。

org.apache.tomcat 碧玉-el 6.0.18

此依赖项还将包括“el-api-6.0.18.jar”（参见http://repo1.maven.org/maven2/org/apache/tomcat/jasper-el/6.0.18/jasper-el-6.0。 18.pom），我们需要排除它。

于 2010-07-30T14:47:17.827 回答