EL 3.0 中的常量 - 未找到函数“T”

Question

我相信 EL 3.0 中常量的语法是 #{T(java.lang.Integer).MIN_VALUE}，但 glassfish 会抛出 javax.el.ELException: Function 'T' not found。这是完整的堆栈跟踪：

javax.el.ELException: Function 'T' not found
    at com.sun.el.parser.AstFunction.getValue(AstFunction.java:186)
    at com.sun.el.parser.AstValue.getBase(AstValue.java:151)
    at com.sun.el.parser.AstValue.getValue(AstValue.java:200)
    at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:226)
    at org.jboss.weld.el.WeldValueExpression.getValue(WeldValueExpression.java:50)
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109)
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:194)
    at javax.faces.component.html.HtmlInputText.getSize(HtmlInputText.java:600)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at javax.faces.component.UIComponentBase$AttributesMap.get(UIComponentBase.java:2389)
    at org.primefaces.renderkit.CoreRenderer.renderPassThruAttributes(CoreRenderer.java:111)
    at org.primefaces.component.inputtext.InputTextRenderer.encodeMarkup(InputTextRenderer.java:82)
    at org.primefaces.component.inputtext.InputTextRenderer.encodeEnd(InputTextRenderer.java:51)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:924)
    at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:63)
    at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:47)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeContent(FieldsetRenderer.java:90)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeMarkup(FieldsetRenderer.java:72)
    at org.primefaces.component.fieldset.FieldsetRenderer.encodeEnd(FieldsetRenderer.java:46)
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:924)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
    at javax.faces.render.Renderer.encodeChildren(Renderer.java:176)
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:894)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1856)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:443)
    at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:337)
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:120)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:219)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:647)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
    at java.lang.Thread.run(Thread.java:722)

Answer 1

#{T(java.lang.Integer).MIN_VALUE} 语法确实在EL 3.0 early draft review 和EL 3.0 proposal homepage 中都被提及。但是，在 EL 3.0 final release 中，它在最后一刻被删除并替换为更简单的 #{Integer.MIN_VALUE} 语法。

然而，新语法又在 GlassFish4 中有一个错误：它是由新的独立 EL 处理器 API 实现的，而不是由 JSP API 实现的。这已被报告为issue 20778 并在半小时前修复。换句话说：您需要升级 GlassFish4。

Answer 2

在这种情况下，T 代表“类型”。在您的实际代码中，您将引用您所引用的类的 EL 名称。因此，例如，对于以下支持 bean 类：

@Named
public class MyBackingBean {
  public static final Integer MIN_VALUE = new Integer(10);
...
}

在 EL 中，您将其称为：

#{myBackingBean.MIN_VALUE}

虽然我个人不会在这里使用Integer 作为常量，但int 会起作用。