Question

i implemented an HttpSessionListener for my JSF App.

I have a List<HttpSession> Object for all the active Sessions to my Application. On every SessionCreated Event I add the actual HttpSession to this List. On login i added some Attributes to the active Session and replace the modified Session in the List. So far so good, it’s working. But now i created a PrimeFaces Datatable to display which Session is a unused Session. This means which Session doesn’t have the login attribute. The Login attribute is a simple String Object.

Here is the implementation of the Datatable:

<p:dataTable var="sessions" value="#{applicationListener.sessions}" paginator="false" id="dt_sessions">  
    <f:facet name="header">
        Sessions
    </f:facet>

    <p:column headerText="ID" style="font-size: 12px; text-align: center" >  
        #{sessions.id}
    </p:column>
    <p:column headerText="Name" style="font-size: 12px; text-align: center" >  
        #{sessions.attribute(login)}
    </p:column>
 </p:dataTable>

Tomcat throws an HTTP 500 Stacktrace:

Feb 6, 2013 2:00:50 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [Faces Servlet] in context with path [] threw     exception [/rmlcon.xhtml: Unable to find method [attribute] with [1] parameters] with root cause
javax.el.ELException: /rmlcon.xhtml: Unable to find method [attribute] with [1] parameters
at com.sun.faces.facelets.compiler.TextInstruction.write(TextInstruction.java:88)
at com.sun.faces.facelets.compiler.UIInstructions.encodeBegin(UIInstructions.java:82)
at com.sun.faces.facelets.compiler.UILeaf.encodeAll(UILeaf.java:183)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1782)
at org.primefaces.component.datatable.DataTableRenderer.encodeRegularCell(DataTableRenderer.java:741)
at org.primefaces.component.datatable.DataTableRenderer.encodeRow(DataTableRenderer.java:693)
at org.primefaces.component.datatable.DataTableRenderer.encodeTbody(DataTableRenderer.java:601)
at org.primefaces.component.datatable.DataTableRenderer.encodeRegularTable(DataTableRenderer.java:220)
at org.primefaces.component.datatable.DataTableRenderer.encodeMarkup(DataTableRenderer.java:192)
at org.primefaces.component.datatable.DataTableRenderer.encodeEnd(DataTableRenderer.java:74)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1786)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1779)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1782)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1782)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:424)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:124)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

I do not really understand why it is thrown. Please can someone explain me my mistake?

Thanks.

Answer 1

The correct method name is getAttribute(), not attribute().

#{sessions.getAttribute(login)}

Remember, you’re invoking a method, not accessing a property, so the get prefix is still mandatory.

---

Unrelated to the concrete problem, I’d fix var="sessions" to be var="session", because it concerns only one session instance, not multiple. Otherwise your code reads very confusing (i.e. it’s not self-documenting).

#{session.getAttribute(login)}