我´我试图用h:commandlink调用jsf中的bottom，从bean下载pdf。
基本上是这样的：

@Begin(join = true)
    public void generatePDF() throws Exception {
         //create pdf on page
}

<h:commandLink action="#{bean.generatePDF()}"/>

但是，每当我启动服务器并从第一次开始单击，或在服务器上长时间不执行操作时，它都会给出：

WARN  [SeamPhaseListener] uncaught exception, passing to exception handler
  org.jboss.seam.ConcurrentRequestTimeoutException: Concurrent call to conversation
  at org.jboss.seam.core.Manager.restoreAndLockConversation(Manager.java:641)
  at org.jboss.seam.core.Manager.restoreConversation(Manager.java:603)
  at org.jboss.seam.jsf.SeamPhaseListener.afterRestoreView(SeamPhaseListener.java:392)
  at org.jboss.seam.jsf.SeamPhaseListener.afterServletPhase(SeamPhaseListener.java:230)
  at org.jboss.seam.jsf.SeamPhaseListener.afterPhase(SeamPhaseListener.java:196)
  at com.sun.faces.lifecycle.Phase.handleAfterPhase(Phase.java:175)
  at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:114)
  at com.sun.faces.lifecycle.RestoreViewPhase.doPhase(RestoreViewPhase.java:102)
  at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
  at javax.faces.webapp.FacesServlet.service(FacesServlet.java:265)
  ...
  Caused by: java.lang.IllegalStateException: No active conversation context

提前感谢：）