[MYFACES-2216] MyFaces suppresses runtime exceptions thrown in ActionListeners

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.2.6, 1.2.7-SNAPSHOT
• Fix Version/s: 1.2.8
• Component/s: JSR-252
• Environment: Tomcat 6.0.18, JRE 1.6.11
• Assignee: Leonardo Uribe
• Reporter: Dirk Möbius
• Created: 24/Apr/09 08:15
• Updated: 17/Nov/09 03:12
• Resolved: 26/Oct/09 18:26

Description

Have a look at the following stack trace when a custom ActionListener throws an unhandled exception:

com.myproject.validation.ValidationException
at com.myproject.controller.MyController.validate(MyController.java:50)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.el.parser.AstValue.invoke(AstValue.java:172)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
at org.apache.jasper.el.JspMethodExpression.invoke(JspMethodExpression.java:68)
at javax.faces.event.MethodExpressionActionListener.processAction(MethodExpressionActionListener.java:49)
at javax.faces.event.ActionEvent.processListener(ActionEvent.java:51)
at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:554)
at javax.faces.component.UICommand.broadcast(UICommand.java:124)
at javax.faces.component.UIViewRoot._broadcastForPhase(UIViewRoot.java:369)
at javax.faces.component.UIViewRoot.process(UIViewRoot.java:264)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:153)
at org.apache.myfaces.lifecycle.InvokeApplicationExecutor.execute(InvokeApplicationExecutor.java:32)
at org.apache.myfaces.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:103)
at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:76)
at org.apache.myfaces.custom.ppr.PPRLifecycleWrapper.execute(PPRLifecycleWrapper.java:68)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:151)

In MethodExpressionActionListener.processAction(ActionEvent), any exception is wrapped into an AbortProcessingException:

public void processAction(ActionEvent actionEvent) throws AbortProcessingException {
try {
Object[] params = new Object[]

{actionEvent}

;
methodExpression.invoke(elContext(), params);
} catch (Exception e)

{ throw new AbortProcessingException(e); }

}

Deeper down in the stack trace, any AbortProcessingException is silently ignored in method UIViewRoot.__broadcastForPhase(PhaseId phaseId) :

private void _broadcastForPhase(PhaseId phaseId) {
...
try

{ source.broadcast(event); }

catch (AbortProcessingException e)

{ // abort event processing // Page 3-30 of JSF 1.1 spec: "Throw an // AbortProcessingException, to tell the JSF implementation // that no further broadcast of this event, or any further // events, should take place." abort = true; break; }

...
}

Mojarra logs the exception at least (twice, in fact). But IMHO unhandled exceptions should make it to the top-level to be handled by custom error handlers or phase listeners. The spec is not explicit about unhandled exceptions in ActionListeners. Sec 3.4.7 ("Event broadcasting") simply states:

During event broadcasting, a listener processing an event may:

• Examine or modify the state of any component in the component tree.
• Add or remove components from the component tree.
• Add messages to be returned to the user, by calling addMessage on the
  FacesContext instance for the current request.
• Queue one or more additional events, from the same source component or a different one,
  for processing during the current lifecycle phase.
• Throw an AbortProcessingException, to tell the JSF implementation that no
  further broadcast of this event, or any further events, should take place.
• Call renderResponse() on the FacesContext instance for the current request.[...]
• Call responseComplete() on the FacesContext instance for the current request.[...]

The best solution, IMHO, would be that MyFaces stores the unhandled exception in its internal queued exception list (request param "org.apache.myfaces.errorHandling.exceptionList") so that it won't get lost and can be inspected by custom code later.