Redirecting in @PostConstruct method resulted in IllegalStateException

Question

According to the answer of BalusC, I used

FacesContext.getCurrentInstance().getExternalContext().redirect(url);

in my @PostConstruct method to stop JSF from rendering the view and redirect users. However, when I try to run the code, I still ran into the java.lang.IllegalStateException exception at the above line.

WARNING: StandardWrapperValve[Faces Servlet]: PWC1406: Servlet.service() for servlet Faces Servlet threw exception
java.lang.IllegalStateException
    at org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:524)
    at StudentManagedBean.CourseSummary.init(CourseSummary.java:55)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

UPDATE: I added the following line in my @PostConstruct method:

System.out.println("INIT " + FacesContext.getCurrentInstance().getExternalContext().isResponseCommitted());

and what I saw was INIT true. I wonder if the response is supposed to be committed BEFORE the @PostConstruct method is called?

I'd be very grateful if you could give me an advice.

I am pretty sure that even if the Response has been completed in PostConstruct then the rest of the JSF lifecycle will still be executed. Do you get an error doing this from the constructor instead? Is this an Ajax request? What JSF implementation and version are you using? — maple_shaft, Jul 25 '12 at 11:06
I'm using JSF 2.0. Besides, I must do it in `@PostConstruct` because I need to call a function from my EJB before redirecting. It's not an AJAX request too. — Mr.J4mes, Jul 25 '12 at 11:11
The response is committed because the response header has already been manipulated by the FacesServlet. This is different than the response being completed which means the body has been written to and finalized which doesn't happen until the Render phase. Redirecting at any point after the response has been committed will result in an IllegalStateException so your only choice is to forward. — maple_shaft, Jul 25 '12 at 14:18
This was properly addressed in [another answer of BalusC](http://stackoverflow.com/questions/12168043/redirect-in-postconstruct-causes-illegalstateexception) — hakamairi, Jul 15 '15 at 16:15

score 3 · Accepted Answer · answered Mar 30 '13 at 06:29

As mentioned in my update, the following line printed INIT true:

System.out.println("INIT " + FacesContext.getCurrentInstance().getExternalContext().isResponseCommitted());

I finally found why the above situation occurred. On my page, before the ManagedBean X, which contains the redirect function, was referenced by UIComponent A, another ManagedBean Y was referenced beforehand by UIComponent B that is placed above UIComponent A in the page structure. As a consequence, the response was partially committed by ManagedBean Y, which makes it impossible for ManagedBean X to send a redirect request.

score 2 · Answer 2 · answered Jul 25 '12 at 11:21

A redirect will not work here, because even though the response has been completed and finalized, JSF is not smart enough to avoid its typical routine of running through the lifecycle events anyway.

Instead you can try doing a Forward from a RequestDispatcher. A Forward is different from a redirect in the following ways:

Performed internally by the servlet
Browser is apathetic
original url stays intact

Here is some code that displays how this can be done...

RequestDispatcher dispatcher =
    ((ServletRequest) context.getExternalContext().getRequest())
    .getRequestDispatcher("/j_spring_security_logout");

try {
  dispatcher.forward((ServletRequest) context.getExternalContext().getRequest(),
  (ServletResponse) context.getExternalContext().getResponse());
} catch (ServletException e) {
  log.error("ServletException", e);
} catch (IOException e) {
  log.error("IOException", e);
}

By doing this you are ending the execution of the FacesServlet prematurely and forwarding it onto a different servlet altogether. I imagine that from this other servlet it might be possible to redirect to the desired location.

:( Is this this the only way to achieve what I want? Creating a new servlet seems a bit too much for the simple redirection that I need. — Mr.J4mes, Jul 25 '12 at 13:25

Redirecting in @PostConstruct method resulted in IllegalStateException

2 Answers2