Overriding processCall to intercept RPC calls

[joe kolba]

I needed a solution to intercept RPC calls to make sure the user session hasn't expired.  Here is my code:

@Override
    public String processCall(String payload) throws SerializationException {

        boolean validSession = (!getThreadLocalRequest().getSession().isNew());
           
        RPCRequest rpcRequest =  RPC.decodeRequest(payload, this.remoteServiceClass);
           
        if(!validSession && !rpcRequest.getMethod().getName().equalsIgnoreCase("isUserLoggedIn")){
            return RPC.encodeResponseForFailure(null, new IncompatibleRemoteServiceException("Logged out"));
        }else{
            return super.processCall(payload);
        }
       
      }

Everything works however I had to use the IncompatibleRemoteServiceException rather then a custom exception.  Whenever I tried to use my custom exception or IllegalArgumentException with RPC.encodeResponseForFailure() I would get a 500 response from my RPC call.  Anyone have any information that could help me return a custom exception?

[Paul Stockley]

In your service interface you have do declare each function throws your custom exception otherwise you will get that error.

[joe kolba]

I am throwing IllegalArgumentException in my service interface and i still get the 500 error.

On Tue, Jan 3, 2012 at 1:22 PM, Paul Stockley <pstoc...@gmail.com> wrote:

In your service interface you have do declare each function throws your custom exception otherwise you will get that error.

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[joe kolba]

return RPC.encodeResponseForFailure(null, new IllegalArgumentException("Logged out"));


service interface...

public interface GreetingService extends RemoteService {
        boolean isUserLoggedIn() throws IllegalArgumentException;

[Ashton Thomas]

May also be a good idea to have all your services declare "throws SerializationException" and have all your custom exceptions extend SerExc

Joe, did you fix your problem? if not, can you provide more details?

[joe kolba]

I solved it by creating a custom exception that extended IncompatibleRemoveService exception... it seems that is the only exception that RPC can serialize for failure.

On Tue, Jan 3, 2012 at 1:39 PM, Ashton Thomas <ash...@acrinta.com> wrote:

May also be a good idea to have all your services declare "throws SerializationException" and have all your custom exceptions extend SerExc

Joe, did you fix your problem? if not, can you provide more details?

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[joe kolba]

im sorry i meant i extended RuntimeException not IncompatibleRemoteService

[Jens]

Instead of this I would just extend RemoteServiceServlet and add a public static method that makes the session available to everyone (just like RequestFactoryServlet does), e.g.

public static HttpSession getThreadLocalSession() {

  return getThreadLocalRequest().getSession();

}

Then in your service method:

public boolean isUserLoggedIn() throws IllegalArgumentException {

  HttpSession session = YourExtendedRemoteServiceServlet.getThreadLocalSession();

  if(session.isNew()) {

    throw new IllegalArgumentException("Logged out");

  }

}

That way you actually see the session check at the correct place and not hidden in your RemoteServiceServlet implementation.

-- J.

[joe kolba]

yeah i was thinking about doing that but im going to have to call that static method for every rpc method, which I have around 15.  Thanks I will consider changing it to this.

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[Jens]

You could also implement it using a ServletFilter. Take a look at the mobile web app example from GWT which uses a ServletFilter to authenticate users against Google App Engine:

http://code.google.com/p/google-web-toolkit/source/browse/releases/2.4/samples/mobilewebapp/src/main/java/com/google/gwt/sample/gaerequest/server/GaeAuthFilter.java 

Then simply add the Filter to your web.xml.

-- J.