GWT error "no instantiable subtypes" with interface in RPC method with 1 known concrete class?

[Ed]

I have added the following async remote service method (using 2.7.0.):

TransportTokenResponse<ProductDto> findActiveDeclarationsOfActiveMember(TransportTokenRequest<Void> request);

TransportTokenResponse, just like TransportTokenRequest are interfaces with both an abstract subclass and one concrete class.

The GWT console shows the following error:

   ERROR] 'com.ited.lang.transporttoken.TransportTokenResponse' has no instantiable subtypes 

I am aware that using interfaces in RPC methods is tricky and can result in bloat code, but in this case, I only have one concrete class, so why does GWT complain and can't use the concrete class (it's in the same package as the interface) ?

I noticed this is a new 2.7.0. warning, maybe it has something to do with this

The details of TransportTokenResponse,:

public abstract class TransportTokenResponseBase<T> implements TransportTokenResponse<T> {
 private static final long serialVersionUID = 1L;

 protected TransportTokenResponseBase() {
 }
}


public final class SimpleTransportTokenResponse<T> extends TransportTokenResponseBase<T> {
 private static final long serialVersionUID = 1L;
    SimpleTransportTokenResponse() {
 }
}

[Ed]

Sorry for being impatient ;)..

Anybody an idea ? (interface not allowed at all in RPC method calls? )

[Jens]

Sorry for being impatient ;)..

Anybody an idea ? (interface not allowed at all in RPC method calls? )

No idea. Might be a bug... or intended ;-) Maybe GWT explicitly searches for a class that implements TransportTokenResponse<ProductDto> and does not care about your <T> implementation.

Does it work if you add

SimpleTransportTokenResponse<ProductDto> dummyMethod();

to your service?

-- J.

[rhmoller]

Are the classes visible to GWT? I don't see .client. or .shared. in the package com.ited.lang.transporttoken.TransportTokenResponse so double check the source entries in your gwt.xml file

/Rene

[rhmoller]

and check that the request and response interfaces are marked Serializable

/Rene

[Ed Bras]

@Rhmoller: thanks. Yes they are marked as Serializable. And yes they are visible to gwt, when I create a instance in gwt code, it results in no error.​ I hardly ever use client, shared, server packages..

I get that impression that GWT does't allow interfaces (anymore) in RPC methods. This is the new 2.7.0 code that shows me the error: LINKE

@Jens: thanks. I am about to try that (using concrete classes), let me get back on that.

[Jens]

I get that impression that GWT does't allow interfaces (anymore) in RPC methods. This is the new 2.7.0 code that shows me the error: LINKE

That patch just gives you a better error message. Before that you would get something like "Failed to resolve 'my.package.MyService' via deferred binding".

-- J.

[Ian White]

If you have a class that you are using to transport RPC params then it needs to implement IsSerializable, right.

So then if your IsSerializable class does not have a default empty constructor (i.e. no params) you will see this message.