GWT RF: How to share the same code in client and server

Question

I would like to use the same code to sort and manipulate objects in client and server sides.

But I am facing a problem since in client we need a proxy interface representing the class of the server.

Is there a way to use the same interface in both?, I know RF has a mechanism to copy bean attributes from the server instance to the client instance when it is sent through the wire.

Answer 1

As Thomas says in his answer, the only way in current GWT to have shared code in client and sever is implementing the same interface in both sides and using it in your shared code.

Since RF copies attributes from the server to the client as you say in your query, in theory we could use the same interface (the proxy one) in both sides (simpler code), setting the @ValueFor value pointing to itself.

Lets see an example:

 // Shared interface in client and server sides
 @ProxyFor(Foo.class)
 interface Foo extends ValueProxy {
    String getBar();
 }

 // Server side implementation
 class FooImpl implements Foo {
    String getBar(){return "bar";};
 }

As information, we use this approach in our product, so as we can sell 2 backend solutions (one is based on GAE and other on couchdb).

The code above works for client code which does not create new values, but if you want to create them, it is enough to define a value locator:

 // Say RF which locator to use to create classes in server side
 @ProxyFor(value = Foo.class, locator ALocator.class)
 interface Foo extends ValueProxy {
 }

 public class ALocator extends Locator<Foo, String>  {
   public Foo create(Class<? extends Foo> clazz) {
    return new FooImpl();
   }
   ...
 }

Unfortunately, RF does not deal with interfaces in the server side see issues: 7509 and 5762.

But, as you can read in the issues comments, there is already a fix for this (pending for review). Hopefully it would be included in a next release of GWT.

In the meanwhile, you can use this approach, just copying the file ResolverServiceLayer.java in your src folder and applying this patch to it.