How to call JSON-RPC services using RequestFactory - gwt

Question

Or what is the best way to archive this on GWT.
Please post some code of how to call a simple service with parameters using RequestFactory.
UPDATE:
Thomas, i have updated my code with your suggestions.
public interface MyRequestFactory extends RequestFactory {
MyRequestFactory INSTANCE = GWT.create(MyRequestFactory.class);
MyRequestContext myRequestContest();
}
#JsonRpcService
public interface MyRequestContext extends RequestContext {
UserFullFormattedName userFullFormattedName();
#JsonRpcWireName(value = "GetUserFullFormattedName")
public interface UserFullFormattedName extends Request<String> {
}
}
public static EventBus EVENT_BUS = GWT.create(SimpleEventBus.class);
public void onModuleLoad() {
DefaultRequestTransport requestTransport = new DefaultRequestTransport();
requestTransport.setRequestUrl("../services/service.ashx");
MyRequestFactory.INSTANCE.initialize(EVENT_BUS, requestTransport);
MyRequestFactory.INSTANCE.myRequestContext().userFullFormattedName().fire(new Receiver<String>() {
#Override
public void onSuccess(String response) {
System.out.println(response);
}
});
This code fails with:
11:37:49.722 [ERROR] [modules] Uncaught exception escaped
java.lang.AssertionError: java.lang.String is not an EntityProxy type
at com.google.web.bindery.requestfactory.shared.impl.IdFactory.asEntityProxy(IdFactory.java:66)
at com.google.web.bindery.requestfactory.shared.impl.IdFactory.createId(IdFactory.java:229)
at com.google.web.bindery.requestfactory.shared.impl.IdFactory.allocateId(IdFactory.java:41)
at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$JsonRpcPayloadDialect.processPayload(AbstractRequestContext.java:251)
at com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext$5.onTransportSuccess(AbstractRequestContext.java:1108)
at com.google.web.bindery.requestfactory.gwt.client.DefaultRequestTransport$1.onResponseReceived(DefaultRequestTransport.java:136)
at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:287)
at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:395)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:337)
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:218)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:561)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:269)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:213)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:292)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:546)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:363)
at java.lang.Thread.run(Unknown Source)

Answer 1

Cat should be a ValueProxy annotated with #JsonRpcProxy:
#JsonRpcProxy
interface Cat extends ValueProxy {
String getName();
String getId();
}
Also, I'm not sure the #JsonRpcWireName is required, as its value is the same as the method name.