Yes SERVICE is a remote service.

Code:
RpcProxy<String> proxy = new RpcProxy<String>() {

            @Override
            protected void load(Object loadConfig, AsyncCallback<String> callback) {
                SERVICE.getSampleJson(callback);
            }
        };

         ModelType type = new ModelType();
         type.setRoot("datatable");
         type.addField("adi","adi");
         type.addField("soyadi","soyadi");

         JsonLoadResultReader<ModelData> reader = new JsonLoadResultReader<ModelData>(type);
         BaseListLoader<BaseListLoadResult<ModelData>> loader = new BaseListLoader<BaseListLoadResult<ModelData>>(proxy,reader);
         ListStore<ModelData> store = new ListStore<ModelData>(loader);
         
         store.addStoreListener(new StoreListener<ModelData>(){

            @Override
            public void storeDataChanged(StoreEvent<ModelData> se) {
                MessageBox.alert("aa", se.getStore().getModels().get(0).get("adi").toString(), null);
            }
            
         } );

         loader.load();
this code its work but how to handle exception as GWT rpc service with GXT RPCProxy?