Modified the code , it is working now. Thanks for the help
//
//Method in the ComposerEditorContainer class
//
	public ComposerProxy save() {
		ComposerRequest composerRequest = (ComposerRequest) editorDriver
				.flush();
		final ComposerProxy newProxy = composerRequest.edit(composer);
		composerRequest.persist(newProxy).fire(new Receiver<Boolean>() {
			public void onSuccess(Boolean arg0) {
				if (arg0)
					presenter.updateEditor();
			}});
		return newProxy;
	}
//
//Method in the presenter
//
	public void updateEditor() {
		requestFactory = GWT.create(AppRequestFactory.class);
		requestFactory.initialize(new SimpleEventBus());
		ComposerRequest request = requestFactory.getComposerRequest();
		Request<ComposerProxy> req = request.findComposer(selectedComposer
				.getId());
		req.fire(new Receiver<ComposerProxy>() {
			public void onSuccess(ComposerProxy arg0) {
				selectedComposer = arg0;
				editorContainer.setComposer(selectedComposer);
				editorContainer.edit(requestFactory.getComposerRequest());
				view.clear();
				view.addWidget(editorContainer);
			}});
	}
	public void registerEvents() {
		eventBus.addHandler(SaveButtonClickedEvent.TYPE,
				new SaveButtonClickedEventHandler() {
					@Override
					public void onSaveButtonClicked(SaveButtonClickedEvent event) {
						selectedComposer = ((ComposerEditorContainer)
editorContainer).save();
					}
				});
		eventBus.addHandler(BrowserItemClickedEvent.TYPE,
				new BrowserItemClickedEventHandler() {
					@Override
					public void onBrowserItemClicked(
							BrowserItemClickedEvent event) {
						requestFactory = GWT.create(AppRequestFactory.class);
						requestFactory.initialize(new SimpleEventBus());
						ComposerRequest request = requestFactory
								.getComposerRequest();
						Request<ComposerProxy> req = request.findComposer(event
								.getclickedItem().getValue());
						req.fire(new Receiver<ComposerProxy>() {
							public void onSuccess(ComposerProxy arg0) {
								selectedComposer = arg0;
								editorContainer.setComposer(selectedComposer);
								editorContainer.edit(requestFactory
										.getComposerRequest());
								view.clear();
								view.addWidget(editorContainer);
							}
						});
					}});