I'm being stuck for hours on this simple implementation of the GWT SimpleEventbus.
Is there anything wrong with this setup? What could be a possible reason for this?
I'm using the web.binderyEventbus
import com.google.web.bindery.event.shared.SimpleEventBus;
The Eventbus is initalized in my Entrypoint Class.
public void onModuleLoad() {
ApplicationEvents = new SimpleEventBus();
It's then injected into the Singleton LoadData and into the MainView (UIBinder class no MVP).
LoadData.initLoadData(ApplicationEvents);
view = new MainView(ApplicationEvents);
initLoadData is basically an alias for the constructor, except that it's not returning anything.
public class LoadData {
private final SimpleEventBus eventBus;
private LoadData(final SimpleEventBus bus) {
eventBus = bus;
...
}
public static void initLoadData(final SimpleEventBus bus){
if (instance == null){
instance = new LoadData(bus);
}
}
The Eventbus is injected to the MainView like this.
public class MainView extends Composite {
private final SimpleEventBus eventbus;
public MainView(final SimpleEventBus bus) {
eventbus = bus;
...
Then the handler is registered.
eventbus.addHandler(EntriesReceiveEvent.TYPE, new EntriesReceiveEventHandler() {
@Override
public void onEntriesReceive(EntriesReceiveEvent event) {
...
}
});
And at the end of the method I have it call a method in LoadData.
LoadData.getLoadData().fetchYears(); //alias for loadIndex
The loadIndex method in LoadData.java
private void loadIndex() {
System.out.println(eventBus.toString());
if(indexEntries == null){
AsyncCallback..
public void onSuccess(Map<Short, IndexEntry> result) {
eventBus.fireEvent(new EntriesReceiveEvent());
//^^ LoadData.java:190
EntriesReceiveEvent.java
import com.google.gwt.event.shared.GwtEvent;
public class EntriesReceiveEvent extends GwtEvent<EntriesReceiveEventHandler> {
public static Type<EntriesReceiveEventHandler> TYPE =
new Type<EntriesReceiveEventHandler>();
@Override
public Type<EntriesReceiveEventHandler> getAssociatedType() {
return TYPE;
}
@Override
protected void dispatch(EntriesReceiveEventHandler handler) {
handler.onEntriesReceive(this);
}
}
And it's handler EntriesReceiveEventHandler.java
import com.google.gwt.event.shared.EventHandler;
public interface EntriesReceiveEventHandler extends EventHandler {
void onEntriesReceive(EntriesReceiveEvent event);
}
Finally the Exception.
11:36:57.417 [ERROR] [] Uncaught exception escaped
com.google.web.bindery.event.shared.UmbrellaException: Exception caught: null
at com.google.web.bindery.event.shared.SimpleEventBus.doFire(SimpleEventBus.java:203)
at com.google.web.bindery.event.shared.SimpleEventBus.fireEvent(SimpleEventBus.java:88)
at com.SoftwareEngineering.client.LoadData$2.onSuccess(LoadData.java:190)
at com.SoftwareEngineering.client.LoadData$2.onSuccess(LoadData.java:1)
at com.google.gwt.user.client.rpc.impl.RequestCallbackAdapter.onResponseReceived(RequestCallbackAdapter.java:232)
at com.google.gwt.http.client.Request.fireOnResponseReceived(Request.java:258)
at com.google.gwt.http.client.RequestBuilder$1.onReadyStateChange(RequestBuilder.java:412)
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:338)
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:571)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:279)
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:242)
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:293)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
at java.lang.Thread.run(Unknown Source)
I thought that the Eventbus might not be the same as I didn't know if they're all talking to the same Eventbus. This site however proved my concerns to be wrong.
Side question: Do you consider the Singleton in this context bad? It's a rather small project and the LoadData which handles all RPC requests needs to be globally available.
Thank you for any help!