CODEWITHSUNDEEP
gwt
sof
sof

Reputation: 9649

GWT Uncaught IllegalArgumentException

Sometimes my GWT app reports an "Uncaught IllegalArgumentException" below. The error log effectively masks any possible cause from the app. How would you pin down the source of the problem pragmatically in this case?

[ERROR] [mygwtapp] Uncaught exception escaped

java.lang.IllegalArgumentException: Something other than a Java object was returned from JSNI method '@com.google.gwt.core.client.impl.Impl::apply(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)': JS value of type boolean, expected java.lang.Object
    at com.google.gwt.dev.shell.JsValueGlue.get(JsValueGlue.java:178)
    at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:271)
    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.GeneratedMethodAccessor24.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    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(Thread.java:662)

Upvotes: 0

Views: 2836

Answers (3)

Joseph Lust
Joseph Lust

Reputation: 19975

With JSNI, you must return only:

  • Objects that extend JavaScriptObject
  • Primitives & String (no long since there is not one in JS)
  • Java Object or array that came from Java code

So you can return boolean or make your own overlay type if primitives don't meet your needs. But otherwise stick with the primitive boolean.

Upvotes: 2

Hardik Mishra
Hardik Mishra

Reputation: 14877

This error occurs when you have type mismatch from return value of called JSNI function.

For example:

public class GWTTest implements EntryPoint 
{ 
    public void onModuleLoad() { 
        if(get()==false){ 
            System.out.println(get()); 
        } 
    } 
    private native Boolean get()/*-{ 
        return false; 
    }-*/; 
}

Here you will get error "java.lang.IllegalArgumentException: Something other than a Java object was returned from JSNI method"

Remember: There is no autoboxing in javascript.

You should return boolean, not Boolean.

Upvotes: 2

Thomas Broyer
Thomas Broyer

Reputation: 64541

In case you're not using Chrome, in which case it's a known bug and the only solution is to switch to Firefox or IE for DevMode or wait for SuperDevMode (expected for GWT 2.5, to be released in a month or so), then your best bet is to try to reproduce it in prod mode.

You could also check your JSNI methods (because it would likely come from your own code), for one that could possibly return a boolean instead of an object (tin this specific case).

Upvotes: 3

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