Overriding JSNI methods causes crash ?

[Pierre]

Hi all,

I am experiencing problems when using GWT / JSNI :

For tests, let's have a parent class with a JSNI method such as
public class TestParent {
public native void show()/*-{
$doc.write("PARENT JSNI");
}-*/;
}

and a child class overriding the parent JSNI method, such as
public class TestChild extends TestParent {
@Override
public void show() {
super.show();
RootPanel.get().add(new HTML("TestChild.show"));
}
}

and a basic EntryPoint :
public class Helloworld implements EntryPoint {

public void onModuleLoad() {
TestChild t = new TestChild();
t.show();
}
}

When calling the TestChild .show() method, we could assume getting the
result :
"PARENT JSNI" + "TestChild.show"

And in fact, we get the following result :
On Google Chrome 11 in development mode with GWT plugin :
"PARENT JSNI" and an error in the GWT plugin Development mode tab :

[DEBUG] [helloworld] - Rebinding
com.google.gwt.user.client.impl.WindowImpl
[DEBUG] [helloworld] - Checking rule <replace-with
class='com.google.gwt.user.client.impl.WindowImplIE'/>
[ERROR] [helloworld] - Error while executing the JavaScript provider
for property 'user.agent'
[ERROR] [helloworld] - Unable to get value of property 'user.agent'
[ERROR] [helloworld] - Deferred binding failed for
'com.google.gwt.user.client.impl.WindowImpl'; expect subsequent
failures
[ERROR] [helloworld] - Unable to load module entry point class
fr.helloworld.client.Helloworld (see associated exception for details)
[ERROR] [helloworld] - Failed to load module 'helloworld' from user
agent 'Mozilla/5.0 (Windows NT 5.1) AppleWebKit/534.24 (KHTML, like
Gecko) Chrome/11.0.696.0 Safari/534.24' at localhost:2222

This error stops any further instruction in the application.

On Firefox 3.6 in development mode with GWT plugin:
"PARENT JSNI" + "TestChild.show" (fine) but the browser is redirected
to http://127.0.0.1:8888/helloworld/hosted.html?helloworld and keeps
loading forever

When building the GWT project, the result are also different :
Chrome :
correct , works fine

Firefox 3.6 :
correct text displayed but the browser is redirected to helloworld/
F0E90C8F76FAE58BAB597BFF7095D19A.cache.html (compiled version for
firefox user agent) and keeps loading forever. I encountered the
problem on a real application, and of course the compiled application
was unable to run correctly.

Should I conclude that developer should never try to override JSNI
methods ?
Should we guess that it is a GWT compiler bug ?

[Andi]

maybe you should try "console.log" or "window.alert" instead of document.write..

andi

(vom fon)

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[Pierre]

Thanks for you answer,

In fact, solutions that don't write in the page (such as alert or
console) do work but it doesn't explain why the problems happens when
I use document.write

On 10 mar, 10:52, Andi <andi.ba...@googlemail.com> wrote:
> maybe you should try "console.log" or "window.alert" instead of document.write..
>
> andi
>
> (vom fon)
>

> > tohttp://127.0.0.1:8888/helloworld/hosted.html?helloworldand keeps

[Thomas Broyer]

document.write(), unless executed synchronously as the document loads, implies document.open() which replaces the current document with a new, blank one (similar to navigating to about:blank).