Re: LiveConnect and/or JavaXPCOM

poorboywilly wrote:
> Hi guys, I'm having a bear of a time here trying to work with some
> Java code.  I've got an extension going in Firefox (the XUL,
> JavaScript, CSS is great) and an XPCOM component in C++ (my best
> language) to do most of the heavy lifting.  The last thing I need to
> do is interface with a Java library (Apache's Nutch) for a few calls.
> Having discovered JavaXPCOM and LiveConnect this seemed like cake, but
> the documentation is definitely spotty so when my own fiddling doesn't
> work I can't find anywhere to turn.
> 
> First, I already implemented an XPCOM component in C++ so I decided to
> do a Java XPCOM component.  I have the XULRunner 1.9 SDK which
> includes the Java interfaces for all the nsISupports and so forth.  I
> implemented ISupports, IModule, IFactory in a few Java classes as well
> as defined my own interface in an IDL, compiling the idl both to
> a .java file and a typelib.  All the JavaXPCOM stuff I can find deals
> almost entirely with calling XPCOM components from Java code, I cannot
> find info on a Java component.  I've tried putting the raw class files
> (and typelib) in the Firefox/components directory, as well as a .jar
> of my classes in there and Firefox won't seem to find the component
> like it does my C++ component (using XPCOMViewer extension).  What am
> I missing with the JavaXPCOM?
>

As far as I am aware, you cannot currently embed java xpcom components 
into xulrunner, rather (as you have seen you have to run the event loop 
from java). Javier Pedemonte, who I am _sure_ will respond to this with 
far better information than myself is the lead for xpcom and was, last 
time I heard was working on getting java to be called from normal 
xulrunner builds.

I think the bug tracking this is 
https://bugzilla.mozilla.org/show_bug.cgi?id=299263 but I am not sure 
what state it is in


> Then, I stumbled across LiveConnect, and I could seemingly create the
> Nutch Java classes in my JavaScript extension code with a simple "new
> Packages.foo.bar.Class()" statement.  I was able to create a "new
> java.lang.String("foo")", which had me excited.  But the only
> apparently useful documentation I can find on LiveConnect is using it
> to call code in applets (e.g. https://jdk6.dev.java.net/plugin2/liveconnect/).
> Well, I don't need an applet, I just need to call an arbitrary Java
> package, and not even from a website, from an extension. Perhaps I'm
> asking for too much?  I found a vague reference to placing the
> desired .jar in the jre/lib/ext folder, which I did, but when I do
> that the LiveConnect statement just seems to freeze the browser.  Can
> LiveConnect be used in this way?
> 
LiveConnect is initially intended for use with applets and webpages, and 
really works in mozilla due to the fact that xul is treated largly as a 
target for rendering (like html). Using it outside of webpages is made 
somewhat harder due to classloading hassles (and I am assuming that as 
you are using nutch you are going to run into classloading and sandbox 
issues).

That said the smile guys at mit have done a lot of work with liveconnect 
and should be able to point you in the right direction.
(http://simile.mit.edu/wiki/Piggy_Bank)

Mozilla Developer Center also has a bunch of documentation here that 
should apply fairly accuratly to what I think you are trying to do
http://developer.mozilla.org/en/docs/Java_in_Firefox_Extensions

However to annoy you live connect is as far as I am aware doomed in 
mozilla 2 to being removed, see here
https://bugzilla.mozilla.org/show_bug.cgi?id=397080
and
http://boomswaggerboom.wordpress.com/2007/04/16/javaplugin-cleanup-for-mozilla-20/
> I would appreciate ANY help anyone can throw at this.
> 
> thanks,
> --Jason