Re: XPCOM Component Written in Java

On Jan 26, 5:19 pm, Derrick Rice <[email protected]> wrote:
> On Jan 26, 11:11 am, Derrick Rice <[email protected]> wrote:
>
>
>
> > On Jan 26, 9:41 am, Alberto <[email protected]> wrote:
>
> > > On Jan 23, 11:16 pm, Derrick Rice <[email protected]> wrote:
>
> > > > I've also posted this to the mozswing mailing list, since that's what
> > > > I'm using.  But this seems to be a core XPCOM problem I'm having.
>
> > > > Let me just say that this I am not looking to start a VM from
> > > > mozilla... my entire application is java, with mozilla used via JNI
> > > > (mozswing/JavaXPCOM).  What I want to know is why my components cannot
> > > > be directly access by the javascript, yet they seem to interact in
> > > > other ways.
>
> > > > ------------------------------------------
>
> > > > What is so confusing is that I see the javascript
> > > > successfully interacting with the java, but as soon as I attempt to
> > > > explicitly call a function, it falls.
>
> > > > Goal: Create a new XPCOM component which will be written in Java and
> > > > installed in my mozswing application.  Use it from javascript.
>
> > > > Steps and results:
>
> > > > 1. Create a new interface idl and compile it into an *.xpt and java
> > > > interface. [OK]
> > > > 2. On mozswing initialization, install a factory for this interface
> > > > that will generate java objects.  This is no different than how I've
> > > > installed java factories for other already existing interfaces.[OK]
> > > > 3. After installing the factory, add the component to the "JavaScript
> > > > global property" category, so that it is accessible to website
> > > > javascript. [OK]
> > > > 4. Since the interface extends nsIClassInfo and my component (which I
> > > > generate in the factory) can also queryInterface to
> > > > nsISecurityCheckedComponent, I can allow it to be used from the web
> > > > page.
>
> > > > *** At this point I can successfully create and invoke my component
> > > > through XPCOM with JAVA:
> > > > XPCOMUtils.create("<contract id>", myInterface.class).callFunction()
>
> > > > 5. Generate a test HTML page with javascript that accesses the item
> > > > [This is where things go bad]
>
> > > > var instance = window.myComponent.QueryInterface
> > > > (Components.interface.nsIMyNewInterface);
> > > > alert(instance);             // yields [xpconnect wrapped
> > > > nsIMyNewInterface]
> > > > alert(instance.member);           // yields the value of the member
> > > > alert(instance.callFunction);             // yields function
> > > > callFunction() { [native code] }
> > > > instance.callFunction();        // generates an error, see below
>
> > > > [Exception... "Component returned failure code: 0x80004001
> > > > (NS_ERROR_NOT_IMPLEMENTED) [nsIMyNewInterface.callFunction]"
> > > > nsresult: "0x80004001 (NS_ERROR_NOT_IMPLEMENTED)"  location: "JS frame
> > > > :: webpage.html :: run :: line 15"  data: no]
>
> > > > If I throw print statements into my java component, I see it being
> > > > access (QueryInterface is called and so are the
> > > > nsISecurityCheckedComponent functions).  This indicates to me that
> > > > it's clearly possible for the javascript to communicate with the java.
> > > >  It's already taking place when I call QueryInterface.  But if I try
> > > > to call something else, it fails.
>
> > > > Am I running into a natural limitation of JavaXPCOM?  How can I
> > > > communicate back to my existing java application from javascript
> > > > XPCOM?
>
> > > > Problems solved:
> > > > * accessing XPCOM from javascript
> > > > * installing XPCOM factories from java
> > > > * making components visible and accessible to webpages
>
> > > > Problems existing:
> > > > * using my components from javascript
>
> > > > I saw someone else had this problem but saw no solution:http://osdir.com/ml/mozilla.devel.java/2006-01/msg00007.html
>
> > > > Again, any help here would be seriously appreciated.  Even if it's
> > > > just a little insight.
>
> > > Even if i'm some step behind you i guess I could probably help you.
> > > I succeded (from java,not javascript yet) to register the XPcom object
> > > created implementing the interface and to access its method.
> > > What I'm still not able to do is register the XPcom object
> > > independently from running the java code,either in a dynamic way or in
> > > a static one.
> > > Since I guess you succeeded in doing that can you help me out?
> > > Thanks in advance
>
> > I don't know if I 100% understand your question, but I'll give 2
> > answers, because I think 1 of them might be what you're looking for.
>
> > 1) If your intention is to run mozilla embedded in a java application,
> > then you can register the java component in java code.  It sounds like
> > this is what you've been able to do.  This is done by installing a
> > factory.  This is my mozswing code... I don't know if any of it is
> > specific to mozswing or is just javaxpcom (which mozswing is built on
> > top of)
>
> > ObjectFactory factory = new ObjectFactory(); // implements nsIFactory
> > XPCOMUtils.register(myContractID, factory);  // this calls
> > nsIComponentRegistrar.registerFactory for me
>
> > 2) What it sounds like you want to do, though, is register a java
> > component without having to originally run mozilla in java.  That is
> > "independently" from java, as you put it.  My understanding is that to
> > do this, you need to use LiveConnect[1].  Read this page about 'Java
> > in Firefox Extensions' [2].
>
> > The difference is that in 2) I don't think you have a single JVM.  I
> > think a JVM is created on demand and kept open for your extension.
> > Other extensions might not use the same JVM.  And if you ran mozilla
> > embedded in Java, you would probably still create a new JVM.  Not at
> > all what I'm after.
>
> > [1]https://developer.mozilla.org/en/LiveConnect
> > [2]https://developer.mozilla.org/en/Java_in_Firefox_Extensions
>
> > For reference, what I followed was the instructions in these 3 posts,
> > but adapted it for Java.
>
> > "Exposing XPCOM Components in Javascript"http://weblogs.mozillazine.org/weirdal/archives/017188.htmlhttp://web...
>
> > If I didn't answer your question, please do clarify and I'll try to
> > help.
>
> and for clarity, I can do the following:
>
> * write an xpcom component in java, and access it from java
> * write an xpcom component in javascript, and access it from
> javascript
> * write an xpcom component in javascript, and access it from java
>
> I CANNOT
>
> * write an xpcom component in java, and access it from javascript.

This answer perfectly to what I was looking for. I red a lot of post
about javaXpcom but in no one of them I could find an answer to the
question if was already possible to write an xpcom component in java
following the same procedure you would follow writing it either in c++
or javascript.
I guess this is not possible yet,so i'll take a look to the
liveconnect strategy.
Thanks a lot to sort my doubts out.