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Access a Java Project's class files through a plugin [message #1067595]

Tue, 09 July 2013 13:57

Tobias Freudenreich

Messages: 19
Registered: July 2013

Junior Member

Hi,

I am trying to get access to the class files of a Java Project from a plugin. The idea is that the user writes some Java classes and eventually invokes a handler of my plugin (e.g., through a menu). Furthermore, the user created a config-file in the same project which contains the fully qualified names of some Java classes.

I can read the fully qualified names without any problem in my plugin, now what I would like to do is instantiate the given classes (present in the project) from within my plugin.

I tried using Class.forName() which happens (not much to my surprise). However, I can't seem to come up with working way.

Does anyone know if/how this is possible?

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Re: Access a Java Project's class files through a plugin [message #1067639 is a reply to message #1067595]

Tue, 09 July 2013 18:18

Mark Leone

Messages: 69
Registered: April 2012

Member

What's the problem with using Class.forName()? It's not clear to me from your message.

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Re: Access a Java Project's class files through a plugin [message #1067660 is a reply to message #1067595]

Tue, 09 July 2013 20:31

Thomas Schindl

Messages: 6651
Registered: July 2009

Senior Member

You need to create a custom classloader which includes your projects
classpath.

You can take a look at e(fx)clipse which constructs such a classpath
from the JavaProject definition [1,2].

Tom

[1]http://git.eclipse.org/c/efxclipse/org.eclipse.efxclipse.git/tree/bundles/tooling/org.eclipse.fx.ide.ui.preview/src/org/eclipse/fx/ide/ui/preview/LivePreviewSynchronizer.java#n157
[2]http://git.eclipse.org/c/efxclipse/org.eclipse.efxclipse.git/tree/bundles/tooling/org.eclipse.fx.ide.ui.preview/src/org/eclipse/fx/ide/ui/preview/LivePreviewPart.java#n399

On 09.07.13 15:57, Tobias Freudenreich wrote:
> Hi,
>
> I am trying to get access to the class files of a Java Project from a
> plugin. The idea is that the user writes some Java classes and
> eventually invokes a handler of my plugin (e.g., through a menu).
> Furthermore, the user created a config-file in the same project which
> contains the fully qualified names of some Java classes.
>
> I can read the fully qualified names without any problem in my plugin,
> now what I would like to do is instantiate the given classes (present in
> the project) from within my plugin.
> I tried using Class.forName() which happens (not much to my surprise).
> However, I can't seem to come up with working way.
>
> Does anyone know if/how this is possible?

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Re: Access a Java Project's class files through a plugin [message #1067702 is a reply to message #1067660]

Wed, 10 July 2013 08:10

Tobias Freudenreich

Messages: 19
Registered: July 2013

Junior Member

Mark, the problem with Class.forName is that the project's class file is not accessible for the plugin.

Thomas, thanks for the reply. I'll look into this, even though I was hoping to avoid the issue of creating my own classloader.

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Re: Access a Java Project's class files through a plugin [message #1067710 is a reply to message #1067702]

Wed, 10 July 2013 08:55

Thomas Schindl

Messages: 6651
Registered: July 2009

Senior Member

You have to where from should the running eclipse know about classes you
are just developing in your workspace?

Tom

On 10.07.13 10:10, Tobias Freudenreich wrote:
> Mark, the problem with Class.forName is that the project's class file is
> not accessible for the plugin.
>
> Thomas, thanks for the reply. I'll look into this, even though I was
> hoping to avoid the issue of creating my own classloader.

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Re: Access a Java Project's class files through a plugin [message #1069725 is a reply to message #1067710]

Tue, 16 July 2013 13:02

Tobias Freudenreich

Messages: 19
Registered: July 2013

Junior Member

Tom,
conceptually, I totally know that the running eclipse doesn't have easy access to the classes. However, with all the functionality eclipse provides (content assist, etc.) I was hoping that the infrastructure might provide some kind of API to do exactly that: load classes from a project.
I guess I'll have to walk this on my own.

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Re: Access a Java Project's class files through a plugin [message #1069825 is a reply to message #1069725]

Tue, 16 July 2013 16:38

David Wegener

Messages: 1445
Registered: July 2009

Senior Member

You should consider the implications of loading an unknown class file into a running Eclipse instance. The class can do things that will make Eclipse unstable or even crash. Any static initializers in the class will be run when it is loaded. Dependent classes will attempt to be loaded, bugs in the users code will be executed, etc. If the class can be edited in the running Eclipse instance, you also have the problem of unloading and reloading the class when it is changed. If you really need to deal with user created classes, you should think about launching a separate application instance to test them out.

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