COM4J

Interacting with Component Object Model from your Java application.

COM4J Documentations | Releases

Warning

COM4J is not ready for production use. Use at your own risk.

Introduction

Check out Microsoft's own documentation for introduction to Component Object Model.

This library aims to provide COM client functionality for your Java application by using just Foreign Function and Memory API, which means this library have no C++ glue code (yet). It does not support creating COM server at this moment.

Requirement

You must be using Java 23 or newer, since COM4J is using Foreign Memory and Function API. That's also the reason why this repository have zero C++ code!

Quick example

Example 1: Creating new COM object from CLSID

ComFactory com = ComFactory.instance();

// This is CLSID of RealTimeStylus
// Find more of these with https://github.com/jkerai1/CLSID-Lookup
Guid rtsClsid = Guid.of("E26B366D-F998-43ce-836F-CB6D904432B0");
IUnknown rts = com.createFromClsid(IUnknown.class, rtsGuid);

// Since we don't know what to do with RTS (it's pretty useless without extending the interface), we just release it for now.
// Note that you MUST release IUnknown once you are done with it. Java GC will not do it for you.
rts.Release();

Example 2: Creating new COM object from instantiating Java object

// You must use public modifier for your interface and implementation for now
// If you want to create COM object from CLSID, you must provide IID through
// @ComInterface annotation.
// @ComInterface("IID-HERE")
public abstract class IMyComObject extends IUnknown {
	public MyComObject(MemorySegment comPtr, Runnable destroyCallback) {
		super(comPtr, destroyCallback);
	}

	// You must use public modifier for methods annotated with @ComMethod for now
	@ComMethod(index = 3)
	public abstract void coolMethod(int msg);
}

public class MyComObject extends IMyComObject {
	public MyComObject(MemorySegment comPtr, Runnable destroyCallback) {
		super(comPtr, destroyCallback);
	}

	@Override
	public void coolMethod(int msg) {
		System.out.println(msg);
	}
}

ComFactory com = ComFactory.instance();
IMyComObject obj = com.createJava(IMyComObject.class, MyComObject::new);
obj.coolMethod(42);

// Wrap from COM object pointer
IMyComObject wrapped = com.wrap(obj.getComPointer(), IMyComObject.class);
wrapped.coolMethod(727);
wrapped.Release();

// We don't call obj.Release() here because our COM to Java wrapper already
// released it.

Note

You must always release COM object once you are done with it. Java GC will not garbage collect your COM objects.

License

MIT License.

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