COM/Java Interface
COM/Java IDL
Microsoft Transaction Server

COM/DCOM Overview Part I

Introduction to DCOM

COM/JAVA Interface

by Pat Cichanski

The second resource was the Microsoft Developer Studio Help files.

In order for our ActiveX controls to invoke methods on our Java server, we need a common method of communication.  The means for this communication is COM - which is the Microsoft component model.  COM is a shell that one wraps around components, and that defines how communication is passed between clients and component objects. In effect, we will put a COM wrapper around the Java code we write which will allow non Java code such as Microsoft Visual Basic and ActiveX to interact with the Java code.

The following is the process which is used to convert a Java class to a COM component:

1. Write the Java code so that it can be defined by the IDL (Interface Definition Language). Any data that is to pass between the Java Code and the COM interface must be compatible. For the type equivalents between Java and COM, see COM/Java IDL. Sample Java Code
2. Create the Type Library. An IDL file is intended to be read by humans. The Type Library is actually used by the computer and software such as Visual Basic. The tool used to generate the Type Library from an IDL File is the midl compiler. IDL Sample
3. Register the COM classes. For the Java/COM classes to be used, they must be registered in the system registry. This is where COM will look when trying to find these classes. The tool used for registering classes is javareg.
4. Register the COM classes. For the Java/COM classes to be used, they must be registered in the system registry. This is where COM will look when trying to find these classes. The tool used for registering classes is javareg.
5. This sounds rather complicated and it is! Fortunately, Microsoft seems to be accepting Java as a good idea. The latest version of MS J++ does the above steps automatically. One simply indicates that a class is to be a COM component and the compiler automatically generates the Type Library and registers the COM object in the system registry. Unfortunately, the latest version of J++ is not yet commercial - basically in BETA testing - and also you must purchase the software! Unless you are lucky enough to work for a software company with a subscription to the Microsoft Developers Library! It may be possible to obtain the individual tools mentioned above in the Microsoft Java Software Development Kit which can be downloaded for free. See our reference links for a link to the MS site.
6. And finally, the latest version of MS J++ will also automatically create the dll which can be used by the Microsoft Transaction Server.