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At the time of this writing, Microsoft does not support JNI, but provides proprietary support to call non-Java code. This support is built into the compiler, the Microsoft JVM, and external tools. The features described in this section will work only if your program was compiled using the Microsoft Java compiler and run on the Microsoft Java Virtual Machine. If you plan to distribute your application on the Internet, or if your Intranet is built on different platforms, this can be a serious issue.
The Microsoft interface to Win32 code provides three ways to connect to Win32:
- J/Direct: A way to easily call Win32 DLL functions, with some limitations.
- Raw Native Interface (RNI) : You can call Win32 DLL functions, but you must then handle garbage collection.
- Java/COM integration : You can expose or call COM services directly from Java.
I’ll cover all three techniques in the following sections.
At the time of writing, these features were tested on the Microsoft SDK for Java 2.0 beta 2, which was downloaded (with a painful process they call “Active Setup”) from the Microsoft Web site. The Java SDK is a set of command-line tools, but the compilation engine can be easily plugged into the Developer Studio environment, allowing you to use Visual J++ 1.1 to compile Java 1.1 code.