access native(existing) dll's from java

otherwise ;)
use ms.* microsoft java packages

I would _really_ recommend reading the JNI thread of the Java Tutorial. It is free and can be read online or downloaded. This will give you a decent overview. If you need more info, I'd suggest buying either the Addison-Wesley JNI Programmer's Guide or Essential JNI (can't remember the publisher).

To get you started, here is an extremely simplified explanation of what you need to do for JNI access to an existing dll.

First, write a Java class encapsulating the access from the Java side. This class will declare one or more native methods and (likely) have a static initialization block to load the library:

    // you can put it in any package you want
    package util.native;
    public class NativeAccess {
        public native char[] doSomething(char[]);

        static {
            System.loadLibrary("native.dll");
        }
    }

Compile the class. Run javah to produce a C/C++ header file. In this case, if you run it correctly, javah will produce util_native_NativeAccess.h.

Now write your C or C++ file to implement this native method.

    #include "util_native_NativeAccess.h"
    JNIEXPORT jcharArray JNICALL Java_util_native_NativeAccess_doSomething(
JNIEnv *env,
jobject java_this,
jcharArray param) {
    // method implementation
}

Now compile the native code as a shared library, put it in a directory named by your PATH variable, and you are ready to run.

There are special rules for using java arrays in native code. The Java Tutorial briefly addresses this and provides some sample code. I know its all a little confusing at first. Find some samples (in the tutorial, the books, or from searching the web) and study them. IMHO, this is the best way to see how it all fits together.

Best regards,
Jim Cakalic

as i said, i need to use an EXISTING dll, i dont need new native code