Help with JNI

Daniel · #1 (**permalink**) 07-02-2007, 04:37 PM

recently I have seen lots of java articles mentioning JNI.
what is JNI? what is its purposes? how do you use JNI? is the any tutorials on JNI?

Thanks.

Daniel

Eric · #2 (**permalink**) 07-02-2007, 04:41 PM

Ok, well then - JNI is the Java Native Interface. It is a means of using a native (that is, O/S and platform specific) library from within Java. Java and the native library can send data structures back and forth and call methods back and forth. It is most commonly used with C and C++ programs though that is not a requirement.

By definition the use of JNI mean that your code is no longer portable as it isn't 100% Java. You would have to distribute platform specific binaries with your Java just as you would if you coded in C.

A common use is for vendors who don't really want to write in Java and have an already existing native code library. They provide a thin JNI wrapper over the native library and poof - they have Java support.

Greetings.

Eric

Albert · #3 (**permalink**) 07-02-2007, 04:47 PM

A little used, but legitimate use for JNI would be to provide a Java API to hardware.

I have no personal experience to back this up, but it seems to me that with hardware like that it would be in everybody best interest to provide the smallest native lump possible, and then provide as much portable code as possible. Code that comes with a device like that is just overhead, it's not the main order of business. If I were designing the interface for that printer (or something similar), I'd be championing Java. It only makes sense.

Greetings.

Albert