This document discusses using the Java Native Interface (JNI) to allow Java applications to call native code libraries written in C/C++. It explains that JNI allows using existing native libraries, executing time-critical code more efficiently, and accessing native APIs. However, JNI use should be avoided when possible due to complexity in memory management between Java and native code. The document provides an example of defining a native method in Java and implementing it in C/C++ code along with pointers on handling exceptions and memory management across the Java/native boundary.

1. JNI – Java Native Interface
How to persuade my Java application to talk
to evil evil C native code

2. • WHAT?
• WHY?
• WHY NOT?
• THE ACTUAL CODE
• GOODIES

3. Er… WHAT?
Java applications
Native applications

4. But, but…
WHY?

5. But, but…
WHY?
Allows native API function calls

6. But, but…
WHY?
Usage of existing native libraries

7. But, but…
WHY?
Execution of time-critical code

8. OK, so
WHY NOT?
Use of JNI should be avoided
whenever reasonably possible!

9. Example
Java native function declaration first:

10. Example

11. Example

12. Example

13. Example

14. Example

15. Example
Careful!

16. Example

17. Example

18. Example

19. Exceptions?!
Doable but annoying.

20. Other things to know
• Forget about garbage collection
• Java JVM is nazi about its memory space

21. I DON’T EXIST
jernej@virag.si
Skype: izacus