vibhatha / jni_playground

jni_playground

Simple Programme

Write a simple HelloWorld class as shown below

class HelloWorld {
    private native void print();
    public static void main(String[] args) {
        new HelloWorld().print();
    }

    static {
        System.loadLibrary("HelloWorld");
    }	
}

Note that the HelloWorld.so is required to be loaded before calling the native method. The native method contains the native keyword and no definition, but the declaration. The definition is in a native library.

Steps to compile

1. javac -h HelloWorld.java, this would generate the class file and the header HelloWorld.h
2. Compile and link

gcc -shared -I${JAVA_HOME}/include -I${JAVA_HOME}/include/linux HelloWorld.c -o libHelloWorld.so

3. Run programme Include the shared library for execution include it in LD_LIBRARY_PATH

   export LD_LIBRARY_PATH=$PWD${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}
   

   and java HelloWorld

   Or,

   run as java -Djava.library.path=. HelloWorld.