JNI Tutorial 2

Hello.cpp

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <jni.h>

int main (int argc, char *argv[])
{
        JavaVM *jvm;                    /* 宣告一個java machine */
        JNIEnv *env;                    /* JNI的環境 */
        JavaVMInitArgs vm_args;

        /*自定義JRE所要的參數，就是java -... -... xxx.java將-...字串加入options中 用*/
        JavaVMOption options[1];

        jint res;
        jclass cls;
        jmethodID mid;


        vm_args.version = JNI_VERSION_1_6;  /*使用的版本*/
        options[0].optionString = "-Djava.class.path=./";
        vm_args.nOptions = 1;
        vm_args.options = options;
        vm_args.ignoreUnrecognized = JNI_FALSE;

        /*產生一個java machine*/
        res = JNI_CreateJavaVM(&jvm,(void**)&env,&vm_args);

        jclass ver;
        jmethodID print;

        /*找Helloworld Class*/
        cls = env->FindClass("HelloWorld");  

        if (cls == 0) printf("cls error \n");

        /*>確定要執行的 function是甚麼 
           在這裡指的是HelloWorld裡的main 
           後面是main要傳的參數*/
        mid = env->GetStaticMethodID(cls, "main", "([Ljava/lang/String;)V"); 

        if (mid == 0) printf("mid error \n");

        env->CallStaticVoidMethod(cls, mid); /*執行此class*/

        printf("Hello in c\n");
        return 0;
}

HelloWorld.java

public class HelloWorld {
        public static void main(String[] args) {
                System.out.println("Hello, World in Java");
        }
}