Linux on POWER 的 JNI 编程实例

                    
class HelloWorld {
   /* Native method declaration */
   public native void displayHelloWorld();
     /* Use static intializer */
      static {
         System.loadLibrary("hello");
      }
      /* Main function calls native method*/
      public static void main(String[] args) {
        new HelloWorld().displayHelloWorld();
      }
}

                    
#include <jni.h>
#include "HelloWorld.h"
#include <stdio.h>
JNIEXPORT void JNICALL
Java_HelloWorld_displayHelloWorld(JNIEnv *env, jobject obj)
{
    printf("Hello world!\n");
    return;
}

java –cp . HelloWorld

HelloWorld!

                
#include <jni.h>
#include "HelloWorld.h"
#include stdio.h>
extern void func1(), func2(),func3();
JNIEXPORT void JNICALL
Java_HelloWorld_displayHelloWorld(JNIEnv *env, jobject obj)
{
    printf("Hello world!\n");
    func1();
    func2();
    func3();
    return;
}

                
/************
* share1.c: *
*************/
#include <stdio.h>
void func1()
{
   printf("func1 called\n");
}
void func2()
{
   printf("func2 called\n");
}

                
/************
* share2.c  *
*************/
void func3 ()
 {
   printf("func3 called\n");
 }

                
# This definition makes JAVA_HOME refer to the JDK specified in your PATH.
# You can change this to refer to a specific directory
JAVA_HOME=/opt/IBMJava2-ppc64-142
libhello.so: shrsub.o HelloWorld.h
        xlc_r -M -I. -I$(JAVA_HOME)/include  -q64 -qarch=auto -
        qmkshrobj HelloWorld.c shrsub.o -o libhello.so
HelloWorld.h: HelloWorld.class
        $(JAVA_HOME)/bin/javah -jni HelloWorld
HelloWorld.class:
        $(JAVA_HOME)/bin/javac  HelloWorld.java
shrsub.o: c.o
        xlc_r -qmkshrobj -q64 -o shrsub.o share1.o share2.o
c.o:
        xlc_r -q64 -c share1.c
        xlc_r -q64 -c share2.c

 java –cp . HelloWorld

Hello world!
func1 called
func2 called
func3 called

                
#include <jni.h>
#include <stdlib.h>
#include <iostream.h>
int main() {
    JNIEnv *env;
    JavaVM *jvm;
    JavaVMInitArgs vm_args;
    JavaVMOption options[5];
    jint res;
    jclass cls;
    jmethodID mid;
    jstring jstr;
    jobjectArray args;
     options[0].optionString = "-Xms4M";
     options[1].optionString = "-Xmx64M";
     options[2].optionString = "-Xss512K";
     options[3].optionString = "-Xoss400K";
     options[4].optionString = "-Djava.class.path=.";
     vm_args.version = JNI_VERSION_1_4;
     vm_args.options = options;
     vm_args.nOptions = 5;
     vm_args.ignoreUnrecognized = JNI_FALSE;
    /* Create the Java VM */
    res = JNI_CreateJavaVM(&jvm,(void**)&env,&vm_args);
    if (res < 0) {
        cerr<< "Can't create Java VM" << endl;
        goto destroy;
    }
    cls = env->FindClass("Prog");
    if (cls == 0) {
        cerr << "Can't find Prog class" << endl;
        goto destroy;
    }
    mid = env->GetStaticMethodID(cls, "main", "([Ljava/lang/String;)V");
    if (mid == 0) {
        cerr<< "Can't find Prog.main" << endl;
        goto destroy;
    }
    jstr = env->NewStringUTF(" from C++!");
    if (jstr == 0) {
        cerr << "Out of memory" << endl;
        goto destroy;
    }
    args = env->NewObjectArray( 1,
                        env->FindClass("java/lang/String"), jstr);
    if (args == 0) {
        cerr << "Out of memory" << endl;
        goto destroy;
    }
    env->CallStaticVoidMethod( cls, mid, args);
destroy:
    if (env->ExceptionOccurred()) {
       env->ExceptionDescribe();
    }
    jvm->DestroyJavaVM();
}

                
public class Prog {
        public static void main(String[] args) {
               System.out.println("Hello World" + args[0]);
        }
}

                
# This definition makes JAVA_HOME refer to the JDK specified in your PATH.
# You can change this to refer to a specific directory
JAVA_HOME=/opt/IBMJava2-ppc64-142
all:    invoke Prog.class
invoke:
        xlC -q64 -I$(JAVA_HOME)/include –
        L$(JAVA_HOME)/jre/bin/classic -L$(JAVA_HOME)/jre/bin -ljvm -o
         invoke invoke.cpp
Prog.class:
        $(JAVA_HOME)/bin/javac Prog.java
clean:
        rm -f *.class invoke *.o

./invoke

Hello World from C++!

                
#include <jni.h>
#include <stdlib.h>
#include <dlfcn.h>
main() {
    JNIEnv *env;
    JavaVM *jvm;
    JavaVMInitArgs vm_args;
    JavaVMOption options[5];
    jint res;
    jclass cls;
    jmethodID mid;
    jstring jstr;
    jobjectArray args;
    char classpath[1024];
    vm_args.version = 0x00010004;
    vm_args.options = options;
    vm_args.nOptions = 5;
    vm_args.ignoreUnrecognized = JNI_FALSE;
    options[0].optionString = "-Xms4M";
    options[1].optionString = "-Xmx64M";
    options[2].optionString = "-Xss512K";
    options[3].optionString = "-Xoss400K";
    options[4].optionString = "-Djava.class.path=.";
    void* lib_handle = 0;
    void* (*lib_func)() = 0;
    lib_handle = dlopen("/opt/IBMJava2-ppc64-
    142/jre/bin/classic/libjvm.so", RTLD_NOW);
    if (!lib_handle)
    {
       fprintf(stderr, "dlopen failed\n");
       goto destroy;
    }
    lib_func = (void*(*)())dlsym(lib_handle, 
    "JNI_GetDefaultJavaVMInitArgs");
    lib_func(&vm_args);
    lib_func = (void*(*)())dlsym(lib_handle, "JNI_CreateJavaVM");
    lib_func(&jvm,&env,&vm_args);
    cls = (*env)->FindClass(env, "Prog");
    if (cls == 0) {
        fprintf(stderr, "Can't find Prog class\n");
        goto destroy;
    }
    mid = (*env)->GetStaticMethodID(env, cls, "main", 
    "([Ljava/lang/String;)V");
    if (mid == 0) {
        fprintf(stderr, "Can't find Prog.main\n");
        goto destroy;
    }
    jstr = (*env)->NewStringUTF(env, " from C!");
    if (jstr == 0) {
        fprintf(stderr, "Out of memory\n");
        goto destroy;
    }
    args = (*env)->NewObjectArray(env, 1,
                        (*env)->FindClass(env, "java/lang/String"), jstr);
    if (args == 0) {
        fprintf(stderr, "Out of memory\n");
        goto destroy;
    }
    (*env)->CallStaticVoidMethod(env, cls, mid, args);
    destroy:
    if ((*env)->ExceptionOccurred(env)) {
         (*env)->ExceptionDescribe(env);
    }
    (*jvm)->DestroyJavaVM(jvm);
}

                
# This definition makes JAVA_HOME refer to the JDK specified in your PATH.
# You can change this to refer to a specific directory
JAVA_HOME=/opt/IBMJava2-ppc64-142
all:    invoke Prog.class
invoke:
        xlc -I$(JAVA_HOME)/include -L$(JAVA_HOME)/jre/bin/classic 
       -L$(JAVA_HOME)/jre/bin -q64 -qarch=auto -o invoke invoke.c -ljvm
Prog.class:
       $(JAVA_HOME)/bin/javac Prog.java
clean:
        rm -f *.class invoke *.o

./invoke

Hello World from C!