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;
}

javac HelloWorld.java

javah –jni HelloWorld

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class HelloWorld */

#ifndef _Included_HelloWorld
#define _Included_HelloWorld
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class:     HelloWorld
* Method:    displayHelloWorld
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld
(JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

xlc_r –q64 –qarch=auto –qmkshrobj HelloWorld.c –o libhello.so

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!

gcc -I$(JAVA_HOME)/include
-L$(JAVA_HOME)/jre/bin/classic -L$(JAVA_HOME)/jre/bin
-m64 -rdynamic -o invoke invoke.c -ldl –ljvm