java 与 C 互相调用

LINUX 下的 java 与 C++ 互相调用

Hello.java

public class Hello 
{ 
        static 
        {   
                try 
                {   
                        // 此处即为本地方法所在链接库名
                            
                        System.loadLibrary("hello"); 
                }   
                catch(UnsatisfiedLinkError e)  
                {   
                        System.err.println( "Cannot load hello library:\n " + 
                                        e.toString() );  
                }   
        }   
        public Hello() 
        {   
        }   
        // 声明的本地方法
        public native void SayHello(String strName); 

        public static void main(String[] args){
                System.out.println("1111111");

        }   
        public  void print(){

                System.out.println("native call java");
        }   
}

javac Hello.java ; javah Hello.java

产生Hello.h

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

#ifndef _Included_Hello
#define _Included_Hello
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     Hello
 * Method:    SayHello
 * Signature: (Ljava/lang/String;)V
 */
JNIEXPORT void JNICALL Java_Hello_SayHello
  (JNIEnv *, jobject, jstring);

#ifdef __cplusplus
}
#endif
#endif

编写Hello.cpp

#include "Hello.h"
#include <stdio.h> 
// 与 Hello.h 中函数声明相同
JNIEXPORT void JNICALL Java_Hello_SayHello  (JNIEnv * env, jobject arg, jstring instring) 
{ 
        // 从 instring 字符串取得指向字符串 UTF 编码的指针
        const jbyte *str = 
                (const jbyte *)env->GetStringUTFChars( instring, JNI_FALSE );  
        printf("Hello,%s\n",str); 
        //调用java代码 
        try{
                jclass cls = env->GetObjectClass(arg);
                jmethodID print= env->GetMethodID(cls,"print","()V");
                env->CallIntMethod(arg,print);
        }catch(int){
                printf("ERRRR");


        }   

        return; 
}

编译

#!/bin/bash
export LD_LIBRARY_PATH='~/c/jni/':$LD_LIBRARY_PATH
echo "g++ -I/home/huaonline/libs/jdk/include   -I/home/huaonline/libs/jdk/include/linux -fPIC -c Hello.cpp"
g++ -I/home/huaonline/libs/jdk/include   -I/home/huaonline/libs/jdk/include/linux -fPIC -c Hello.cpp
echo "g++ -shared -Wl,-soname,libhello.so.1 -o libhello.so.1.0 Hello.o"
g++ -shared -Wl,-soname,libhello.so.1 -o libhello.so.1.0 Hello.o
echo "cp libhello.so.1.0 libhello.so"
cp libhello.so.1.0 libhello.so
java ToSay

结果

g++ -I/home/huaonline/libs/jdk/include   -I/home/huaonline/libs/jdk/include/linux -fPIC -c Hello.cpp
g++ -shared -Wl,-soname,libhello.so.1 -o libhello.so.1.0 Hello.o
cp libhello.so.1.0 libhello.so
Hello,John
native call java