linux jni 之 java 調用c c++

前段時間因為需要，公司需要寫java和c++的程式，把這個分享給大家，當然網上還有更好的，其實jni就是java到C++的資料類型轉換
1.環境
export JAVA_HOME=/opt/java/jdk1.6.0_23
export CLASSPATH=$CLASSPATH:$JAVA_HOME/lib:$JAVA_HOME/jre/lib
export JRE_HOME=$JAVA_HOME/jre

2.：基本操作
   1.java類中聲明本地方法，
   2.然後調用javah命令產生.h標頭檔
   3建立.cpp檔案實現.h裡面產生的方法
   4編譯
   5載入動態庫，調用本地方法

3.貼代碼，為了方便起見我講寫成了makefile檔案 但也有注釋

java類

public class JniDemo{

static {

System.loadLibrary("Demo");
}

public  static native void print();
public  static native int add(int a,int b);

public static void main(String[] args){

print();

System.out.println(add(4,5));

}

JniDemo.h

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

#ifndef _Included_JniDemo
#define _Included_JniDemo
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     JniDemo
 * Method:    print
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_JniDemo_print
  (JNIEnv *, jclass);

/*
 * Class:     JniDemo
 * Method:    add
 * Signature: (II)I
 */
JNIEXPORT jint JNICALL Java_JniDemo_add
  (JNIEnv *, jclass, jint, jint);

#ifdef __cplusplus
}
#endif
#endif
JniDemo.c

#include<stdio.h>
#include <jni.h>
#include "JniDemo.h"

JNIEXPORT void JNICALL Java_JniDemo_print
  (JNIEnv *env, jobject obj){

printf("hello jni kkkkkkkkkkkkkkkkllllllllllllllllllll\n");

}

JNIEXPORT jint JNICALL Java_JniDemo_add
  (JNIEnv *env, jobject obj, jint a, jint b){

return a+b;
}

}

makefile
LD:=ld

CPP:=gcc

CPPFLAGS:=-c
# the libfile name is libDemo.so
LIB:=libDemo.so
#the jni.h path
pathlix:=-I/opt/java/jdk1.6.0_23/include/
pathinclude:=-I/opt/java/jdk1.6.0_23/include/linux

objects:=JniDemo.o

edit:$(objects)
    $(LD) -shared -o $(LIB) $(objects)

JniDemo.o:JniDemo.c JniDemo.h
    $(CPP)  $(pathlix) $(pathinclude) $(CPPFLAGS)  JniDemo.c

clean:
    rm -f $(objects