李岩--JNI实现c++于java代码相互调用过程

JNI实现c++于java代码相互调用过程---李岩

1.在D盘新建HelloWorld文件夹，文件夹中两个文件。如下

HelloWorld.java
________________________________________

import java.util.Date;
public class HelloWorld {
    public native void print();
public native void test(int i,String str1,String str2,int[] arr);
public int property=888;
public int function(int foo,Date date,int[] arr)
{
   System.out.println("print in function()");
   return 0;
}

    public static void main(String[] args) {
HelloWorld hw=new HelloWorld();
hw.print();
int[] arr={5,6,7,8,9,0};
hw.test(222,"string in java1","string in java2",arr);
    }
    static {
        System.loadLibrary("HelloWorld");
    }
}
____________________________________________
        HelloWorld.cpp
______________________________________________

#include <jni.h>
#include <stdio.h>
#include "HelloWorld.h"
#include <iostream>
using namespace std;

JNIEXPORT void JNICALL
Java_HelloWorld_print(JNIEnv *env, jobject obj)
{
//*********java调用c++中的函数*********
   cout<<"heoo"<<endl;
cout<<"liyan "<<endl;
//*********C++?调用java中function（）并传值给java function（）***********
jclass hello_class=env->GetObjectClass( obj);//getclass
jfieldID fieldID_prop = env ->GetFieldID(hello_class,"property","I");//get fieldid
jmethodID methodID_function=env->GetMethodID(hello_class,"function","(ILjava/util/Date;[I)I");//get methodId
env->CallIntMethod(obj,methodID_function,0L,NULL,NULL );//ivoke method
jint property=env->GetIntField(obj,fieldID_prop);//get field's vlaue;
cout<<"get proterty in java code is :"<<property<<endl;
env->SetIntField(obj,fieldID_prop,999L);//set property in java
jint property_beModify=env->GetIntField(obj,fieldID_prop);//get field's vlaue;
cout<<"modify property in java by C++ is :"<<property_beModify<<endl;

//******************************************
    return;
}

JNIEXPORT void JNICALL
Java_HelloWorld_test(JNIEnv * env, jobject obj, jint i, jstring str1,jstring str2,jintArray arr)
{
//*********get argument form java code********************
cout<<i<<endl;//get int value
cout<<"test()"<<endl;
const char* szStr1=env->GetStringUTFChars(str1,JNI_FALSE); //get string class
cout<<szStr1<<endl;
const char* szStr2=env->GetStringUTFChars(str2,JNI_FALSE); //get string class
cout<<szStr2<<endl;
env->ReleaseStringUTFChars(str1,szStr1); //release resourse
env->ReleaseStringUTFChars(str2,szStr2); //release resourse
//*****get array from java********************
jint* arr_inc = env->GetIntArrayElements(arr,JNI_FALSE);
jint number=env->GetArrayLength(arr);
for(int j=0;j<number;j++)
{
   cout<<arr_inc[j]<<endl;
}
env->ReleaseIntArrayElements(arr,arr_inc,JNI_FALSE);

}

2.运行cmd，进入windows命令行。进入D：\HelloWorld文件夹

        d:
        cd HelloWorld

3.编译java

      javac HelloWorld.java

4.为HelloWorld.cpp编译头文件

     javah -jni HelloWorld

5.编译C++成dll文件

    cl -I%java_home%\include -I%java_home%\include\win32 -LD HelloWorld.cpp -FeHelloWorld.dll

6.设置windows的环境变量

    把D:\HelloWorld 加入的windows的环境变量

7.运行java class

    java HelloWorld

8.显示出如下

heoo
liyan
print in function()
get proterty in java code is :888
modify property in java by C++ is :999
222
test()
string in java1
string in java2
5
6
7
8
9
0

如有疑问或所要代码可联系我李岩

MSN: savagert@163.com
Email: savagert@163.com

李岩

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