实际项目中C++如何调用java应用

liangjz

今天看阿里巴巴搜索技术中心文档，无意发现：

“camera内部是采用java语言来实现的，本接口把camera的java接口封装成C++接口，通过c语言构建jvm来调用camera的java接口”，

我就很想一看究竟c++如何调用java程序了。



参考http://www.velocityreviews.com/f ... ll-java-from-c.html





D:\lr_script\MyJNI>java -version

java version "1.5.0_06"



DemoMain.java内容如：

import java.io.*;

public class DemoMain {

public static void main(String[] args) throws java.io.IOException, java.lang.NullPointerException

{

System.out.println("This is a test.");

}// end main().

}// end class DemoMain.



采用vc6++ IDE，采用JNI技术实现。

（1）    编译时:

C++  preprocessor->additional include directories:

  加入 D:\Sun\AppServer\jdk\include

（2）运行时,

把 D:\Sun\AppServer\jdk\jre\bin\server\jvm.dll 加入环境变量。



#ifndef __cplusplus

#define __cplusplus

#endif

#include "jni.h"

#include <stdio.h>

#include <stdlib.h>

#include <windows.h>

#pragma comment (lib,"D:\\Sun\\AppServer\\jdk\\lib\\jvm.lib")



void main() {



JavaVM *jvm;

JNIEnv *env;



JavaVMInitArgs vm_args;

JavaVMOption options[3];



options[0].optionString = "-Djava.compiler=NONE";

options[1].optionString = "-Djava.classpath=.";

options[2].optionString = "-verbose:jni";



vm_args.version = JNI_VERSION_1_4;

vm_args.nOptions = 3;

vm_args.options = options;

vm_args.ignoreUnrecognized = JNI_TRUE;



jint res = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);

if (res < 0) {

fprintf(stderr, "Can't create Java VM\n");

exit(1);

};



jclass cls = env->FindClass("DemoMain");

if (cls == 0) printf("Sorry, I can't find the class");



fprintf(stdout, "This is invokeSimplified4.\n");



jmethodID get_main_id;



if(cls != NULL)

{



get_main_id =env->GetStaticMethodID(cls,"main","([Ljava/lang/String;)V");



fprintf(stdout, "This is invokeSimplified5.\n");



if(get_main_id != NULL )

{

      jclass string = env->FindClass("java/lang/String");

      jobjectArray args = env->NewObjectArray(0,string, NULL);



      fprintf(stdout, "This is invokeSimplified6.\n");

      int i = env->CallIntMethod(cls, get_main_id, args);

      fprintf(stdout, i+ "This is invokeSimplified7.\n");

}

}// end IF.



jvm->DestroyJavaVM();

fprintf(stdout, "Java VM destory\n");

}//end main.