3.通过JNI加载java虚拟机

        前面已经分析了java命令加载java虚拟机的方法，即通过JNI和虚拟机交互。因此我们可以很容易的自己写相应的启动代码，实现在C++程序中执行java程序，调用java类的方法。
     要测试的Java类(Test.java)的代码是：
public class Test {
public Test(){
System.out.println("Test's constructor");
}
public void sayHello(){
System.out.println("Test object say : Hello!");
}
public static int add(int arg1,int arg2){
return arg1 + arg2;
}

public static void main(String[] args) {
for (int i = 0; i < args.length; i++) {
System.out.println(args[i]);
}
}
}

 
   加载jvm的C++(StartJVM.cpp)代码如下：
/*
* startjvm.cpp
*
* Created on: 2010-1-28
* Author: Xiutao Zang
*/
#include <iostream>
#include <jni.h>
using namespace std;
int main()
{
JavaVMOption options[1];
options[0].optionString = "-Djava.class.path=.";
JavaVMInitArgs args;
memset(&args, 0, sizeof(args));
args.version = JNI_VERSION_1_2;
args.nOptions = 1;
args.options = options;
args.ignoreUnrecognized = JNI_FALSE;
JNIEnv *env = 0;
JavaVM *vm = 0;
jint result = JNI_CreateJavaVM(&vm, (void **)&env, &args);
if (result == JNI_OK)
{
cout << "create the jvm successfully!" << endl;
jclass mainClass = env->FindClass("Test");
if (mainClass != 0)
{
cout << "find the main class successfully!" << endl;
jclass stringClass = env->FindClass("java/lang/String");
enum
{
LENGTH = 2
};
const char *mainParams[LENGTH] = { "Hello ", "World!" };
jstring jstringTemp;
jobjectArray mainArgs = env->NewObjectArray(LENGTH, stringClass, 0);
for (int i = 0; i < LENGTH; i++)
{
jstringTemp = env->NewStringUTF(mainParams[i]);
env->SetObjectArrayElement(mainArgs, i, jstringTemp);
}
jmethodID mainID