C/C++启动JVM

C/C++启动JVM

• 测试环境
• 目录结构
• 需要的资源文件路径
• • jni.h
  • jni_md.h
  • jre
• 代码
• 项目下载

测试环境

系统:windwos 10
架构:x86_64
开发工具:Visual Studio 2019
java:1.8

目录结构

需要的资源文件路径

jni.h 头文件在  jdk/include/jin.h
jni_md.h 头文件在 jdk/include/win32/jni_md.h

jre 即java运行环境jvm在 jdk/jre

jni.h

jni_md.h

jre

代码

#include "windows.h"
#include "iostream"
#include <tchar.h>
#include "jni.h"
#include <libloaderapi.h>

using namespace std;

typedef jint(JNICALL* JNICREATEPROC)(JavaVM**, void**, void*);

bool startJVM();

int _tmain(int argc, _TCHAR* argv[])
{
	cout << "Application run." << endl;
	startJVM();
	return 0;
}

//启动java虚拟机
bool startJVM() {
	int pause;
	//获取jvm动态库的路径
	TCHAR* jvmPath = _T(".\\jre\\bin\\server\\jvm.dll");

	//java虚拟机启动时接收的参数，每个参数单独一项
	int nOptionCount = 2;
	JavaVMOption vmOption[2];
	//设置JVM最大允许分配的堆内存，按需分配
	vmOption[0].optionString = "-Xmx1024M";
	//设置classpath
	vmOption[1].optionString = "-Djava.class.path=./Test.jar";

	JavaVMInitArgs vmInitArgs;
	vmInitArgs.version = JNI_VERSION_1_8;
	vmInitArgs.options = vmOption;
	vmInitArgs.nOptions = nOptionCount;
	//忽略无法识别jvm的情况
	vmInitArgs.ignoreUnrecognized = JNI_TRUE;

	//设置启动类，注意分隔符为"/"
	const char startClass[] = "test/Test";
	//启动方法，一般是main函数，当然可以设置成其他函数
	const char startMethod[] = "main";

	//加载JVM,注意需要传入的字符串为LPCWSTR,指向一个常量Unicode字符串的32位指针，相当于const wchar_t*
	HINSTANCE jvmDLL = LoadLibrary(jvmPath);
	if (jvmDLL == NULL) {
		cout << "加载JVM动态库错误" << endl;
		return false;
	}

	//初始化jvm物理地址
	JNICREATEPROC jvmProcAddress = (JNICREATEPROC)GetProcAddress(jvmDLL, "JNI_CreateJavaVM");
	if (jvmDLL == NULL) {
		FreeLibrary(jvmDLL);
		cout << "加载JVM动态库错误" << endl;
		return false;
	}

	//创建JVM
	JNIEnv* env;
	JavaVM* jvm;
	jint jvmProc = (jvmProcAddress)(&jvm, (void**)&env, &vmInitArgs);
	if (jvmProc < 0 || jvm == NULL || env == NULL) {
		FreeLibrary(jvmDLL);
		cout << "创建JVM错误" << endl;
		return false;
	}

	//加载启动类
	jclass mainclass = env->FindClass(startClass);
	if (env->ExceptionCheck() == JNI_TRUE || mainclass == NULL) {
		env->ExceptionDescribe();
		env->ExceptionClear();
		FreeLibrary(jvmDLL);
		cout << "加载启动类失败" << endl;
		return false;
	}

	//加载启动方法
	jmethodID methedID = env->GetStaticMethodID(mainclass, startMethod, "([Ljava/lang/String;)V");
	if (env->ExceptionCheck() == JNI_TRUE || methedID == NULL) {
		env->ExceptionDescribe();
		env->ExceptionClear();
		FreeLibrary(jvmDLL);
		cout << "加载启动方法失败" << endl;
		cin >> pause;
		return false;
	}

	cout << "开始执行" << endl;
	env->CallStaticVoidMethod(mainclass, methedID, NULL);
	cout << "执行结束" << endl;

	//jvm释放
	jvm->DestroyJavaVM();
	return true;
}

项目下载

CSDN下载