性能介绍

1. C++启动Java虚拟机

2. 通过C++指针调用main办法

环境

JDK: jdk-17.0.9
mingw-w64: x86_64-8.1.0-release-win32-seh-rt_v6-rev0

实现过程

1. 编写cpp程序

StartJVM.cpp

#include <jni.h>       // JNI header provided by JDK#include <stdio.h>     // C Standard IO Header#include <windows.h>int main() {    JavaVM *jvm;       // Pointer to the JVM (Java Virtual Machine)    JNIEnv *env;       // Pointer to native interface    // JVM initialization arguments    JavaVMInitArgs vm_args;                                 JavaVMOption* options = new JavaVMOption[3];    options[0].optionString = (char*) "-Djava.class.path=D:/SDK/jdk-17.0.9/lib;."; // 设置你的类门路 (classpath)，这里只是一个例子    options[1].optionString = (char*) "-Xmn512m";    options[2].optionString = (char*) "-Xmx1g";    // options[3].optionString = (char*) "-Djava.library.path=D:/SDK/jdk-17.0.9/bin";    vm_args.version = JNI_VERSION_10;             // JVM version. This indicates version 1.6    vm_args.nOptions = 3;    vm_args.options = options;    vm_args.ignoreUnrecognized = JNI_TRUE;        printf("JNI_CreateJavaVM %s\n", options[0].optionString);    HINSTANCE hVM = LoadLibrary("D:\\SDK\\jdk-17.0.9\\bin\\server\\jvm.dll");    if (hVM == NULL) {        printf("Load failed..");    }    typedef jint (CALLBACK *fpCJV)(JavaVM**, void**, JavaVMInitArgs*);    fpCJV CreateJavaVM = (fpCJV)GetProcAddress(hVM, "JNI_CreateJavaVM");    jint rc = CreateJavaVM(&jvm, (void**)&env, &vm_args);    // 加载并初始化一个JVM，"jvm"是返回的JVM接口的指针，"env"是返回的JNI接口的指针       //jint rc = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);      printf("JNI_CreateJavaVM Finished!\n");        if (rc != JNI_OK) {        if (rc == JNI_EVERSION) {            fprintf(stderr, "FATAL ERROR: JVM is oudated and doesn't meet requirements");        }        else if (rc == JNI_ENOMEM) {            fprintf(stderr, "FATAL ERROR: Not enough memory for JVM");        }        else if (rc == JNI_EINVAL) {            fprintf(stderr, "FATAL ERROR: invalid ragument for launching JVM");        }        else if (rc == JNI_EEXIST) {            fprintf(stderr, "FATAL ERROR: the process can only launch one JVM an not multiple");        }        else {            fprintf(stderr, "FATAL ERROR:  unknown error");        }        return rc;    }    else {        printf("JVM load succeeded. Version\n");    }    // 在这里你能够开始调用Java代码 ...    printf("可用调用Java了\n");    /* invoke the Main.test method using the JNI */    jclass cls = env->FindClass("JavaMain");    jmethodID mid = env->GetStaticMethodID(cls, "main", "([Ljava/lang/String;)V");    env->CallStaticVoidMethod(cls, mid, 100);    // 敞开JVM    jvm->DestroyJavaVM();        return 0;}

JavaMain.java

public class JavaMain {    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException {        System.out.println("I'm java");    }}

2. 编译

编译cpp
g++ -Wall -g -I"D:\SDK\jdk-17.0.9\include" -I"D:\SDK\jdk-17.0.9\include\win32" -I"D:\SDK\jdk-17.0.9\include\win32\bridge" -L"D:\SDK\jdk-17.0.9\bin\server" -L"D:\SDK\jdk-17.0.9\bin" -L"D:\SDK\jdk-17.0.9\lib" -ljvm -fPIC StartJVM.cpp -o StartJVM.exe
参数阐明:
-I 指定.h文件门路
-L 指定dll门路
-ljvm 加载jvm.dll
-o 输入门路

将JavaMain也编译到StartJVM.exe同目录， 最终成果

3. 执行StartJVM.exe

双击执行即可

能够看到JVM加载胜利了， 不过执行还有点故障。