有时候我们会想jvm和程序在同一进程中，和jvm交互或者做一些定制工作，需要把jvm嵌入到程序中。简单来说过程可以分为三步：初始化jvm/执行java字节码/退出jvm
初始化jvm
加载libjvm.so到进程中并且调用JNI_CreateJavaVm
JNI_CreateJavaVM(JavaVM **vm, void **penv, JavaVMOption* options)
options我们按照launcher中的设置就好，包含了classpath/command/pid
pid_t pid = getpid();
char *op_pid = NEW_STRING(256);
sprintf(op_pid,"-Dsun.java.launcher.pid=%d",pid);
options[op_count++].optionString = "-Djava.class.path=.";
if(class_path != nullptr && strcmp(class_path,".") != 0){
char *op_class_path = NEW_STRING(strlen(class_path)+50);
sprintf(op_class_path,"-Djava.class.path=%s",class_path);
options[op_count++].optionString = op_class_path;
}
options[op_count++].optionString = "-Dsun.java.command=test_jvm";
options[op_count++].optionString = "-Dsun.java.launcher=SUN_STANDARD";
options[op_count++].optionString = op_pid;
退出jvm
if(vm->DetachCurrentThread() != JNI_OK || vm->DestroyJavaVM() != JNI_OK){
return -1;
}
执行java字节码
JavaVM *vm = init_jvm(".:shen.jar");
JNIEnv *env = get_jni_env();
if(vm == nullptr || env == nullptr)
return -1;
jclass cla = env->FindClass("test");
jmethodID method = env->GetStaticMethodID(cla,"main","([Ljava/lang/String;)V");
jclass cla_string = env->FindClass("java/lang/String");
jobjectArray args = env->NewObjectArray(1,cla_string, nullptr);
char *cwd = NEW_STRING(256);
getcwd(cwd,256);
env->SetObjectArrayElement(args,0,env->NewStringUTF(cwd));
env->CallStaticObjectMethod(cla,method,args);
destroy_jvm();
