将Java嵌入到C ++应用程序中？ [英] Embed Java into a C++ application?

问题描述

我有一个用C ++编写的应用程序，我可以通过在C ++中编写插件来扩展应用程序的功能。

我基本上想做的是将Java嵌入到此应用程序中。这已经用Python完成了（不是我做的）。

我读了一些关于JNI的东西，但总是有一个完整的程序使用Java类的演讲。 / p>

我想做的是使用C ++中的类来与应用程序交互。

这是一个3D应用程序，称为Cinema 4D。

有没有办法在应用程序运行时（使用某种脚本语言）使用JNI或类似的东西来编译和评估Java代码？

嵌入完成后的假想代码示例：

  import c4d .documents。*; 
 
 class Main {
 public static void main（）{
 BaseDocument doc = GetActiveDocument（）; 
 BaseObject op = doc.GetActiveObject（）; 
 if（op！= null）{
 op.Remove（）; 
} 
} 
} 
  

此代码应与Cinema 4D删除所选对象。

解决方案

您可以在应用程序中嵌入JVM。 Oracle的官方参考书有一些详细信息。它的概要是：

  #include< jni.h> / *其中一切都被定义* / 
 
 int main（）{
 JavaVM * jvm; / *表示Java VM * / 
 JNIEnv * env; / *指向本地方法接口的指针* / 
 JDK1_1InitArgs vm_args; / * JDK 1.1 VM初始化参数* / 
 vm_args.version = 0x00010001; / * 1.1.2新增：VM版本* / 
 / *获取默认初始化参数并设置类
 * path * / 
 JNI_GetDefaultJavaVMInitArgs（& vm_args）; 
 vm_args.classpath = ...; 
 / *加载并初始化Java VM，在env * / 
中返回JNI接口
 *指针JNI_CreateJavaVM（& jvm，& env，& vm_args）; 
 / *使用JNI调用Main.test方法* / 
 jclass cls = env-> FindClass（Main）; 
 jmethodID mid = env-> GetStaticMethodID（cls，test，（I）V）; 
 env-> CallStaticVoidMethod（cls，mid，100）; 
 / *我们可以创建一个对象，并调用它的方法* / 
 / *我们完成了。 * / 
 jvm-> DestroyJavaVM（）; 
} 
  

你想要的（例如自定义类加载器），但这是关于它在您的应用程序中获得JVM工作所需的最低需求。

I got an application written in C++ and I am able to extend the applications functionality by writing plugins in C++ for it.

What I basically want to do is to embed Java into this application. This has already been done with Python (not done by me).

I read something about JNI but there is always the speech from a full programm that uses Java classes.

What I'd like to do is, to use classes from C++ in Java to interact with the application.
It's a 3D app in this case, called Cinema 4D.

Is there a way to compile and evaluate Java code while the application is running (in some sort of scripting language) using JNI or anything like it ?

Example imaginary code after the embedding was done:

import c4d.documents.*;

class Main {
  public static void main() {
    BaseDocument doc = GetActiveDocument();
    BaseObject op = doc.GetActiveObject();
    if (op != null) {
      op.Remove();
    }
  }
}

This code should interact with Cinema 4D to delete the selected object.

解决方案

You can embed a JVM within your application. Oracle's official reference book has some more details. The synopsis of it is:

#include <jni.h>       /* where everything is defined */

int main() {
  JavaVM *jvm;       /* denotes a Java VM */
  JNIEnv *env;       /* pointer to native method interface */
  JDK1_1InitArgs vm_args; /* JDK 1.1 VM initialization arguments */
  vm_args.version = 0x00010001; /* New in 1.1.2: VM version */
  /* Get the default initialization arguments and set the class 
   * path */
  JNI_GetDefaultJavaVMInitArgs(&vm_args);
  vm_args.classpath = ...;
  /* load and initialize a Java VM, return a JNI interface 
   * pointer in env */
  JNI_CreateJavaVM(&jvm, &env, &vm_args);
  /* invoke the Main.test method using the JNI */
  jclass cls = env->FindClass("Main");
  jmethodID mid = env->GetStaticMethodID(cls, "test", "(I)V");
  env->CallStaticVoidMethod(cls, mid, 100);
  /* We could have created an Object and called methods on it instead */
  /* We are done. */
  jvm->DestroyJavaVM();
}

You can do far more sophisticated things if you want (e.g. custom class loaders) but that's about it in terms of the bare minimum needed to get a JVM working within your application.

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