How Can I Integrate Java Functionality into My Existing C Application?

Embedding Java into a C Application

Integrating Java functionality into a pre-existing C application can expand its capabilities. This article explores the possibilities and provides guidance on how to accomplish this goal.

JNI and Java Integration

Java Native Interface (JNI) serves as the bridge between C and Java code. It enables direct access to Java classes and methods from C . However, JNI primarily focuses on Java programs that incorporate C libraries.

C -Java Class Interaction

Your objective is to interact with C classes from within a running Java script. This is possible by embedding a Java Virtual Machine (JVM) into your C application.

JVM Embedding via JNI

JNI provides the necessary tools for embedding a JVM. Here's a simplified example:

<code class="c++">#include <jni.h>

int main() {
  JavaVM *jvm;
  JNIEnv *env;
  JDK1_1InitArgs vm_args;
  vm_args.version = 0x00010001;
  JNI_GetDefaultJavaVMInitArgs(&vm_args);
  JNI_CreateJavaVM(&jvm, &env, &vm_args);
  jclass cls = env->FindClass("Main");
  jmethodID mid = env->GetStaticMethodID(cls, "test", "(I)V");
  env->CallStaticVoidMethod(cls, mid, 100);
  jvm->DestroyJavaVM();
  return 0;
}</jni.h></code>

Sample Java Script

Once the JVM is embedded, you can execute Java scripts similar to the following:

<code class="java">import c4d.documents.*;

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

This script can interact with your C application, in this case, the 3D application Cinema 4D, to remove the selected object.

In summary, embedding a JVM via JNI allows you to integrate Java functionality into your C code, enabling you to extend its capabilities and interact with C classes from within a running Java script.

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