从 Java 调用 C++ dll [英] Calling C++ dll from Java

问题描述

我将 Java 用于一个小型应用程序.它是对现有 MFC 项目的重写.我需要更改现有的 dll 才能使用 JNI 从 Java 进行访问.所有这些 Java 东西对我来说都是新的，所以当我阅读其他论坛帖子时，我遇到了一些麻烦并且感觉相当密集.在现有的 dll 中，我有一个这样的函数:

I'm using Java for a small app. It's a rewrite of an existing MFC project. There is an existing dll that I need to change to enable access from Java using JNI. All of this Java stuff is new to me, so I'm having a little trouble and feeling rather dense when I read other forum posts. In the existing dll I have a function like this:

extern "C" __declspec(dllexport) bool Create()
{
     return TRUE;
}

愚蠢的提问时间.如何正确设置它以供 Java 调用?

Dumb question time. How do I properly set it up to be called by Java?

我试过了:

JNIEXPORT jboolean JNICALL Create()
{
     return TRUE;
}

我包含了 jni.h，一切都可以正常编译.但是，当我从 Java 调用它时，我得到了 UnsatisfiedLinkError.我使用这个从 Java 调用它:

I'm including jni.h and everything compiles fine. However, when I call it from Java I get UnsatisfiedLinkError. I'm calling it from Java using this:

public static native boolean CreateSession();

System.load("D:\JavaCallTest.dll");
Create();

有人可以把我推向正确的方向吗?我真诚地感谢任何帮助.

Could someone kindly push me in the proper direction? I sincerely appreciate any help.

谢谢，

尼克

推荐答案

你需要在你的本地代码中包含 Java 类名和路径，例如如果你的本地方法在 Java 中声明为:

You need to include the Java class name and path in your native code, for example if your native method was declared in Java as:

public class NativeCode {
    public static native boolean CreateSession();
}

并且类路径是(例如)com.example.NativeCode，您将在本机中声明您的方法，如下所示:

and the class path was (for example) com.example.NativeCode you would declare your method in native as follows:

extern "C"
JNIEXPORT jboolean JNICALL Java_com_example_NativeCode_CreateSession(JniEnv* env, jclass clazz)
{
    return JNI_TRUE;
}

所有 JNI 方法都有一个 JNIEnv 指针和类作为它们的前两个参数.

All JNI methods have a JNIEnv pointer and class as their first two parameters.

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