在Java中调用C语言的DLL的一个方式就是JNI( Java Native Interface)。但是,在VC++ 6.0中编译JNI DLL遇到一个小问题。例如: Java定义如下:
public class NTPortJava
{
// Returns a value indicates whether the application is running under Windows NT/2000 system.
public native static boolean IsWinNT();
} 使用Javah可以生成如下的函数定义:
/*
* Class: NTPortJava_NTPortJava
* Method: IsWinNT
* Signature: ()Z
*/
JNIEXPORT jboolean JNICALL Java_NTPortJava_NTPortJava_IsWinNT
(JNIEnv *, jclass);
如果编写好Java_NTPortJava_NTPortJava_IsWinNT进行编译链接也可以正常生成DLL,但是使用Dependency Walker可以发现DLL中导出的函数不是Java_NTPortJava_NTPortJava_IsWinNT,而是_Java_NTPortJava_NTPortJava_IsWinNT@0。出现这个问题的原因是JNIEXPORT在jnimd.h 的定义:
#define JNIEXPORT __declspec(dllexport)Visual C++对于__declspec(dllexport)的处理就是在导出函数的前后添加修饰符号。解决问题的办法很简单,只需要建立一个.def文件就可以了:
LIBRARY NTPortJava
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EXPORTS
Java_NTPortJava_NTPortJava_IsWinNT这样编译链接后产生的DLL就满足要求了。
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