Creating a shared library for JNI in windows

Question

I went through the JNi tutorial online and it worked just fine on a Linux computer. Now I'm trying to make do the same tutorial on windows. When I get to the step 4. Create a Shared Library, I'm stuck. I don't know how to create this shared library on windows. It gives an example using Visual C++ but I don't have that. Any tips or advice out there what I should do? Any help would be greatly appreciated.

Answer 1

//mac.java
class mac
    public native void getMac();
    private native String getLine(String prompt);
    static {
     System.loadLibrary("myMac");//This is myMac.DLL
     /*if generated by borland
     System.loadLibrary("mymac");//This is mymac.dll
     public static void main(String[] args)
    mac mc=new mac();
    String input = mc.getLine("Enter Some Thing ");
    System.out.println("You Entered " + input);
    System.out.println(mc.getMac());
prompt> javac mac.java
prompt> javah -jni mac
Borland compiler
/*mymac.c*/
#include <jni.h>
#include "mac.h"
#include <stdio.h>
JNIEXPORT void JNICALL
Java_mac_getMac(JNIEnv *env, jobject obj)
    printf("I am in  getmac dir in mymac.dll (Borland) \n");
    return;
JNIEXPORT jstring JNICALL
Java_mac_getLine(JNIEnv *env, jobject obj, jstring enter)
    char buf[128];
    const char *str = (*env)->GetStringUTFChars(env, enter, 0);
    printf("%s", str);
    (*env)->ReleaseStringUTFChars(env, enter, str);
    scanf("%s", buf);
    return (*env)->NewStringUTF(env, buf);
To generate DLL
create bcc32.cfg file in %BORLAND_INSTALL%/BCC5/bin Folder
In the bcc32.cfg file add following code
-I"%BORLAND_INSTALL%\BCC55\include;%JAVA_HOME%\include;%JAVA_HOME%\include\win32"
-L"%BORLAND_INSTALL%\BCC55\lib;%BORLAND_INSTALL%\BCC55\Lib\PSDK;"
i.e the path for borland compiler and java.
now goto prompt and say
prompt>bcc32 -tWM -tWD mymac.c
This will create mymac.lib File
Now say
prompt>implib -c mymac.lib mymac.dll
That's it!!
there you are with dll
Now you can run the mac.class file by using java
VC++
Click File->New->Win32Dynamic-Link Library
Give name and Select
A simple DLL project
You will have
myMac.CPP file
// myMac.cpp : Defines the entry point for the DLL application.
#include "stdafx.h"
#include "mac.h"
#include "jni.h" //can copy or give full path
#include <math.h>
BOOL APIENTRY DllMain( HANDLE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
    return TRUE;
JNIEXPORT void JNICALL
Java_mac_getMac(JNIEnv *env, jobject obj)
    printf("You are in getMac (VC++) DLL\n");
JNIEXPORT jstring JNICALL
Java_mac_getLine(JNIEnv *env, jobject obj, jstring enter)
    char buf[128];
    const char *str = env->GetStringUTFChars(enter, 0);
    printf("\n%s", str);
    env->ReleaseStringUTFChars(enter, str);
    scanf("%s", buf);
    return env->NewStringUTF(buf);
Hope this is useful
regards
kanad Deshpande