import java.io.*;
 
public class Hello {
    static {
        System.loadLibrary("Hello");
    }
 
    public native int MessageBox( int hwnd, String text, String title, int type );
 
    public static void main(String args[]) {
        Hello hello = new Hello();
        hello.MessageBox( 0, "Hello, Win32 API(JNI) World!", "Hello, World!", 0 );
    }
}

import java.io.*; public class Hello { static { System.loadLibrary("Hello"); } public native int MessageBox( int hwnd, String text, String title, int type ); public static void main(String args[]) { Hello hello = new Hello(); hello.MessageBox( 0, "Hello, Win32 API(JNI) World!", "Hello, World!", 0 ); } }

C:¥> javah -jni Hello

C:¥> javah -jni Hello

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class Hello */
 
#ifndef _Included_Hello
#define _Included_Hello
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     Hello
 * Method:    MessageBox
 * Signature: (ILjava/lang/String;Ljava/lang/String;I)I
 */
JNIEXPORT jint JNICALL Java_Hello_MessageBox
  (JNIEnv *, jobject, jint, jstring, jstring, jint);
 
#ifdef __cplusplus
}
#endif
#endif

/* DO NOT EDIT THIS FILE - it is machine generated */ #include <jni.h> /* Header for class Hello */ #ifndef _Included_Hello #define _Included_Hello #ifdef __cplusplus extern "C" { #endif /* * Class: Hello * Method: MessageBox * Signature: (ILjava/lang/String;Ljava/lang/String;I)I */ JNIEXPORT jint JNICALL Java_Hello_MessageBox (JNIEnv *, jobject, jint, jstring, jstring, jint); #ifdef __cplusplus } #endif #endif

#include "Hello.h"
#include <windows.h>
 
/*
 * Class:     Hello
 * Method:    MessageBox
 * Signature: (ILjava/lang/String;Ljava/lang/String;I)I
 */
JNIEXPORT jint JNICALL Java_Hello_MessageBox
  (JNIEnv* env, jobject me, jint hwnd, jstring text, jstring caption, jint type)
{
#ifdef UNICODE
    const jchar* _text = env->GetStringChars(text, 0); 
    const jchar* _caption = env->GetStringChars(caption, 0); 
    const int result = MessageBoxW(NULL, (LPCWSTR)_text, (LPCWSTR)_caption, type); 
    env->ReleaseStringChars(text, _text); 
    env->ReleaseStringChars(caption, _caption); 
#else
    /* このコードはマルチバイト文字（MBCS）を考慮していない為、全角文字列を渡した場合に文字化けする。正しくは SJIS に変換する処理が必要。*/
    const char* _text = env->GetStringUTFChars(text, 0); 
    const char* _caption = env->GetStringUTFChars(caption, 0); 
    const int result = MessageBoxA(NULL, (LPCSTR)_text, (LPCSTR)_caption, type); 
    env->ReleaseStringUTFChars(text, _text); 
    env->ReleaseStringUTFChars(caption, _caption); 
#endif
    return result; 
}

#include "Hello.h" #include <windows.h> /* * Class: Hello * Method: MessageBox * Signature: (ILjava/lang/String;Ljava/lang/String;I)I */ JNIEXPORT jint JNICALL Java_Hello_MessageBox (JNIEnv* env, jobject me, jint hwnd, jstring text, jstring caption, jint type) { #ifdef UNICODE const jchar* _text = env->GetStringChars(text, 0); const jchar* _caption = env->GetStringChars(caption, 0); const int result = MessageBoxW(NULL, (LPCWSTR)_text, (LPCWSTR)_caption, type); env->ReleaseStringChars(text, _text); env->ReleaseStringChars(caption, _caption); #else /* このコードはマルチバイト文字（MBCS）を考慮していない為、全角文字列を渡した場合に文字化けする。正しくは SJIS に変換する処理が必要。*/ const char* _text = env->GetStringUTFChars(text, 0); const char* _caption = env->GetStringUTFChars(caption, 0); const int result = MessageBoxA(NULL, (LPCSTR)_text, (LPCSTR)_caption, type); env->ReleaseStringUTFChars(text, _text); env->ReleaseStringUTFChars(caption, _caption); #endif return result; }

C:¥> SET INCLUDE=%JAVA_HOME%include;%JAVA_HOME%includewin32;%INCLUDE%
C:¥> cl Hello.cpp /LD /link user32.lib

C:¥> SET INCLUDE=%JAVA_HOME%include;%JAVA_HOME%includewin32;%INCLUDE% C:¥> cl Hello.cpp /LD /link user32.lib

C:¥> javac Hello.java
C:¥> java Hello

C:¥> javac Hello.java C:¥> java Hello

---------------------------
Hello, World!
---------------------------
Hello, Win32 API(JNI) World!
---------------------------
OK   
---------------------------

--------------------------- Hello, World! --------------------------- Hello, Win32 API(JNI) World! --------------------------- OK ---------------------------