JNIdemo

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package
com.jni;

public class JNITest {

    static{

        System.loadLibrary("JNI");

    }

    public
native String getCompterName();

    public
native void fastWriteFile(String name, byte[] bytes);

    public
static void main(String[] args) {

        JNITest test = new
JNITest();

        String str = test.getCompterName();

        test.fastWriteFile("tst", new
byte[]{});

        System.out.println(str);

    }

}

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/* DO NOT EDIT THIS FILE - it is machine generated */

#include <jni.h>

/* Header for class com_jni_JNITest */

#ifndef _Included_com_jni_JNITest

#define _Included_com_jni_JNITest

#ifdef __cplusplus

extern
"C" {

#endif

/*

 * Class:     com_jni_JNITest

 * Method:    getCompterName

 * Signature: ()Ljava/lang/String;

 */

JNIEXPORT jstring JNICALL Java_com_jni_JNITest_getCompterName

  (JNIEnv *, jobject);

/*

 * Class:     com_jni_JNITest

 * Method:    fastWriteFile

 * Signature: (Ljava/lang/String;[B)V

 */

JNIEXPORT void
JNICALL Java_com_jni_JNITest_fastWriteFile

  (JNIEnv *, jobject, jstring, jbyteArray);

#ifdef __cplusplus

}

#endif

#endif

//-------------------------------------

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/* Replace "dll.h" with the name of your header */

#include <stdlib.h>

#include <stdio.h>

#include "dll.h"

#include "windows.h"

#include "tlhelp32.h"

#include "util.h"

/*

* Class: com_jni_JNITest

* Method: getCompterName

* Signature: ()Ljava/lang/String;

*/

JNIEXPORT jstring JNICALL Java_com_jni_JNITest_getCompterName

(JNIEnv *env, jobject)

{

char
*res = "test to jstring";

PROCESSENTRY32 pe32;

//在使用这个结构前，先设置它的大小

pe32.dwSize = sizeof(pe32);

//给系统内所有的进程拍个快照

HANDLE
hProcessSnap = ::CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS,0);

if
(hProcessSnap == INVALID_HANDLE_VALUE)

{

res = "CreateToolhelp32Snapshot 调用失败.\n";

}

//遍历进程快照，轮流显示每个进程的信息

BOOL
bMore = ::Process32First(hProcessSnap,&pe32);

while
(bMore)

{

printf("进程名称:%s ID:%u\n",pe32.szExeFile,pe32.th32ProcessID);

bMore = ::Process32Next(hProcessSnap,&pe32);

}

//不要忘记清除掉snapshot对象

::CloseHandle(hProcessSnap);

jstring result = stoJstring(env,res);

return
result;

}

/*

* Class: com_jni_JNITest

* Method: fastWriteFile

* Signature: (Ljava/lang/String;[B)V

*/

JNIEXPORT void
JNICALL Java_com_jni_JNITest_fastWriteFile

(JNIEnv *env, jobject, jstring, jbyteArray)

{

printf("hello jni");

}

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  //-------------------------

#include <stdlib.h> 

#include <stdio.h>

#include "dll.h"

//char* to jstring

jstring stoJstring(JNIEnv* env, const
char* pat)

{

    jclass strClass = env->FindClass("Ljava/lang/String;");

    jmethodID ctorID = env->GetMethodID(strClass, "<init>", "([BLjava/lang/String;)V");

    jbyteArray bytes = env->NewByteArray(strlen(pat));

    env->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte*)pat);

    jstring encoding = env->NewStringUTF("utf-8");

    return
(jstring)env->NewObject(strClass, ctorID, bytes, encoding);

}

char* jstringTostring(JNIEnv* env, jstring jstr)

{

       char* rtn = NULL;

       jclass clsstring = env->FindClass("java/lang/String");

       jstring strencode = env->NewStringUTF("utf-8");

       jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");

       jbyteArray barr= (jbyteArray)env->CallObjectMethod(jstr, mid, strencode);

       jsize alen = env->GetArrayLength(barr);

       jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);

       if
(alen > 0)

       {

                 rtn = (char*)malloc(alen + 1);

                 memcpy(rtn, ba, alen);

                 rtn[alen] = 0;

       }

       env->ReleaseByteArrayElements(barr, ba, 0);

       return
rtn;

}