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JNI 测试： Java与C互相调用

分类： Java

2013-05-10 11:30:57

1. 背景： 实现了一个Linux C核心模块，同时实现了Console 与 GTK 的显示，现在需要实现一个Java的界面程序。
2. 功能： GUI 向后台注册一个回调函数，核心模块得到一些结果后，调用注册的回调函数向 GUI 返回数据。

测试 JNI 代码如下，具体JNI编程可以参考资料(像 JNI 编程指南)：

C语言代码：

点击(此处)折叠或打开

  1. [File: call_back.h]

  3. #ifndef _CALL_BACK_H_
  4. #define _CALL_BACK_H_

  6. #include <time.h>

  8. #ifdef __cplusplus
  9. extern \"C\" {
  10. #endif

  12. struct _CallBackBody;
  13. typedef struct _CallBackBody CallBackBody;

  15. typedef void (*CallBackInfoPrintFunc)(
  16.             unsigned long total_line,
  17.             int code_line,
  18.             time_t modify_time,
  19.             const char * file_name
  20.             );

  22. CallBackBody* callback_create(CallBackInfoPrintFunc info_print);

  24. int callback_run(CallBackBody* thiz);

  26. void callback_destroy(CallBackBody* thiz);

  28. #ifdef __cplusplus
  29. }
  30. #endif

  32. #endif/*_CALL_BACK_H_*/

点击(此处)折叠或打开

  1. [File: call_back.c]

  3. #include \"call_back.h\"
  4. #include <stdlib.h>

  6. struct _CallBackBody
  7. {
  8.     int call_num;
  9.     CallBackInfoPrintFunc print;
  10. };

  12. CallBackBody* callback_create(CallBackInfoPrintFunc info_print)
  13. {
  14.     CallBackBody* thiz = (CallBackBody *)malloc(sizeof(CallBackBody));

  16.     if (thiz != NULL)
  17.     {
  18.         thiz->print = info_print;
  19.         thiz->call_num = 0;
  20.     }

  22.     return thiz;
  23. }

  25. int callback_run(CallBackBody* thiz)
  26. {
  27.     if (thiz != NULL && thiz->print != NULL)
  28.     {
  29.         ++thiz->call_num;
  30.         unsigned long total_line = thiz->call_num * 100 + 10;
  31.         int code_line = thiz->call_num * 100 - 20;
  32.         code_line = code_line < 0 ? 0 : code_line;
  33.         time_t now;
  34.         time(&now);
  35.         char* file_name = \"/home/vincent/call_back.c\";

  37.         thiz->print(total_line, code_line, now, file_name);
  38.         
  39.         return 1;
  40.     }

  42.     return -1;
  43. }

  45. void callback_destroy(CallBackBody* thiz)
  46. {
  47.     free(thiz);

  49.     return;
  50. }

Java代码：

点击(此处)折叠或打开

[File: JniInterface.java]

public class JniInterface
{
    private static native void   callbackInitIds();
    public static native boolean callbackCreate();
    public static native boolean callbackRun(String file);
    public static native void    callbackDestroy();

    public static void DataShowCallBackFunc(
            long totalLine,
            int  codeLine,
            String modifyTime,
            String fileName
            )
    {
        System.out.println("[Info]: totalLine = " + totalLine
                            + " codeLine = " + codeLine
                            + " modifyTime = " + modifyTime
                            + " fileName = " + fileName);
    }

    public static void main(String[] args)
    {
        if (JniInterface.callbackCreate())
  {
            try
            {
                while (true)
                {
                    if (JniInterface.callbackRun("/pet/vincent_deng/test"))
              {
              }
                    else
                    {
               System.out.println("[Info]: Run false...");
                    }

                    Thread.sleep(5000);
                }
            }
            catch (Exception ex)
            {
            }
            finally
            {
                JniInterface.callbackDestroy();
            }
  }
  else
  {
   System.out.println("[Info]: Create false...");
  }
    }

    static
    {  
  
        System.loadLibrary("callback");
        callbackInitIds();
    }
}


编译 JniInterface.java 得到 JniInterface.class, 再使用 javah 命令【javah JniInterface】得到 JniInterface.h 文件，拷贝 JniInterface.h 为 JniInterface.c 并修改：

点击(此处)折叠或打开

  1. [File: JniInterface.h]

  3. /* DO NOT EDIT THIS FILE - it is machine generated */
  4. #include <jni.h>
  5. /* Header for class JniInterface */

  7. #ifndef _Included_JniInterface
  8. #define _Included_JniInterface
  9. #ifdef __cplusplus
  10. extern \"C\" {
  11. #endif
  12. /*
  13.  * Class: JniInterface
  14.  * Method: callbackInitIds
  15.  * Signature: ()V
  16.  */
  17. JNIEXPORT void JNICALL Java_JniInterface_callbackInitIds
  18.   (JNIEnv *, jclass);

  20. /*
  21.  * Class: JniInterface
  22.  * Method: callbackCreate
  23.  * Signature: ()Z
  24.  */
  25. JNIEXPORT jboolean JNICALL Java_JniInterface_callbackCreate
  26.   (JNIEnv *, jclass);

  28. /*
  29.  * Class: JniInterface
  30.  * Method: callbackRun
  31.  * Signature: (Ljava/lang/String;)Z
  32.  */
  33. JNIEXPORT jboolean JNICALL Java_JniInterface_callbackRun
  34.   (JNIEnv *, jclass, jstring);

  36. /*
  37.  * Class: JniInterface
  38.  * Method: callbackDestroy
  39.  * Signature: ()V
  40.  */
  41. JNIEXPORT void JNICALL Java_JniInterface_callbackDestroy
  42.   (JNIEnv *, jclass);

  44. #ifdef __cplusplus
  45. }
  46. #endif
  47. #endif

 

点击(此处)折叠或打开

  1. [File: JniInterface.c]

  3. /* Source for class JniInterface */
  4. #include \"JniInterface.h\"
  5. #include \"call_back.h\"
  6. #include \"time.h\"

  8. #define CALLBACK_FUNC_NAME \"DataShowCallBackFunc\"

  10. static CallBackBody* s_callBackBody = NULL;
  11. static jclass s_class = NULL;
  12. static jmethodID s_methodId = NULL;
  13. static JNIEnv* s_env = NULL;

  15. void callBackFunc(
  16.             unsigned long total_line,
  17.             int code_line,
  18.             time_t modify_time,
  19.             const char * file_name
  20.             )
  21. {
  22.     char buf[512];
  23.     struct tm tm_buf;

  25.     if (strftime(buf, sizeof(buf), \"[%G-%m-%d %H:%M:%S]\", localtime_r(&modify_time, &tm_buf)) == 0)
  26.     {
  27.         buf[0] = \'\\0\';
  28.     }

  30.     jlong totalLine = total_line;
  31.     jint codeLine = code_line;
  32.     jstring modifyTime = (*s_env)->NewStringUTF(s_env, buf);
  33.     jstring fileName = (*s_env)->NewStringUTF(s_env, file_name);
  34.     (*s_env)->CallStaticVoidMethod(
  35.                           s_env,
  36.                           s_class,
  37.                           s_methodId,
  38.                           totalLine,
  39.                           codeLine,
  40.                           modifyTime,
  41.                           fileName);
  42. }

  44. /*
  45.  * Class: JniInterface
  46.  * Method: callbackInitIds
  47.  * Signature: ()V
  48.  */
  49. JNIEXPORT void JNICALL Java_JniInterface_callbackInitIds
  50.   (JNIEnv *env, jclass cls)
  51. {
  52.     s_methodId = (*env)->GetStaticMethodID(env, cls, CALLBACK_FUNC_NAME, \"(JILjava/lang/String;Ljava/lang/String;)V\");
  53.     //s_env = (*env)->NewGlobalRef(env, env);
  54.     s_env = env;
  55.     s_class = (*env)->NewGlobalRef(env, cls);
  56. }

  58. /*
  59.  * Class: JniInterface
  60.  * Method: callbackCreate
  61.  * Signature: ()Z
  62.  */
  63. JNIEXPORT jboolean JNICALL Java_JniInterface_callbackCreate
  64.   (JNIEnv *env, jclass cls)
  65. {
  66.     if (s_methodId == NULL
  67.         || s_env == NULL
  68.         || s_class == NULL)
  69.     {
  70.         return JNI_FALSE;
  71.     }

  73.     if (s_callBackBody == NULL)
  74.     {
  75.         s_callBackBody = callback_create(callBackFunc);
  76.     }

  78.     return s_callBackBody == NULL ? JNI_FALSE : JNI_TRUE;
  79. }

  81. /*
  82.  * Class: JniInterface
  83.  * Method: callbackRun
  84.  * Signature: (Ljava/lang/String;)Z
  85.  */
  86. JNIEXPORT jboolean JNICALL Java_JniInterface_callbackRun
  87.   (JNIEnv *env, jclass cls, jstring file)
  88. {
  89.     int rst;
  90.     const jbyte *str = (*env)->GetStringUTFChars(env, file, NULL);
  91.     
  92.     if (str == NULL)
  93.     {
  94.         return JNI_FALSE;
  95.     }
  96.     
  97.     rst = callback_run(s_callBackBody);
  98.     
  99.     (*env)->ReleaseStringUTFChars(env, file, str);

  101.     return rst < 0 ? JNI_FALSE : JNI_TRUE;
  102. }

  104. /*
  105.  * Class: JniInterface
  106.  * Method: callbackDestroy
  107.  * Signature: ()V
  108.  */
  109. JNIEXPORT void JNICALL Java_JniInterface_callbackDestroy
  110.   (JNIEnv *env, jclass cls)
  111. {
  112.     s_env = NULL;
  113.     //(*env)->DeleteGlobalRef(env, s_env);
  114.     (*env)->DeleteGlobalRef(env, s_class);
  115.     callback_destroy(s_callBackBody);
  116.     s_callBackBody = NULL;
  117. }

最后将 call_back.c 和 JniInterface.c 编译为 libcallback.so, 再执行 Java文件即可，简单Makefile, 其中的路径【/usr/java/default/include/】 和 【/usr/java/default/include/linux】需要修改为系统对应的jdk路径：

 

点击(此处)折叠或打开

  1. .PHONY: clean
  3. libcallback.so: call_back.o JniInterface.o
  4. gcc -Wall -fPIC -rdynamic -shared -o $@ $^
  6. %.o: %.c
  7. gcc -Wall -c -o $@ -I./ -I/usr/java/default/include/ -I/usr/java/default/include/linux $(filter %.c, $^)
  9. clean:
  10. -rm *.so *.o
执行结果如下：

 

点击(此处)折叠或打开

  1. [tester@dellquad JavaCallC]$ export LD_LIBRARY_PATH=.
  2. [tester@dellquad JavaCallC]$ make
  3. gcc -Wall -c -o call_back.o -I./ -I/usr/java/default/include/ -I/usr/java/default/include/linux call_back.c
  4. gcc -Wall -c -o JniInterface.o -I./ -I/usr/java/default/include/ -I/usr/java/default/include/linux JniInterface.c
  5. gcc -Wall -fPIC -rdynamic -shared -o libcallback.so call_back.o JniInterface.o
  6. [tester@dellquad JavaCallC]$ javac JniInterface.java
  7. [tester@dellquad JavaCallC]$ java JniInterface
  8. [Info]: totalLine = 110 codeLine = 80 modifyTime = [2013-05-10 12:15:43] fileName = /home/vincent/call_back.c
  9. [Info]: totalLine = 210 codeLine = 180 modifyTime = [2013-05-10 12:15:48] fileName = /home/vincent/call_back.c
  10. [Info]: totalLine = 310 codeLine = 280 modifyTime = [2013-05-10 12:15:53] fileName = /home/vincent/call_back.c
  11. [Info]: totalLine = 410 codeLine = 380 modifyTime = [2013-05-10 12:15:58] fileName = /home/vincent/call_back.c
  12. [Info]: totalLine = 510 codeLine = 480 modifyTime = [2013-05-10 12:16:03] fileName = /home/vincent/call_back.c
  13. [Info]: totalLine = 610 codeLine = 580 modifyTime = [2013-05-10 12:16:08] fileName = /home/vincent/call_back.c
  14. [Info]: totalLine = 710 codeLine = 680 modifyTime = [2013-05-10 12:16:13] fileName = /home/vincent/call_back.c
  15. [Info]: totalLine = 810 codeLine = 780 modifyTime = [2013-05-10 12:16:18] fileName = /home/vincent/call_back.c
  16. [Info]: totalLine = 910 codeLine = 880 modifyTime = [2013-05-10 12:16:23] fileName = /home/vincent/call_back.c
  17. [Info]: totalLine = 1010 codeLine = 980 modifyTime = [2013-05-10 12:16:28] fileName = /home/vincent/call_back.c
  18. [Info]: totalLine = 1110 codeLine = 1080 modifyTime = [2013-05-10 12:16:33] fileName = /home/vincent/call_back.c
  19. [Info]: totalLine = 1210 codeLine = 1180 modifyTime = [2013-05-10 12:16:38] fileName = /home/vincent/call_back.c
  20. [Info]: totalLine = 1310 codeLine = 1280 modifyTime = [2013-05-10 12:16:43] fileName = /home/vincent/call_back.c
  21. [Info]: totalLine = 1410 codeLine = 1380 modifyTime = [2013-05-10 12:16:48] fileName = /home/vincent/call_back.c
  22. [Info]: totalLine = 1510 codeLine = 1480 modifyTime = [2013-05-10 12:16:53] fileName = /home/vincent/call_back.c
  23. [Info]: totalLine = 1610 codeLine = 1580 modifyTime = [2013-05-10 12:16:58] fileName = /home/vincent/call_back.c
  24. [Info]: totalLine = 1710 codeLine = 1680 modifyTime = [2013-05-10 12:17:03] fileName = /home/vincent/call_back.c
  25. [Info]: totalLine = 1810 codeLine = 1780 modifyTime = [2013-05-10 12:17:08] fileName = /home/vincent/call_back.c
  26. [Info]: totalLine = 1910 codeLine = 1880 modifyTime = [2013-05-10 12:17:13] fileName = /home/vincent/call_back.c

  28. [tester@dellquad JavaCallC]$

代码：上传JavaCallC.tar.bz2 说不支持该类型文件，改成了 JavaCallC.tar.bz2.txt 上传，下载后改回来即可。
JavaCallC.tar.bz2.txt



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