JNative dll回调函数使用实例

JNative是供java直接调用c++dll的工具包，这样java程序员仅仅知道c++dll中的函数名和参数类型就可以直接调用dll了，省去了使用JNI的繁琐。

下面是一个使用c++dll回调函数的例子：

dll名字JNativeTest.dll

c++代码：

JNativeTest.h：

#ifndef JNativeTes_H
#define JNativeTes_H

// The following ifdef block is the standard way of creating macros which make exporting 
// from a DLL simpler. All files within this DLL are compiled with the JNATIVETEST_EXPORTS
// symbol defined on the command line. this symbol should not be defined on any project
// that uses this DLL. This way any other project whose source files include this file see 
// JNATIVETEST_API functions as being imported from a DLL, wheras this DLL sees symbols
// defined with this macro as being exported.
#ifdef JNATIVETEST_EXPORTS
#define JNATIVETEST_API extern "C" __declspec(dllexport)
#else
#define JNATIVETEST_API __declspec(dllimport)
#endif

typedef void (*pfCallbackTest)(char * msg, char* data, int type); /*回调函数声明*/
// This class is exported from the JNativeTest.dll

JNATIVETEST_API char* fnJNativeTest(char* msg);

JNATIVETEST_API void RegCallback(pfCallbackTest ev);

#endif

/////////////////////////////////////////////////////////////////////////

JNativeTest.cpp：

// JNativeTest.cpp : Defines the entry point for the DLL application.
//

#include <windows.h>
#include "JNativeTest.h"

BOOL APIENTRY DllMain( HANDLE hModule, 
                       DWORD ul_reason_for_call, 
                       LPVOID lpReserved
      )
{
    switch (ul_reason_for_call)
{
   case DLL_PROCESS_ATTACH:
   case DLL_THREAD_ATTACH:
   case DLL_THREAD_DETACH:
   case DLL_PROCESS_DETACH:
    break;
    }
    return TRUE;
}

pfCallbackTest fCallbackTest = NULL;

/*注册回调*/

void RegCallback(pfCallbackTest ev)
{
fCallbackTest = ev;
}

// This is an example of an exported function.
char* fnJNativeTest(char* msg)
{

if (fCallbackTest != NULL)

   fCallbackTest(msg, "Test", 6); /*调用回调函数*/

return msg;
}

///////////////////////////////////////////////////////////////////////////////

java代码：

TestCallback.java

import org.xvolks.jnative.JNative;
import org.xvolks.jnative.exceptions.NativeException;
import org.xvolks.jnative.pointers.*;
import org.xvolks.jnative.util.Callback;

/**
* @date 2009-3-17
* @author charis
* @Copyright (c) qqtech All rights reserved. http://www.qqtech.com
*/
public class TestCallback implements Callback/*实现此接口*/ {

public TestCallback() {
  
}

/**
* Method callback
* java对应于dll中的回调函数
* @param values
*            an long[] 参数数组，非整型数代表的都是地址
* @return an int
* @version 3/17/2008
*/
public int callback(long[] values) {
   if (values == null) {
    System.err.println("callback ret " + 3);
    return 3;
   }
   if (values.length == 3) {
    String name = "";
    try {
     Pointer _pointer = Pointer.createPointerToNativeMemory((int) values[0], 100); /*获取字符串通过指针*/
     Pointer _pointer1 = Pointer.createPointerToNativeMemory((int) values[1], 100);
    
     name = _pointer.getAsString() + "/" + _pointer1.getAsString();
    
    } catch (Exception e1) {
     // TODO Auto-generated catch block
     e1.printStackTrace();
    } 
    System.err.println("lParam " + name + "/" + values[2]);
   
   
    return 1;
   } else {
    System.err.println("Bad number of arguments ! 3 expected "+values.length+" found");
    System.err.println("callback ret " + 2);
    return 2;
   }
}

/**
* java回调函数地址
*/
public int getCallbackAddress() throws NativeException {
   return JNative.createCallback(3/*回调函数参数数目*/, this);
}

}

///////////////////////////////////////////////////////////////////////////////

/**
* TestMain.java
*/

import org.xvolks.jnative.JNative;
import org.xvolks.jnative.Type;

/**
* @date 2009-3-10
* @author charis
* @Copyright (c) qqtech All rights reserved. http://www.qqtech.com
*/
public class TestMain{

public TestMain(){
  
}

/**
* @param args
*/
public static void main(String[] args) {
   // TODO Auto-generated method stub
  
   try {
   
    JNative termcallback = new JNative("JNativeTest.dll", "RegCallback" /*函数名*/ );
    TestCallback _callback = new TestCallback();
    termcallback.setRetVal(Type.VOID);
    termcallback.setParameter(0, _callback.getCallbackAddress()); /*回调函数地址作为参数传递到dll*/
   /**
    * 调用getCallbackAddress后要调用该行代码
    */
    JNative.releaseCallback(_callback);
    termcallback.invoke(); /*注册回调函数*/
   
   
    JNative term = new JNative("JNativeTest.dll", "fnJNativeTest"/*函数名*/);
    term.setRetVal(Type.STRING); /*返回值类型*/
    term.setParameter(0, "hello word!"); /*左起第一个参数，索引为0*/
    term.invoke();
    String value = term.getRetVal();
    System.out.println(value);
   
    term.setParameter(0, "hello word second!");
    term.invoke();
    value = term.getRetVal();
   
    System.out.println(value);
   
   
   } catch (Exception e) {
    e.printStackTrace();
   }
  
}

}

注意：

当调用dll回调函数失败时，请检查参数数目和参数类型，并请c++程序员核对dll中回调函数的声明。

如此typedef void (WINAPI *pfCallbackTest)(char * msg, char* data, int type)声明将会引起调用失败

转载于:https://my.oschina.net/u/2332347/blog/637847