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(){ } 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
原文链接:http://hi.baidu.com/chinacharis/blog/item/87ef7f00b0b092067bec2cfb.html