上一篇《JAVA本地接口（JNI）》中介紹了JAVA的JNI技術(shù)，通過JAVA自有的方式調(diào)用動(dòng)態(tài)鏈接庫(kù)，這一篇將繼續(xù)為大家介紹使用其他方式調(diào)用動(dòng)態(tài)鏈接庫(kù)。
首先，我們編寫一個(gè)用于測(cè)試的鏈接庫(kù)

頭文件 print.h

#ifdef DLL_IMPLEMENT #define DLL_API __declspec(dllexport) #else #define DLL_API __declspec(dllimport) #endif #ifndef _Included_PRINT#define _Included_PRINT#ifdef __cplusplusextern "C" {#endifDLL_API void print();DLL_API void print2(int i);DLL_API int print3(int i);#ifdef __cplusplus}#endif #endif

源文件 print.c

#define DLL_IMPLEMENT #include <stdio.h> #include "print.h" DLL_API void print() {printf("invoke print..."); } DLL_API void print2(int i) {printf("invoke print %d...", i); } DLL_API int print3(int i) {return i; }

使用c編譯器對(duì)其進(jìn)行編譯：cl -LD print.c -Feprint.dll
然后我們將生成的print.dll放在系統(tǒng)的system32文件夾下，至此準(zhǔn)備工作完成。

JNative

JNative是Java to native interface的縮寫，使用JNative，我們可以很方便的調(diào)用動(dòng)態(tài)鏈接庫(kù)，使用示例如下：

import org.xvolks.jnative.JNative; import org.xvolks.jnative.Type;public class JNativeTest {public static void main(String[] args) throws Exception{// 加載動(dòng)態(tài)鏈接庫(kù)JNative print = new JNative("print.dll", "print");// 執(zhí)行函數(shù)print.invoke();JNative print2 = new JNative("print.dll", "print2");// 設(shè)置函數(shù)形參print2.setParameter(0, 2);print2.invoke();JNative print3 = new JNative("print.dll", "print3");// 設(shè)置返回值類型print3.setRetVal(Type.INT);print3.setParameter(0, 3);print3.invoke();// 獲得運(yùn)行結(jié)果String result = print3.getRetVal();System.out.println("print3:" + result);} }

下面再給出一個(gè)使用JNative獲得系統(tǒng)時(shí)間的示例：

import org.xvolks.jnative.JNative; import org.xvolks.jnative.exceptions.NativeException; import org.xvolks.jnative.misc.basicStructures.AbstractBasicData; import org.xvolks.jnative.pointers.Pointer; import org.xvolks.jnative.pointers.memory.MemoryBlockFactory; import org.xvolks.jnative.util.Kernel32.SystemTime;public class JNativeDemo extends AbstractBasicData<JNativeDemo> {public short wYear;public short wMonth;public short wDayOfWeek;public short wDay;public short wHour;public short wMinute;public short wSecond;public short wMilliseconds;/*** 分配內(nèi)存，并返回指針*/public Pointer createPointer() throws NativeException{pointer = new Pointer(MemoryBlockFactory.createMemoryBlock(getSizeOf()));return pointer;}/*** 內(nèi)存大小*/public int getSizeOf(){return 8 * 2;}/*** 獲取通過內(nèi)存指針解析出結(jié)果*/public JNativeDemo getValueFromPointer() throws NativeException{wYear = getNextShort();wMonth = getNextShort();wDayOfWeek = getNextShort();wDay = getNextShort();wHour = getNextShort();wMinute = getNextShort();wSecond = getNextShort();wMilliseconds = getNextShort();return this;}public JNativeDemo() throws NativeException{super(null);createPointer();}public String toString(){return wYear + "/" + wMonth + "/" + wDay + " at + " + wHour + ":"+ wMinute + ":" + wSecond + ":" + wMilliseconds;}public static SystemTime GetSystemTime() throws NativeException,IllegalAccessException{// 創(chuàng)建對(duì)象JNative nGetSystemTime = new JNative("Kernel32.dll", "GetSystemTime");SystemTime systemTime = new SystemTime();// 設(shè)置參數(shù)nGetSystemTime.setParameter(0, systemTime.getPointer());nGetSystemTime.invoke();// 解析結(jié)構(gòu)指針內(nèi)容return systemTime.getValueFromPointer();}public static void main(String[] args) throws NativeException,IllegalAccessException{System.err.println(GetSystemTime());} }

JNA

JNA（Java Native Access ）提供一組Java工具類用于在運(yùn)行期動(dòng)態(tài)訪問系統(tǒng)本地庫(kù)（native library：如Window的dll）而不需要編寫任何Native/JNI代碼。開發(fā)人員只要在一個(gè)java接口中描述目標(biāo)native library的函數(shù)與結(jié)構(gòu)，JNA將自動(dòng)實(shí)現(xiàn)Java接口到native function的映射。

使用示例：

import com.sun.jna.Library; import com.sun.jna.Native;public class JNADemo {// 定義接口CLibrary，繼承自com.sun.jna.Librarypublic interface CLibrary extends Library{// 定義并初始化接口的靜態(tài)變量CLibrary Instance = (CLibrary) Native.loadLibrary("print", CLibrary.class);// 函數(shù)聲明void print();void print2(int i);int print3(int i);}public static void main(String[] args){CLibrary.Instance.print();CLibrary.Instance.print2(2);System.out.println("print3:" + CLibrary.Instance.print3(3));} }

JNative和JNA都可以實(shí)現(xiàn)對(duì)DLL的調(diào)用，但二者各有優(yōu)缺點(diǎn)，需要根據(jù)實(shí)際情況選擇。

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