Java 语言添加一个native函数的过程:

Java 语言添加一个native函数的过程:
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主要步骤如下:
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1. 编写java文件. 在本例中是名字是umpFileMain.java
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代码如下:
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/**大连IT门户9b;_F!n'X
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* version 0.00
P6\d%e4]w0 * Copyright (C) 2008 Chen Zuopeng
%hCft4D GZhH9l0 * czp.opensource@gmail.com
C$kP$s3|/pBz0 * http://www.mydlit.com大连IT门户@lo jSgm(F
* This program is free software; you can redistribute it and/or modify
)O)hd wd,uI0 * it under the terms of the GNU General Public License as published by大连IT门户 ?9y+F9{%p5F
* the Free Software Foundation; either version 2 of the License, or
EBlXN5{y+E["z0 * (at your option) any later version.大连IT门户8O BM+M ov~
*/
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public class DumpFileMain
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public static void main (String [] args)大连IT门户9E&R:?1EI&j
{大连IT门户^@1Xq nR3l.I
//DumpFile.DumpFileToScreen (args[1]);
3eI!]S"A0 DumpFile.DumpFileToScreen (”./DumpFile.cpp”);
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`bB5vJ [P/I6m0 static
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System.loadLibrary(”dumpfile”); //这是要生成的动态链接库的名字::libdumpfile.so
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}
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3Yux-D$q7?q5j!m0 class DumpFile大连IT门户lc,R
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"]&_S*M~'U,[0 public static int DumpFileToScreen (String fileName)大连IT门户j X5d v6^D3`@"k
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return nativeDumpFileToScreen (fileName);
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nq$J0 public static native int nativeDumpFileToScreen (String fileName); //这是要调用的C函数的Java的原型
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7c0Sx;V)VU*S0 2. 编译.java文件大连IT门户U}S U h-mf^

-A*g1P/B@c0 在终端下运行javac DumpFileMain.java大连IT门户#Dwr sk
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将会生成DumpFileMain.class文件大连IT门户O ]Q0m(b| }(`2j R*A

{m6Z(XrPw)yr;C1W0 3. 生成C或C++的头文件
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3n.B$G8^0w%[0 在终端下输入javah DumpFile
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8gB&OJf*],Y _{0 将会成生DumpFile.h头文件内容如下:大连IT门户X%^{%Y Qu
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/* DO NOT EDIT THIS FILE - it is machine generated */大连IT门户
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#include <jni.h>
2BCV[N7cv7z0 /* Header for class DumpFile */
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#ifndef _Included_DumpFile
^HX%Cw5Jq%o!U*hD0 #define _Included_DumpFile大连IT门户.V~hIEX5W \:{
#ifdef __cplusplus
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#endif
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SM0 /*大连IT门户/UE\!E~Wc
* Class: DumpFile大连IT门户9T;o,z}F9^
* Method: nativeDumpFileToScreen
fA/RUG-Fh0 * Signature: (Ljava/lang/String;)I大连IT门户4J\Vj1ckT7NIi
*/
D }Z.LYp/K5` N;s0 JNIEXPORT jint JNICALL Java_DumpFile_nativeDumpFileToScreen大连IT门户^9I3K*e\,]$L{*[i)S
(JNIEnv *, jclass, jstring);大连IT门户gy,q"n)l&r5Eg
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#ifdef __cplusplus大连IT门户 hs5G;W[5QQ0|
}
%^8O&X5msl0 #endif大连IT门户z5~}|A
#endif
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4. 对JNICALL Java_DumpFile_nativeDumpFileToScreen函数的实现
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编写一个DumpFile.cpp文件或DumpFile.c文件,内容如下:
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@ |5u6@ZeJ*g0 /**大连IT门户/U J4rM$m0HK5i8\
*
vwZ"n l0 * version 0.00大连IT门户&NHs.dR~'@0k
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* Copyright (C) 2008 Chen Zuopeng
3F(DBK9Ff)oT_#{0 * czp.opensource@gmail.com
/E.W6v)n!wD?W0 * http://www.mydlit.com
ylp7QC)Mq0 * This program is free software; you can redistribute it and/or modify
Q W0H$G)v9Gq0 * it under the terms of the GNU General Public License as published by
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* (at your option) any later version.大连IT门户+|'BT/VIeL[
*/大连IT门户 ~@^'T)W
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#include <iostream>
:x!t+]Vx~\m@!h0 #include <assert.h>
s,vIB7H MF A0 #include <fstream>大连IT门户P8]Sm7x@5C
#include “DumpFile.h”大连IT门户.X5{.iS-W)x
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static int DumpFileToScreen (const char* pFile);
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if (argc != 2)
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hx#}o_0 std::cerr << “Invalid parameters” << std::endl;
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}
2n`HD%iM$_.a(C0 DumpFileToScreen (argv[1]);
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#endif //DEBUG
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"LC$yk]0 static int DumpFileToScreen (const char* pFile)大连IT门户,NuD4Fz'g4R?m7z4Lh
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assert (pFile);大连IT门户Ge2Zk(X.n1X
if (pFile == 0)
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}
mpS,pXET/E0 std::ifstream in (pFile);大连IT门户:A%o.d/I(h@0dv-su
assert (in);大连IT门户:E%kso$E5o
if (in == 0)
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std::cerr << “Failed to open file::” << pFile << std::endl;大连IT门户$wp-v&B/?K)~
return -1;
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-HD2P'F2u[0 std::cout << in.rdbuf () << std::endl;
*YSk6M?0 return 0;
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[}[ ~ ?.s0 JNIEXPORT jint JNICALL Java_DumpFile_nativeDumpFileToScreen(JNIEnv *env, jclass clazz, jstring fileFullName)大连IT门户k qpi1L
{
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U-gCd9?0 const char* c_str_name = (const char*) env->GetStringUTFChars (fileFullName, NULL);大连IT门户
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if (c_str_name == NULL)
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rVal = DumpFileToScreen (c_str_name);
.|j3Yz-zy0 if (c_str_name != NULL)
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env->ReleaseStringUTFChars(fileFullName, c_str_name);
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return rVal;大连IT门户*`S|2~,ZVa_
}
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ED+Z"i2?0 5. 下一步就是生成动太链接库了, Java只能动态链接native函数
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](?i0 gcc(g++) -shared -o libDumpFile.so DumpFile.c (DumpFile.cpp) -I.大连IT门户C:g/C^pyfi

y2\'U9M2j(PV0 6. 好了, 所有的工作都做完了, 可以跑了, 为了让代码可以找到libDumpFile.so文件要先export LD_LIBRARY_PATH=./一下.
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输入java DumpFileMain.class
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done!! ^_^大连IT门户r/h6y#{"z9h
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java_native_ex.zip
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Q9N3B0s.QL!l0(2008-05-30 13:30:35, Size: 2.51 KB, Downloads: 0)大连IT门户t G?1t[