我最近在写一个j2se的程序，我用的是开源的org.amse.ys.zip包里的代码，这部分代码是在FBReaderJ里抽取的，但是其中包含了一些native的方法，需要用的zlib库，而FBReaderJ由于是运行在Android平台上的，它对应的so库肯定是无法在我的程序中使用，因此，在下载了zlib的win32运行库后，我使用 

1 javah -jni org.amse.ys.zip.DeflatingDecompressor

生成了org_amse_ys_zip_DeflatingDecompressor.h 头文件，内容如下：

1 /* DO NOT EDIT THIS FILE - it is machine generated */ 2 #include "jni.h" 3 /* Header for class org_amse_ys_zip_DeflatingDecompressor */ 4  5 #ifndef _Included_org_amse_ys_zip_DeflatingDecompressor 6 #define _Included_org_amse_ys_zip_DeflatingDecompressor 7 #ifdef __cplusplus 8 extern "C" { 9 #endif10 #undef org_amse_ys_zip_DeflatingDecompressor_IN_BUFFER_SIZE11 #define org_amse_ys_zip_DeflatingDecompressor_IN_BUFFER_SIZE 2048L12 #undef org_amse_ys_zip_DeflatingDecompressor_OUT_BUFFER_SIZE13 #define org_amse_ys_zip_DeflatingDecompressor_OUT_BUFFER_SIZE 32768L14 /*15  * Class:     org_amse_ys_zip_DeflatingDecompressor16  * Method:    startInflating17  * Signature: ()I18  */19 JNIEXPORT jint JNICALL Java_org_amse_ys_zip_DeflatingDecompressor_startInflating20   (JNIEnv *, jobject);21 22 /*23  * Class:     org_amse_ys_zip_DeflatingDecompressor24  * Method:    endInflating25  * Signature: (I)V26  */27 JNIEXPORT void JNICALL Java_org_amse_ys_zip_DeflatingDecompressor_endInflating28   (JNIEnv *, jobject, jint);29 30 /*31  * Class:     org_amse_ys_zip_DeflatingDecompressor32  * Method:    inflate33  * Signature: (I[BII[B)J34  */35 JNIEXPORT jlong JNICALL Java_org_amse_ys_zip_DeflatingDecompressor_inflate36   (JNIEnv *, jobject, jint, jbyteArray, jint, jint, jbyteArray);37 38 #ifdef __cplusplus39 }40 #endif41 #endif

建立VS2005 DLL工程，加入jni.h, jni_md.h, zlib的 zconf.h, 加入zdll.lib依赖，加入DeflatingDecompressor.cpp:

1 /* 2  * Copyright (C) 2009-2013 Geometer Plus 
     
       3  * 4  * This program is free software; you can redistribute it and/or modify 5  * it under the terms of the GNU General Public License as published by 6  * the Free Software Foundation; either version 2 of the License, or 7  * (at your option) any later version. 8  * 9  * This program is distributed in the hope that it will be useful,10  * but WITHOUT ANY WARRANTY; without even the implied warranty of11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the12  * GNU General Public License for more details.13  *14  * You should have received a copy of the GNU General Public License15  * along with this program; if not, write to the Free Software16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA17  * 02110-1301, USA.18  */19 #include 
      
       20 #include "zlib.h"21 22 #include 
       
        23 #include "jni.h"24 #include "org_amse_ys_zip_DeflatingDecompressor.h"25 26 #define                                SIZE                            1027 28 static z_stream*            ourStreams[SIZE]            = { 0 };29 30 extern "C"31 JNIEXPORT jint JNICALL Java_org_amse_ys_zip_DeflatingDecompressor_startInflating(JNIEnv *env, jobject thiz) {32     int i;33     for (i = 0; i < SIZE; ++i) {34         if (ourStreams[i] == 0) {35             ourStreams[i] = new z_stream;36             memset(ourStreams[i], 0, sizeof(z_stream));37             inflateInit2(ourStreams[i], -MAX_WBITS);38             return i;39         }40     }41     return -1;42 }43 44 extern "C"45 JNIEXPORT void JNICALL Java_org_amse_ys_zip_DeflatingDecompressor_endInflating(JNIEnv *env, jobject thiz, jint inflatorId) {46     if (inflatorId >= 0 && inflatorId < SIZE) {47         inflateEnd(ourStreams[inflatorId]);48         delete ourStreams[inflatorId];49         ourStreams[inflatorId] = 0;50     }51 }52 53 // returns (endFlag << 32) + ((used inLength) << 16) + outLength54 extern "C"55 JNIEXPORT jlong JNICALL Java_org_amse_ys_zip_DeflatingDecompressor_inflate(JNIEnv *env, jobject thiz, jint inflatorId, jbyteArray in, jint inOffset, jint inLength, jbyteArray out) {56     if (inflatorId < 0 || inflatorId >= SIZE) {57         return -1;58     }59     z_stream *stream = ourStreams[inflatorId];60     if (stream == 0) {61         return -2;62     }63 64     jbyte* inStart = env->GetByteArrayElements(in, 0);65     jbyte* outStart = env->GetByteArrayElements(out, 0);66     stream->next_in = (Bytef*)inStart + inOffset;67     stream->avail_in = inLength;68     stream->next_out = (Bytef*)outStart;69     const int outLength = env->GetArrayLength(out);70     stream->avail_out = outLength;71     const int code = inflate(stream, Z_SYNC_FLUSH);72     env->ReleaseByteArrayElements(in, inStart, 0);73     env->ReleaseByteArrayElements(out, outStart, 0);74     if (code == Z_OK || code == Z_STREAM_END) {75         jlong result = ((inLength - stream->avail_in) << 16) + outLength - stream->avail_out;76         if (code == Z_STREAM_END) {77             result |= ((jlong)1) << 32;78         }79         return result;80     }81     return -1024 + code;82 }
       
      
     

成功编译出DeflatingDecompressor.dll文件。

然后在的j2se工程的DeflatingDecompressor.java中使用

1 static {2     System.loadLibrary("libs/DeflatingDecompressor");3 }

加载动态库，得到

1 Exception in thread "main" java.lang.UnsatisfiedLinkError: D:\Works\TextLayout\NewReaderSE\libs\DeflatingDecompressor.dll: Can't find dependent libraries2     at java.lang.ClassLoader$NativeLibrary.load(Native Method)3     at java.lang.ClassLoader.loadLibrary0(Unknown Source)4     at java.lang.ClassLoader.loadLibrary(Unknown Source)5     at java.lang.Runtime.loadLibrary0(Unknown Source)6     at java.lang.System.loadLibrary(Unknown Source)7     at org.amse.ys.zip.DeflatingDecompressor.
     
      (DeflatingDecompressor.java:7)
     

使用 查看DeflatingDecompressor.dll的依赖关系，发现缺少zlib1.dll, 这时候我想起来下载的zlib发布中还有一个动态库，拷贝到System32文件夹下，再试，果然可以了。

那么这时候为什么呢？经过资料查询才知道VS编译出来的lib文件有静态和动态lib的区别，简单的说：静态lib就是把所有的代码一股脑编译进lib文件中，在使用的时候配合头文件和lib文件就可以直接用了。而动态lib则是伴随着dll生成的，其中只包含了动态加载dll的代码，通过在程序中引用它，就可以省去了显式的调用dll的繁琐。

如何判断一个lib是静态还是动态的呢？我没有找到好的办法，一般来说，静态lib的发布只有两个文件：一个头文件定义了lib中的开放接口，一个.lib文件则是实现的内容；而动态lib的文件发布包含一个头文件，一个dll文件，一个lib文件，往往还有一个def文件来列出dll中的接口。根据这个就可以判断了。

好了，这就是调用没有成功的原因，我本来已经加载的lib是一个静态lib, 其实它是一个动态lib