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Java压缩技术（三） ZIP解压缩——Java原生实现
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轉(zhuǎn)載自? ?Java壓縮技術(shù)（三） ZIP解壓縮——Java原生實現(xiàn)
解壓縮與壓縮運作方式相反，原理大抵相同，由ZipInputStream通過read方法對數(shù)據(jù)解壓，同時需要通過CheckedInputStream設(shè)置冗余校驗碼，如：?
Java代碼??
CheckedInputStream?cis?=?new?CheckedInputStream(new?FileInputStream(??????????srcFile),?new?CRC32());????ZipInputStream?zis?=?new?ZipInputStream(cis);??
需要注意的是，在構(gòu)建解壓文件時，需要考慮目錄的自動創(chuàng)建，這里通過遞歸方式逐層創(chuàng)建父目錄，如下所示：?
Java代碼??
??????????private?static?void?fileProber(File?dirFile)?{????????File?parentFile?=?dirFile.getParentFile();??????if?(!parentFile.exists())?{??????????????????????fileProber(parentFile);????????????parentFile.mkdir();??????}????}??
在壓縮的時候，我們是將一個一個文件作為壓縮添加項（ZipEntry）添加至壓縮包中，解壓縮就要將一個一個壓縮項從壓縮包中提取出來，如下所示：?
Java代碼??
??????????private?static?void?decompress(File?destFile,?ZipInputStream?zis)??????????throws?Exception?{????????ZipEntry?entry?=?null;??????while?((entry?=?zis.getNextEntry())?!=?null)?{??????????????????????String?dir?=?destFile.getPath()?+?File.separator?+?entry.getName();????????????File?dirFile?=?new?File(dir);??????????????????????fileProber(dirFile);????????????????if?(entry.isDirectory()){??????????????????dirFile.mkdirs();??????????????}?else?{??????????????decompressFile(dirFile,?zis);??????????????}????????????????zis.closeEntry();??????}??}??
最核心的解壓縮實現(xiàn)，其實與壓縮實現(xiàn)非常相似，代碼如下所示：?
Java代碼??
??????????private?static?void?decompressFile(File?destFile,?ZipInputStream?zis)??????????throws?Exception?{????????BufferedOutputStream?bos?=?new?BufferedOutputStream(??????????????new?FileOutputStream(destFile));????????int?count;??????byte?data[]?=?new?byte[BUFFER];??????while?((count?=?zis.read(data,?0,?BUFFER))?!=?-1)?{??????????bos.write(data,?0,?count);??????}????????bos.close();??}??
來個完整的解壓縮實現(xiàn)，代碼如下：?
Java代碼??
????package?org.zlex.commons.io;????import?java.io.BufferedInputStream;??import?java.io.BufferedOutputStream;??import?java.io.File;??import?java.io.FileInputStream;??import?java.io.FileOutputStream;??import?java.util.zip.CRC32;??import?java.util.zip.CheckedInputStream;??import?java.util.zip.CheckedOutputStream;??import?java.util.zip.ZipEntry;??import?java.util.zip.ZipInputStream;??import?java.util.zip.ZipOutputStream;???????????public?class?ZipUtils?{????????public?static?final?String?EXT?=?".zip";??????private?static?final?String?BASE_DIR?=?"";??????private?static?final?String?PATH?=?File.separator;??????private?static?final?int?BUFFER?=?1024;?????????????????????public?static?void?decompress(String?srcPath)?throws?Exception?{??????????File?srcFile?=?new?File(srcPath);????????????decompress(srcFile);??????}???????????????????public?static?void?decompress(File?srcFile)?throws?Exception?{??????????String?basePath?=?srcFile.getParent();??????????decompress(srcFile,?basePath);??????}????????????????????public?static?void?decompress(File?srcFile,?File?destFile)?throws?Exception?{????????????CheckedInputStream?cis?=?new?CheckedInputStream(new?FileInputStream(??????????????????srcFile),?new?CRC32());????????????ZipInputStream?zis?=?new?ZipInputStream(cis);????????????decompress(destFile,?zis);????????????zis.close();????????}????????????????????public?static?void?decompress(File?srcFile,?String?destPath)??????????????throws?Exception?{??????????decompress(srcFile,?new?File(destPath));????????}??????????????????????public?static?void?decompress(String?srcPath,?String?destPath)??????????????throws?Exception?{????????????File?srcFile?=?new?File(srcPath);??????????decompress(srcFile,?destPath);??????}??????????????????????private?static?void?decompress(File?destFile,?ZipInputStream?zis)??????????????throws?Exception?{????????????ZipEntry?entry?=?null;??????????while?((entry?=?zis.getNextEntry())?!=?null)?{??????????????????????????????String?dir?=?destFile.getPath()?+?File.separator?+?entry.getName();????????????????File?dirFile?=?new?File(dir);??????????????????????????????fileProber(dirFile);????????????????if?(entry.isDirectory())?{??????????????????dirFile.mkdirs();??????????????}?else?{??????????????????decompressFile(dirFile,?zis);??????????????}????????????????zis.closeEntry();??????????}??????}??????????????????????private?static?void?fileProber(File?dirFile)?{????????????File?parentFile?=?dirFile.getParentFile();??????????if?(!parentFile.exists())?{??????????????????????????????fileProber(parentFile);????????????????parentFile.mkdir();??????????}????????}??????????????????????private?static?void?decompressFile(File?destFile,?ZipInputStream?zis)??????????????throws?Exception?{????????????BufferedOutputStream?bos?=?new?BufferedOutputStream(??????????????????new?FileOutputStream(destFile));????????????int?count;??????????byte?data[]?=?new?byte[BUFFER];??????????while?((count?=?zis.read(data,?0,?BUFFER))?!=?-1)?{??????????????bos.write(data,?0,?count);??????????}????????????bos.close();??????}????}??
其實，理解了ZIP的工作原理，這些代碼看起來很好懂！
?
把剛才做的壓縮文件再用上述代碼解開看看，測試用例如下：?
Java代碼??
????package?org.zlex.commons.io;????import?static?org.junit.Assert.*;????import?org.junit.Test;???????????public?class?ZipUtilsTest?{????????????????@Test??????public?void?test()?throws?Exception?{????????????????????ZipUtils.decompress("d:\\f.txt.zip",?"d:\\ff");????????????????????ZipUtils.decompress("d:\\fd.zip");??????}????}??
完整代碼詳見附件！
java原生的ZIP實現(xiàn)雖然在壓縮時會因與系統(tǒng)字符集不符產(chǎn)生中文亂碼，但在解壓縮后，字符集即可恢復(fù)。?
除了java原生的ZIP實現(xiàn)外，commons和ant也提供了相應(yīng)的ZIP算法實現(xiàn)，有機會我再一一介紹！
- ZipUtils.rar?(2.1 KB)
- 下載次數(shù): 526
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