dedecms 招聘网站,医疗今科云平台网站建设技术开发,怎么攻击网站,网页设计与网站建设区别转载自 Java压缩技术#xff08;六#xff09; BZIP2——Commons实现
BZip2与GZip有什么渊源#xff0c;我这里不深究。我要说的只是#xff0c;这两种算法#xff0c;你在linux下都可以找到相应的操作命令。GZip 压缩 gzip file 将得到压缩文件file.gz六 BZIP2——Commons实现
BZip2与GZip有什么渊源我这里不深究。我要说的只是这两种算法你在linux下都可以找到相应的操作命令。GZip 压缩 gzip file 将得到压缩文件file.gz同时删除文件file 解压缩 gzip -d file.gz 将得到压缩文件file同时删除文件file.gz BZip2与之相当几乎没有什么差别 BZip2 压缩 bzip2 file 将得到压缩文件file.bz2同时删除文件file 解压缩 bzip2 -d file.bz2 将得到压缩文件file同时删除文件file.bz2 除了命令不同外几乎是一样的再说实现。GZIP是JDK自带的算法实现但BZip2则不曾享受这个待遇。不过强大的Apache坚决不会让这些个在Linux下如鱼得水的算法在Java世界中销声匿迹。Apache在Commons Compress中提供了相应的实现。同时还包括众所周知的tar、cpio、zip等算法实现其中最为丰富的当属zip实现了我继续依葫芦画瓢 BZip2CompressorOutputStream类用于压缩 BZip2CompressorInputStream类用于解压缩 先说压缩实现BZip2CompressorOutputStream只有一个方法用于压缩就是带定长的write方法。简单调用如下文所示
Java代码 /** * 数据压缩 * * param is * param os * throws Exception */ public static void compress(InputStream is, OutputStream os) throws Exception { BZip2CompressorOutputStream gos new BZip2CompressorOutputStream(os); int count; byte data[] new byte[BUFFER]; while ((count is.read(data, 0, BUFFER)) ! -1) { gos.write(data, 0, count); } gos.finish(); gos.flush(); gos.close(); } 与GZip实现有何差别除了换掉了GZIPOutputStream没有任何差别。解压缩就更不用说了BZip2CompressorInputStream提供了一个带定长的read方法。简单调用如下文所示 Java代码/** * 数据解压缩 * * param is * param os * throws Exception */ public static void decompress(InputStream is, OutputStream os) throws Exception { BZip2CompressorInputStream gis new BZip2CompressorInputStream(is); int count; byte data[] new byte[BUFFER]; while ((count gis.read(data, 0, BUFFER)) ! -1) { os.write(data, 0, count); } gis.close(); } 嗯没什么难度
IT这行就是这样只要你肯用心能触类旁通就能融会贯通给一个完整实现 Java代码/** * 2010-4-15 */ package org.zlex.commons.compress.compress; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.InputStream; import java.io.OutputStream; import org.apache.commons.compress.compressors.bzip2.BZip2CompressorInputStream; import org.apache.commons.compress.compressors.bzip2.BZip2CompressorOutputStream; /** * BZip2工具 * * author a hrefmailto:zlex.donglianggmail.com梁栋/a * since 1.0 */ public abstract class BZip2Utils { public static final int BUFFER 1024; public static final CharSequence EXT .bz2; /** * 数据压缩 * * param data * return * throws Exception */ public static byte[] compress(byte[] data) throws Exception { ByteArrayInputStream bais new ByteArrayInputStream(data); ByteArrayOutputStream baos new ByteArrayOutputStream(); // 压缩 compress(bais, baos); byte[] output baos.toByteArray(); baos.flush(); baos.close(); bais.close(); return output; } /** * 文件压缩 * * param file * throws Exception */ public static void compress(File file) throws Exception { compress(file, true); } /** * 文件压缩 * * param file * param delete * 是否删除原始文件 * throws Exception */ public static void compress(File file, boolean delete) throws Exception { FileInputStream fis new FileInputStream(file); FileOutputStream fos new FileOutputStream(file.getPath() EXT); compress(fis, fos); fis.close(); fos.flush(); fos.close(); if (delete) { file.delete(); } } /** * 数据压缩 * * param is * param os * throws Exception */ public static void compress(InputStream is, OutputStream os) throws Exception { BZip2CompressorOutputStream gos new BZip2CompressorOutputStream(os); int count; byte data[] new byte[BUFFER]; while ((count is.read(data, 0, BUFFER)) ! -1) { gos.write(data, 0, count); } gos.finish(); gos.flush(); gos.close(); } /** * 文件压缩 * * param path * throws Exception */ public static void compress(String path) throws Exception { compress(path, true); } /** * 文件压缩 * * param path * param delete * 是否删除原始文件 * throws Exception */ public static void compress(String path, boolean delete) throws Exception { File file new File(path); compress(file, delete); } /** * 数据解压缩 * * param data * return * throws Exception */ public static byte[] decompress(byte[] data) throws Exception { ByteArrayInputStream bais new ByteArrayInputStream(data); ByteArrayOutputStream baos new ByteArrayOutputStream(); // 解压缩 decompress(bais, baos); data baos.toByteArray(); baos.flush(); baos.close(); bais.close(); return data; } /** * 文件解压缩 * * param file * throws Exception */ public static void decompress(File file) throws Exception { decompress(file, true); } /** * 文件解压缩 * * param file * param delete * 是否删除原始文件 * throws Exception */ public static void decompress(File file, boolean delete) throws Exception { FileInputStream fis new FileInputStream(file); FileOutputStream fos new FileOutputStream(file.getPath().replace(EXT, )); decompress(fis, fos); fis.close(); fos.flush(); fos.close(); if (delete) { file.delete(); } } /** * 数据解压缩 * * param is * param os * throws Exception */ public static void decompress(InputStream is, OutputStream os) throws Exception { BZip2CompressorInputStream gis new BZip2CompressorInputStream(is); int count; byte data[] new byte[BUFFER]; while ((count gis.read(data, 0, BUFFER)) ! -1) { os.write(data, 0, count); } gis.close(); } /** * 文件解压缩 * * param path * throws Exception */ public static void decompress(String path) throws Exception { decompress(path, true); } /** * 文件解压缩 * * param path * param delete * 是否删除原始文件 * throws Exception */ public static void decompress(String path, boolean delete) throws Exception { File file new File(path); decompress(file, delete); } } 对应再来个测试用例测试用例如下所示 Java代码 /** * 2010-4-13 */ package org.zlex.commons.compress.compress; import static org.junit.Assert.assertEquals; import java.io.DataInputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import org.junit.Test; /** * BZip2 * * author a hrefmailto:zlex.donglianggmail.com梁栋/a * since 1.0 */ public class BZip2UtilsTest { private String inputStr zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org; Test public final void testDataCompress() throws Exception { byte[] input inputStr.getBytes(); System.err.println(原文:\t inputStr); System.err.println(长度:\t input.length); byte[] data BZip2Utils.compress(input); System.err.println(压缩后:\t); System.err.println(长度:\t data.length); byte[] output BZip2Utils.decompress(data); String outputStr new String(output); System.err.println(解压缩后:\t outputStr); System.err.println(长度:\t output.length); assertEquals(inputStr, outputStr); } Test public final void testFileCompress() throws Exception { FileOutputStream fos new FileOutputStream(d:/f.txt); fos.write(inputStr.getBytes()); fos.flush(); fos.close(); BZip2Utils.compress(d:/f.txt); BZip2Utils.decompress(d:/f.txt.bz2); File file new File(d:/f.txt); FileInputStream fis new FileInputStream(file); DataInputStream dis new DataInputStream(fis); byte[] data new byte[(int) file.length()]; dis.readFully(data); fis.close(); String outputStr new String(data); assertEquals(inputStr, outputStr); } } 虽然两种算法在代码实现上几乎没有什么差别但在压缩上想要看到效果还真让我费了点事控制台输出如下所示 引用原文: zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org长度: 529 压缩后: 长度: 76 解压缩后: zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org,zlexzlex.org,snowolfzlex.org,zlex.snowolfzlex.org长度: 529 529字节--76字节 GZIP本身不需要太长的内容经过压缩就能体现出压缩效果而BZip2则需要压缩很长的内容时才能体现其压缩效果这说明BZip2更适合大数据压缩Commons Compress不仅支持BZip2算法实现同时也支持GZip算法实现。对于GZip算法实现与Java原生实现基本上没有什么差别。其源代码分析仅仅是做了简单的包装。 不过有必要提及的一点是Commons Compress为压缩GZip和BZip2构建了压缩算法工厂类
CompressorStreamFactory
。通过这个类可以方便的构建GZip和BZip2的输入输出流关键字分别为“gz”和“bzip2”。 GZip Java代码 // GzipCompressorInputStream CompressorInputStream gzipIn new CompressorStreamFactory() .createCompressorInputStream(gz, is); // GzipCompressorOutputStream CompressorOutputStream gzipOut new CompressorStreamFactory() .createCompressorOutputStream(gz, os); BZip2 Java代码 // BZip2CompressorInputStream CompressorInputStream bzip2In new CompressorStreamFactory() .createCompressorInputStream(bzip2, is); // BZip2CompressorOutputStream CompressorOutputStream bzip2Out new CompressorStreamFactory() .createCompressorOutputStream(bzip2, os); GZip和BZip2在算法实现步骤上基本上没有什么差别如果有必要统一可按上述代码实现BZip2Utils.rar (1.8 KB)下载次数: 374
