Java压缩技术(六) BZIP2 |
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Java压缩技术(一) ZLib Java压缩技术(二) ZIP压缩——Java原生实现 Java压缩技术(三) ZIP解压缩——Java原生实现 Java压缩技术(四) GZIP——Java原生实现 Java压缩技术(五) GZIP相关——浏览器解析 Java压缩技术(六) BZIP2——Commons实现 Java压缩技术(七) TAR——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 将得到压缩文件.gz,同时删除文件 解压缩 gzip -d .gz 将得到压缩文件,同时删除文件.gz BZip2与之相当,几乎没有什么差别~~ BZip2 压缩 bzip2 将得到压缩文件.bz2,同时删除文件 解压缩 bzip2 -d .bz2 将得到压缩文件,同时删除文件.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 梁栋 * @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 梁栋 * @since 1.0 */ public class BZip2UtilsTest { private String inputStr = "[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]"; @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: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected] 长度: 529 压缩后: 长度: 76 解压缩后: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected] 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! |
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