尚硅谷大数据技术之Hadoop（MapReduce）（新）第4章 Hadoop数据压缩

4.6 压缩实操案例

4.6.1 数据流的压缩和解压缩

测试一下如下压缩方式：

表4-11

DEFLATE	org.apache.hadoop.io.compress.DefaultCodec
gzip	org.apache.hadoop.io.compress.GzipCodec
bzip2	org.apache.hadoop.io.compress.BZip2Codec

package com.atguigu.mapreduce.compress;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.IOUtils;

import org.apache.hadoop.io.compress.CompressionCodec;

import org.apache.hadoop.io.compress.CompressionCodecFactory;

import org.apache.hadoop.io.compress.CompressionInputStream;

import org.apache.hadoop.io.compress.CompressionOutputStream;

import org.apache.hadoop.util.ReflectionUtils;

public class TestCompress {

public static void main(String[] args) throws Exception {

compress("e:/hello.txt","org.apache.hadoop.io.compress.BZip2Codec");

// decompress("e:/hello.txt.bz2");

}

// 1、压缩

private static void compress(String filename, String method) throws Exception {

// （1）获取输入流

FileInputStream fis = new FileInputStream(new File(filename));

Class codecClass = Class.forName(method);

CompressionCodec codec = (CompressionCodec) ReflectionUtils.newInstance(codecClass, new Configuration());

// （2）获取输出流

FileOutputStream fos = new FileOutputStream(new File(filename + codec.getDefaultExtension()));

CompressionOutputStream cos = codec.createOutputStream(fos);

// （3）流的对拷

IOUtils.copyBytes(fis, cos, 1024*1024*5, false);

// （4）关闭资源

cos.close();

fos.close();

fis.close();

}

// 2、解压缩

private static void decompress(String filename) throws FileNotFoundException, IOException {

// （0）校验是否能解压缩

CompressionCodecFactory factory = new CompressionCodecFactory(new Configuration());

CompressionCodec codec = factory.getCodec(new Path(filename));

if (codec == null) {

System.out.println("cannot find codec for file " + filename);

return;

}

// （1）获取输入流

CompressionInputStream cis = codec.createInputStream(new FileInputStream(new File(filename)));

// （2）获取输出流

FileOutputStream fos = new FileOutputStream(new File(filename + ".decoded"));

// （3）流的对拷

IOUtils.copyBytes(cis, fos, 1024*1024*5, false);

// （4）关闭资源

cis.close();

fos.close();

}

}