CompressionCodec有两个方法可以用于轻松地压缩或解压缩数据。要想对正在被写入一个输出流的数据进行压缩，我们可以使用createOutputStream(OutputStreamout)方法创建一个CompressionOutputStream，将其以压缩格式写入底层的流。相反，要想对从输入流读取而来的数据进行解压缩，则调用createInputStream(InputStreamin)函数，从而获得一个CompressionInputStream，从而从底层的流读取未压缩的数据。
测试一下如下压缩方式

1、压缩

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.io.compress.CompressionOutputStream;
import org.apache.hadoop.util.ReflectionUtils;

public class TestComporess {

    public static void main(String[] args) throws Exception {
        compress("e:/log.txt", "org.apache.hadoop.io.compress.BZip2Codec");
        // compress("e:/log.txt", "org.apache.hadoop.io.compress.GzipCodec");
        // compress("e:/log.txt", "org.apache.hadoop.io.compress.Lz4Codec");
        // compress("e:/test.txt", "org.apache.hadoop.io.compress.DefaultCodec");

    }

    // 压缩测试
    private static void compress(String filename, String method) throws ClassNotFoundException, IOException {

        // 1 获取输入流
        FileInputStream fis = new FileInputStream(new File(filename));

        // 2 获取输出流
        Class classname = Class.forName(method);

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

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

        // 3 把输出流封装成压缩流
        CompressionOutputStream cos = codec.createOutputStream(fos);

        // 4 对拷贝
        IOUtils.copyBytes(fis, cos, 1024 * 1024 * 5, false);

        // 5 关闭资源
        fis.close();
        cos.close();
        fos.close();
    }

}

2、解压缩

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;

public class TestDecompress {

    public static void main(String[] args) throws Exception {
        decompress("e:/log.txt.gz");
    }

    // 解压缩
    private static void decompress(String filename) throws FileNotFoundException, IOException {
        
        // 1 判断是否有解压缩的方法
        CompressionCodecFactory factory = new CompressionCodecFactory(new Configuration());
        CompressionCodec codec = factory.getCodec(new Path(filename));
        
        if (null == codec) {
            System.out.println("not find " + codec);
            return;
        }
        
        // 2 获取输入流
        CompressionInputStream cis = codec.createInputStream(new FileInputStream(filename));
        
        // 3 获取输出流
        FileOutputStream fos = new FileOutputStream(new File(filename + ".decode"));
        
        // 4 流的对拷贝
        IOUtils.copyBytes(cis, fos, 1024*1024*5, false);
        
        // 5 关闭资源
        cis.close();
        fos.close();
        
    }
}

3、Code -> GitHub

https://github.com/liufengji/hadoop_mapreduce.git