使用javaAPI进行文件的解压缩

• 前言
• 二、代码

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前言

二、代码

代码如下（示例）：

package com.atguigu.mr.test;

import static org.junit.Assert.*;

import java.io.IOException;
import java.io.InputStream;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
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;
import org.junit.Test;

public class TestCompression {

	@Test
	public void testcompression() throws ClassNotFoundException, IOException {
		
		//解压缩：调用Compressioncodec.createcompressioninputsream	返回一个可以解压缩的输入流
		//压缩：调用Compressioncodec.createcompressionoutputsream	返回一个可以压缩的输出流
	Path file=new Path("D:/悲惨世界.txt");
	String codecClassName="org.apache.hadoop.io.compress.GzipCodec";
	Class<?> codecClass = Class.forName(codecClassName);
	Configuration conf = new Configuration();
	FileSystem fs=FileSystem.get(conf);
	FSDataInputStream inputStream = fs.open(file);
	//确定使用哪种压缩格式compressioncodec
	CompressionCodec codec = (CompressionCodec) ReflectionUtils.newInstance(codecClass, conf);
	FSDataOutputStream outputStream = fs.create(new Path("D:/file"+codec.getDefaultExtension()), true);
	//带压缩的输出流
	CompressionOutputStream createOutputStream = codec.createOutputStream(outputStream);
	IOUtils.copyBytes(inputStream, createOutputStream, conf, true);
	
	}
@Test
public void testdecompression() throws Exception {
	Path file=new Path("D:/file.gz");
	Configuration conf = new Configuration();
	//根据后缀获取文件的额压缩格式
	CompressionCodec codec = new CompressionCodecFactory(conf).getCodec(file);
//创建一个可以解压缩的输入流
	FileSystem fs=FileSystem.get(conf);
	FSDataInputStream is = fs.open(file);
	CompressionInputStream createInputStream = codec.createInputStream(is);
	//创建一个非压缩的输出流
	FSDataOutputStream outputstream = fs.create(new Path("D:/file.txt"), true);
	IOUtils.copyBytes(createInputStream, outputstream, conf, true);
}
}

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