HDFS常用API操作 和 HDFS的I/O流操作

前置操作

创建maven工程，修改pom.xml文件：

<project xmlns="http://maven.apache.org/pom/4.0.0" xmlns:xsi="http://www.w3.org/2001/xmlschema-instance" xsi:schemalocation="http://maven.apache.org/pom/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelversion>4.0.0</modelversion>
  <groupid>com.mcq</groupid>
  <artifactid>hdfs-001</artifactid>
  <version>0.0.1-snapshot</version>
  <dependencies>
		<dependency>
			<groupid>junit</groupid>
			<artifactid>junit</artifactid>
			<version>release</version>
		</dependency>
		<dependency>
			<groupid>org.apache.logging.log4j</groupid>
			<artifactid>log4j-core</artifactid>
			<version>2.8.2</version>
		</dependency>
		<dependency>
			<groupid>org.apache.hadoop</groupid>
			<artifactid>hadoop-common</artifactid>
			<version>2.7.2</version>
		</dependency>
		<dependency>
			<groupid>org.apache.hadoop</groupid>
			<artifactid>hadoop-client</artifactid>
			<version>2.7.2</version>
		</dependency>
		<dependency>
			<groupid>org.apache.hadoop</groupid>
			<artifactid>hadoop-hdfs</artifactid>
			<version>2.7.2</version>
		</dependency>
		<dependency>
			<groupid>jdk.tools</groupid>
			<artifactid>jdk.tools</artifactid>
			<version>1.8</version>
			<scope>system</scope>
			<systempath>${java_home}/lib/tools.jar</systempath>
		</dependency>
</dependencies>

</project>

在resources添加一个file：log4j.properties：

log4j.rootlogger=info, stdout
log4j.appender.stdout=org.apache.log4j.consoleappender
log4j.appender.stdout.layout=org.apache.log4j.patternlayout
log4j.appender.stdout.layout.conversionpattern=%d %p [%c] - %m%n
log4j.appender.logfile=org.apache.log4j.fileappender
log4j.appender.logfile.file=target/spring.log
log4j.appender.logfile.layout=org.apache.log4j.patternlayout
log4j.appender.logfile.layout.conversionpattern=%d %p [%c] - %m%n

 

api操作

hdfs的命令和linux极其相似，可以类比记忆，在这里列出一些java api操作：

package com.mcq;

import java.io.ioexception;
import java.net.uri;
import java.net.urisyntaxexception;

import org.apache.hadoop.conf.configuration;
import org.apache.hadoop.fs.blocklocation;
import org.apache.hadoop.fs.filestatus;
import org.apache.hadoop.fs.filesystem;
import org.apache.hadoop.fs.locatedfilestatus;
import org.apache.hadoop.fs.path;
import org.apache.hadoop.fs.remoteiterator;
import org.junit.test;

public class hdfsclient {
	public static void main(string[] args) throws ioexception, interruptedexception, urisyntaxexception {
		configuration conf = new configuration();
		// c.set("fs.defaultfs", "hdfs://hadoop103:9000");
		// filesystem fs = filesystem.get(c);
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), conf, "mcq");
		fs.mkdirs(new path("/ppqq"));
		fs.close();
		system.out.println("over");
	}

	@test // 文件上传
	public void testcopyfromlocalfile()
			throws illegalargumentexception, ioexception, interruptedexception, urisyntaxexception {
		configuration conf = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), conf, "mcq");
		fs.copyfromlocalfile(new path("d:/banzhang.txt"), new path("/banzhang.txt"));
		fs.close();
		system.out.println("over");
	}

	@test // 文件下载
	public void testcopytolocalfile() throws ioexception, interruptedexception, urisyntaxexception {
		configuration conf = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), conf, "mcq");
		fs.copytolocalfile(false, new path("/banzhang.txt"), new path("d:/hadoop test/banhua.txt"), true);
		// 第一个false表示不剪切，最后一个true表示本地，不产生crc文件

		fs.close();
		system.out.println("over");
	}

	@test // 文件删除
	public void testdelete() throws ioexception, interruptedexception, urisyntaxexception {
		configuration conf = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), conf, "mcq");
		fs.delete(new path("/0811"), true); // 是否递归删除
		fs.close();
		system.out.println("over");
	}

	@test // 文件更名
	public void testrename() throws ioexception, interruptedexception, urisyntaxexception {
		configuration conf = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), conf, "mcq");
		fs.rename(new path("/banzhang.txt"), new path("/lala.txt"));
		fs.close();
		system.out.println("over");
	}

	@test
	public void testlistfiles() throws ioexception, interruptedexception, urisyntaxexception {

		// 1获取文件系统
		configuration configuration = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), configuration, "mcq");

		// 2 获取文件详情
		remoteiterator<locatedfilestatus> listfiles = fs.listfiles(new path("/"), true);

		while (listfiles.hasnext()) {
			locatedfilestatus status = listfiles.next();

			// 输出详情
			// 文件名称
			system.out.println(status.getpath().getname());
			// 长度
			system.out.println(status.getlen());
			// 权限
			system.out.println(status.getpermission());
			// 分组
			system.out.println(status.getgroup());

			// 获取存储的块信息
			blocklocation[] blocklocations = status.getblocklocations();

			for (blocklocation blocklocation : blocklocations) {

				// 获取块存储的主机节点
				string[] hosts = blocklocation.gethosts();

				for (string host : hosts) {
					system.out.println(host);
				}
			}

			system.out.println("-----------分割线----------");
		}

		// 3 关闭资源
		fs.close();
	}
	
	@test
	public void testliststatus() throws ioexception, interruptedexception, urisyntaxexception{
			
		// 1 获取文件配置信息
		configuration configuration = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), configuration, "mcq");
			
		// 2 判断是文件还是文件夹
		filestatus[] liststatus = fs.liststatus(new path("/"));
			
		for (filestatus filestatus : liststatus) {
			
			// 如果是文件
			if (filestatus.isfile()) {
					system.out.println("f:"+filestatus.getpath().getname());
				}else {
					system.out.println("d:"+filestatus.getpath().getname());
				}
			}
			
		// 3 关闭资源
		fs.close();
	}
}

 i/o流操作

上面的api操作 hdfs系统都是框架封装好的，如果我们想自己实现上述api操作可以采用io流的方式实现数据的上传和下载。

 

package com.mcq;

import java.io.file;
import java.io.fileinputstream;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.net.uri;
import java.net.urisyntaxexception;

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.yarn.api.records.url;
import org.junit.test;

public class hdfsio {
	//文件上传
	@test
	public void putfiletohdfs() throws ioexception, interruptedexception, urisyntaxexception {

		// 1 获取文件系统
		configuration configuration = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), configuration, "mcq");

		// 2 创建输入流
		fileinputstream fis = new fileinputstream(new file("d:/banzhang.txt"));

		// 3 获取输出流
		fsdataoutputstream fos = fs.create(new path("/xiaocao.txt"));

		// 4 流对拷
		ioutils.copybytes(fis, fos, configuration);

		// 5 关闭资源
		ioutils.closestream(fos);
		ioutils.closestream(fis);
		fs.close();
	}
	// 文件下载
	@test
	public void getfilefromhdfs() throws ioexception, interruptedexception, urisyntaxexception{

		// 1 获取文件系统
		configuration configuration = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), configuration, "mcq");
			
		// 2 获取输入流
		fsdatainputstream fis = fs.open(new path("/banhua.txt"));
			
		// 3 获取输出流
		fileoutputstream fos = new fileoutputstream(new file("d:/banhua.txt"));
			
		// 4 流的对拷
		ioutils.copybytes(fis, fos, configuration);
			
		// 5 关闭资源
		ioutils.closestream(fos);
		ioutils.closestream(fis);
		fs.close();
	}
	//定位文件读取
	//（1）下载第一块
	@test
	public void readfileseek1() throws ioexception, interruptedexception, urisyntaxexception{

		// 1 获取文件系统
		configuration configuration = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), configuration, "mcq");
			
		// 2 获取输入流
		fsdatainputstream fis = fs.open(new path("/hadoop-2.7.2.tar.gz"));
			
		// 3 创建输出流
		fileoutputstream fos = new fileoutputstream(new file("e:/hadoop-2.7.2.tar.gz.part1"));
			
		// 4 流的拷贝
		byte[] buf = new byte[1024];
			
		for(int i =0 ; i < 1024 * 128; i++){
			fis.read(buf);
			fos.write(buf);
		}
			
		// 5关闭资源
		ioutils.closestream(fis);
		ioutils.closestream(fos);
	fs.close();
	}
	//（2）下载第二块
	@test
	public void readfileseek2() throws ioexception, interruptedexception, urisyntaxexception{

		// 1 获取文件系统
		configuration configuration = new configuration();
		filesystem fs = filesystem.get(new uri("hdfs://hadoop103:9000"), configuration, "mcq");
			
		// 2 打开输入流
		fsdatainputstream fis = fs.open(new path("/hadoop-2.7.2.tar.gz"));
			
		// 3 定位输入数据位置
		fis.seek(1024*1024*128);
			
		// 4 创建输出流
		fileoutputstream fos = new fileoutputstream(new file("e:/hadoop-2.7.2.tar.gz.part2"));
			
		// 5 流的对拷
		ioutils.copybytes(fis, fos, configuration);
			
		// 6 关闭资源
		ioutils.closestream(fis);
		ioutils.closestream(fos);
	}
}