【Hadoop】——JavaAPI操作

一、windows客户端准备 <1>双击安装hadoop依赖 <2>放在非中文路径下，双击winutils.exe进行安装

如果安装错误，先安装微软运行库

<3>新建Java Maven 工程 <4>maven坐标

    
        org.apache.hadoop
        hadoop-client
        3.1.3
    
    
        junit
        junit
        4.12
    
    
        org.slf4j
        slf4j-log4j12
        1.7.30
    

<5>在sre/main/resources下新建log4j.properties配置文件

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

<6>新建类 HdfsClient 二、API操作 <1>创建文件夹

package com.demo.hdfs;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

public class HdfsClient {
    private FileSystem fs;
    @Before
    public void init() throws URISyntaxException, InterruptedException, IOException {
        //连接集群nn地址
        URI uri = new URI("hdfs://hadoop102:8020");
        //创建一个配置文件
        Configuration configuration = new Configuration();
        //用户
        String user = "root";
        //获取客户端对象
        fs = FileSystem.get(uri, configuration, user);
    }
    @After
    public void close() throws IOException {
        //关闭资源
        fs.close();
    }
    @Test
    public void testMkdir() throws IOException {
        //创建一个文件夹
        fs.mkdirs(new Path("/apipath1"));
    }
}

<2>上传

//上传
@Test
public void testPut() throws IOException {
    //参数1 ：是否删除元数据
    //参数2： 是否允许覆盖
    //参数3： 目的路径
    fs.copyFromLocalFile(false, true, new Path("E:\study\BigData\Hadoop\脚本\myhadoop.sh"), new Path("hdfs://hadoop102/code"));
}

<3>下载

//下载
@Test
public void testGet() throws IOException {
    //参数1 ：是否删除原数据
    //参数2： 目的路径
    //参数3： 原文件路径
    //参数4：是否进行本地校验 ，false 开启，ture 关闭
    fs.copyToLocalFile(false, new Path("hdfs://hadoop102/code/myhadoop.sh"), new Path("E:\"), true);
}

.xxx.crc文件是一种校验方法

<4>删除

//删除
@Test
public void testRm() throws IOException {
    //参数1 ：目的路径
    //参数2： 是否递归删除
        
    //1. 删除文件
    //fs.delete(new Path("hdfs://hadoop102/code/myhadoop.sh"), true);
    //2. 删除空目录
    //fs.delete( new Path("hdfs://hadoop102/code/code1"), true);

    //3. 删除非空目录,如果不是递归删除，则报错
    fs.delete(new Path("hdfs://hadoop102/code/code2"), true);
}

<5>文件更名和移动

//文件更名和移动
@Test
public void testMv() throws IOException {
    //参数1 ：原文件路径
    //参数2： 目的文件路径

    //1.文件名称更改
    //fs.rename(new Path("hdfs://hadoop102/code/myhadoop.sh"), new Path("hdfs://hadoop102/code/myhadoop_rename.sh"));

    //2.文件移动并修改
    //fs.rename(new Path("hdfs://hadoop102/code/myhadoop_rename.sh"), new Path("hdfs://hadoop102/myhadoop_remove_and_rename.sh"));

    //3. 目录更名
    fs.rename(new Path("hdfs://hadoop102/code"), new Path("hdfs://hadoop102/code_rename"));
    }

<6>文件详细信息查看

查看文件名称、权限、长度、块信息

//文件详细信息查看
@Test
public void testFileDetail() throws IOException {
    //参数1 ：路径
    //参数2： 目的文件路径

    //获取所有文件信息
    RemoteIterator listFiles = fs.listFiles(new Path("hdfs://hadoop102/"), true);
    //遍历文件信息
    while (listFiles.hasNext()) {
        LocatedFileStatus fileStatus = listFiles.next();
        System.out.println("-----------------------------------------");
        System.out.println(fileStatus.toString());
        System.out.println("-----------------------------------------");
    }
}

toString方法

public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(this.getClass().getSimpleName());
        sb.append("{");
        sb.append("path=" + this.path);
        sb.append("; isDirectory=" + this.isdir);
        if (!this.isDirectory()) {
            sb.append("; length=" + this.length);
            sb.append("; replication=" + this.block_replication);
            sb.append("; blocksize=" + this.blocksize);
        }

        sb.append("; modification_time=" + this.modification_time);
        sb.append("; access_time=" + this.access_time);
        sb.append("; owner=" + this.owner);
        sb.append("; group=" + this.group);
        sb.append("; permission=" + this.permission);
        sb.append("; isSymlink=" + this.isSymlink());
        if (this.isSymlink()) {
            try {
                sb.append("; symlink=" + this.getSymlink());
            } catch (IOException var3) {
                throw new RuntimeException("Unexpected exception", var3);
            }
        }

        sb.append("; hasAcl=" + this.hasAcl());
        sb.append("; isEncrypted=" + this.isEncrypted());
        sb.append("; isErasureCoded=" + this.isErasureCoded());
        sb.append("}");
        return sb.toString();
}

<7>文件和文件夹判断

//判断是文件夹还是文件
@Test
public void testFile() throws IOException {
        //获取所有文件信息
        FileStatus[] fileStatuses = fs.listStatus(new Path("hdfs://hadoop102/"));
        //遍历文件信息
        for (FileStatus fileStatus : fileStatuses) {
            if (fileStatus.isFile()) {
                System.out.println("this is file--" + fileStatus.toString());
                System.out.println("-----------------------------------------");
            } else {
                System.out.println("this is path--" + fileStatus.toString());
                System.out.println("-----------------------------------------");
            }
        }
}