HDFS Java API操作——《大数据技术原理与应用（第3版）》期末复习

目录

HDFS Java API操作

这里使用Junit包的@Before、@Test方法进行调试测试

创建目录

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fs.mkdirs()

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//第一步，获取Hadoop FileSystem对象privateFileSystem fs =null;//初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException{/*
        * new URI("hdfs:192.168.206.3:9000"):连接Hadoop
        * Configuration() : 使用Hadoop默认配置
        * "root":登录用户
        */Configuration conf =newConfiguration();
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),conf);}//创建目录@TestpublicvoidtestMkdir(){boolean flag = fs.mkdirs(newPath("/javaAPI/mk/dir1/dir2"));System.out.println(flag ?"创建成功":"创建失败");}

显示目录列表

//第一步，获取Hadoop FileSystem对象privateFileSystem fs =null;privateList<String> hdfsPathsLists;//第二步,初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException,IOException,InterruptedException{
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),newConfiguration(),"root");}//显示目录@TestpublicvoidgetDirList()throwsIOException{//初始化存放目录的List
        hdfsPathsLists =newArrayList<String>();//调用获取目录方法getHdfspaths(newPath("/"));//循环输入结果for(String p:hdfsPathsLists){System.out.println(p);}}//获取目录方法privatevoidgetHdfspaths(Path path)throwsIOException{/*递归方法便利获取目录及目录下文件*/FileStatus[] dirs = fs.listStatus(path);for(FileStatus s:dirs){
            hdfsPathsLists.add(s.getPath().toString());if(s.isDirectory()){getHdfspaths(s.getPath());}}}@Afterpublicvoidclose()throwsIOException{
        fs.close();}

删除目录

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fs.deleteOnExit()

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//第一步,获取Hadoop FileSystem对象privateFileSystem fs =null;//第二步,初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException,IOException,InterruptedException{
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),newConfiguration(),"root");}//删除目录@TestpublicvoidtestRMdir()throwsIOException{boolean flag = fs.deleteOnExit(newPath("/javaAPI/mk/dir1/dir2"));System.out.println(flag ?"删除成功":"删除失败");}

判断文件存在

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fs.exists()

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//第一步,获取Hadoop FileSystem对象privateFileSystem fs =null;//第二步,初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException,IOException,InterruptedException{
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),newConfiguration(),"root");}//判断文件存在@TestpublicvoidtestExistsFile()throwsIOException{String src ="hdfs://192.168.206.3:9000/a.txt";boolean b = fs.exists(newPath(src));if(b){System.out.println(b +"-exists");}else{System.out.println(b +"-not exists");}}

目录和文件判断

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fs.isDirectory

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fs.isFile

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//第一步,获取Hadoop FileSystem对象privateFileSystem fs =null;//第二步,初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException,IOException,InterruptedException{
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),newConfiguration(),"root");}//目录和文件判断@TestpublicvoidtestfilesFile()throwsIOException{String src ="hdfs://192.168.206.3:9000/a.txt";boolean b = fs.isDirectory(newPath(src));if(b){System.out.println("是目录鸭");}elseif(fs.isFile(newPath(src))){System.out.println("是文件鸭");}else{System.out.println("不确定");}}

重命名文件

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fs.rename

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//第一步,获取Hadoop FileSystem对象privateFileSystem fs =null;//第二步,初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException,IOException,InterruptedException{
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),newConfiguration(),"root");}//重命名文件@TestpublicvoidtestRenameFile()throwsIOException{String src ="hdfs://192.168.206.3:9000/a.txt";String hdfsDst ="hdfs://192.168.206.3:9000/b.txt";
        fs.rename(newPath(src),newPath(hdfsDst));System.out.println("重命名成功");}

上传文件

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fs.copyFromLocalFile

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//第一步,获取Hadoop FileSystem对象privateFileSystem fs =null;//第二步,初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException,IOException,InterruptedException{
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),newConfiguration(),"root");}//上传文件@TestpublicvoidtestUploadFile()throwsIOException{String src ="/simple/local.txt";String hdfsDst ="/javaAPI";
        fs.copyFromLocalFile(newPath(src),newPath(hdfsDst));System.out.println("upload success");}

文件移动

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fs.moveToLocalFile

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fs.moveFromLocalFile

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//第一步,获取Hadoop FileSystem对象privateFileSystem fs =null;//第二步,初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException,IOException,InterruptedException{
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),newConfiguration(),"root");}//文件移动/*
    * 对hdfs上的文件进行移动到本地
    * */@TestpublicvoidtestmovetoLocalFile()throwsIOException{String src ="hdfs://192.168.206.3:9000/a.txt";String desc ="/root/";
        fs.moveToLocalFile(newPath(src),newPath(desc));System.out.println("成功移动");}/*
     * 对本地上的文件进行移动到hdfs
     * 此时使用的是moveFromLocalFile，所以会将本地的移到hdfs,即本地不存在了。
     * */@TestpublicvoidtestmovetoHdfsFile()throwsIOException{String src ="/root/b.txt";String desc ="hdfs://192.168.206.3:9000/javaAPI";
        fs.moveFromLocalFile(newPath(src),newPath(desc));System.out.println("成功移动");}

文件下载

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fs.copyToLocalFile

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//第一步,获取Hadoop FileSystem对象privateFileSystem fs =null;//第二步,初始化环境变量@Beforepublicvoidinit()throwsURISyntaxException,IOException,InterruptedException{
        fs =FileSystem.get(newURI("hdfs://192.168.206.3:9000"),newConfiguration(),"root");}/*
    * 文件下载到本地
    * */@TestpublicvoidtestDownloadFile()throwsIOException{String src ="/javaAPI/mk/dir1/a.txt";String hdfsDst ="/root/";
        fs.copyToLocalFile(newPath(src),newPath(hdfsDst));System.out.println("下载成功");}