RPC网络编程

Java代码操作Hadoop

Java在Windows中，Hadoop在Linux中

先在hadoop pom.xml文件中导入以下几个包

    
        org.apache.hadoop
        hadoop-hdfs
        2.7.6
    
    
        org.apache.hadoop
        hadoop-common
        2.7.6
    
    
        org.apache.hadoop
        hadoop-client
        2.7.6
    

    
        junit
        junit
        4.3
    

public class HadoopAPI {
    FileSystem fs;
    @Before
    public void inti() throws Exception{
        //hadoop配置文件
        Configuration conf = new Configuration();
        conf.set("dfs.replication","1");
        URI uri = new URI("hdfs://master:9000");
        fs= FileSystem.get(uri, conf);
    }

    //创建目录
    @Test
    public void mkdir() throws Exception{
        fs.mkdirs(new Path("/mk"));
    }
    
    //删除
    //true：迭代删除
    @Test
    public void delete() throws  Exception{
        fs.delete(new Path("/student.txt"),false);
    }

    //获取文件或目录
    //list...获取单个   getFile...获取多个
    @Test
    public void list() throws Exception{
        FileStatus[] fs = this.fs.listStatus(new Path("/"));
        for (FileStatus f : fs) {
            System.out.println(f);
            System.out.println(f.getLen());
            System.out.println(f.getBlockSize());
            System.out.println(f.getPath());
            System.out.println(f.getReplication());
        }
    }

    //读取文件
    @Test
    public void open() throws Exception{
        FSDataInputStream open = fs.open(new Path("/student.txt"));
        BufferedReader br = new BufferedReader(new InputStreamReader(open));
        String line;
        while((line=br.readLine())!=null){
            System.out.println(line);
        }
        br.close();
        open.close();
    }

    //写文件
    @Test
    public void create() throws Exception{
        FSDataOutputStream create = fs.create(new Path("/test.txt"));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(create));
        bw.write("你好！");
        bw.newline();
        bw.write("世界！");
        bw.newline();
        bw.close();
        create.close();
    }

    //上传
    @Test
    public void copyFromLocal() throws  Exception{
        Path hdfs =new Path("/");
        Path local =new Path("D:\BigData\ideaProjects\bd13\data\student.txt");
        fs.copyFromLocalFile(local,hdfs);
    }

    //下载
    @Test
    public void copyToLocal() throws Exception{
        Path hdfs=new Path("/test.txt");
        Path local=new Path("D:\BigData\ideaProjects\bd13\data");
       fs.copyToLocalFile(false,hdfs,local,true);
    }
}