Java操作Hdfs

java代码

1.  
   package cn.itcast.hadoop.hdfs;
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3.  
   import java.io.FileInputStream;
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   import java.io.FileNotFoundException;
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   import java.io.FileOutputStream;
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   import java.io.IOException;
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   import java.io.InputStream;
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   import java.io.OutputStream;
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   import java.net.URI;
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    import java.net.URISyntaxException;
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    import org.apache.hadoop.conf.Configuration;
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    import org.apache.hadoop.fs.FileSystem;
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    import org.apache.hadoop.fs.Path;
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    import org.apache.hadoop.io.IOUtils;
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    import org.junit.Before;
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    import org.junit.Test;
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    public class HDFSDemo {
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    FileSystem fs = null;
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    @Before
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    public void init() throws Exception{
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    fs = FileSystem.get(new URI("hdfs://itcast01:9000"), new Configuration(), "root");
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    }
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    @Test
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    public void testUpload() throws Exception{
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    InputStream in = new FileInputStream("/root/install.log");
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    OutputStream out = fs.create(new Path("/log123.log"));
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    IOUtils.copyBytes(in, out, 1024, true);
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    }
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    @Test
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    public void testMkdir() throws IllegalArgumentException, IOException{
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    boolean flag = fs.mkdirs(new Path("/a/aa"));
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    System.out.println(flag);
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    }
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41.  
    @Test
42.  
    public void testDel() throws IllegalArgumentException, IOException{
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    boolean flag = fs.delete(new Path("/a"), true);
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    System.out.println(flag);
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    }
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48.  
     
49.  
    public static void main(String[] args) throws Exception {
50.  
    FileSystem fs = FileSystem.get(new URI("hdfs://itcast01:9000"), new Configuration());
51.  
    InputStream in = fs.open(new Path("/jdk"));
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    OutputStream out = new FileOutputStream("/home/jdk1.7.tar.gz");
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    IOUtils.copyBytes(in, out, 4096, true);
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55.  
    }
56.  
    }

处理连不上hdfs的情况

1、删除tmp

 2、修改配置

修改namenode的地址为具体IP (之前写的localhost)

修改slaves文件,为具体IP

3、 格式化hdfs

hadoop namenode –format

4、启动hdfs

start-dfs.sh

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