readFile

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import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
/***
 * 
 * @author
 *
 */
public class readFile {
    public static void main(String[] args) throws IOException {
        //創建Configuration實例
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://192.168.1.100:9000");
        //通過配置獲取到文件系統
        FileSystem fs = FileSystem.get(conf);
        //定義要讀取文件所在的HDFS路徑
        Path src=new Path("hdfs://192.168.1.100:9000/user/hadoop/input/core-site.xml");
        //通過文件系統的open()方法得到一個文件輸入流，用於讀取
        FSDataInputStream dis = fs.open(src);
        //用IOUtils下的copyBytes將流中的數據打印輸出到控制台
        IOUtils.copyBytes(dis, System.out, conf);
        //關閉輸入流
        dis.close();
    }
}