HDFS Java Client對hdfs檔案增刪查改

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 step1:增加依賴pom.xml          ...     <!-- https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-common -->           <dependency>                <groupId>org.apache.hadoop</groupId>                <artifactId>hadoop-common</artifactId>                <version>2.2.0</version>                <exclusions>                     <exclusion>                           <artifactId>jdk.tools</artifactId>                           <groupId>jdk.tools</groupId>                     </exclusion>                </exclusions>           </dependency>           <dependency>                <groupId>org.apache.hadoop</groupId>                <artifactId>hadoop-hdfs</artifactId>                <version>2.2.0</version>           </dependency>          ...   step2: 拷貝設定檔‘hdfs-site.xml’和‘core-site.xml’ step3:測試代碼

package cjkjcn.demo.hadoop.hdfs;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.util.LinkedList;import java.util.List;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.FSDataInputStream;import org.apache.hadoop.fs.FileSystem;import org.apache.hadoop.fs.Path;/** * * @author junhong * * 2017年5月18日 */public class HDFSDao {     private static Configuration conf = new Configuration();     private FileSystem hdfs;     final static String ROOT_PATH = "/user";     public HDFSDao() {           conf.addResource("hdfs-site.xml");           conf.addResource("core-site.xml");           try {                hdfs = FileSystem.get(conf); // 初始化hdfs           } catch (IOException e) {                e.printStackTrace();           }           System.out.println("param size=" + conf.size());     }     /**      * 掃描測試檔案是否存在      */     public void scanFiles() {           try {                Path path = new Path(ROOT_PATH);                System.out.println(hdfs.exists(path));           } catch (IOException e) {                e.printStackTrace();           }     }     /**      * 按行讀取文字檔      * @param file      * @return      */     public List<String> lines(String file) {           List<String> list = new LinkedList<>();           Path f = new Path(file);           try {                FSDataInputStream input = hdfs.open(f);                InputStreamReader inr = new InputStreamReader(input);                BufferedReader read = new BufferedReader(inr);                String line;                while ((line = read.readLine()) != null) {                     list.add(line);                }           } catch (IOException e) {                e.printStackTrace();           }           return list;     }}

 

  注意: 1）若缺少依賴            <dependency>                <groupId>org.apache.hadoop</groupId>                <artifactId>hadoop-hdfs</artifactId>                <version>2.2.0</version>           </dependency> 將導致如下錯誤！！ java.io.Exception: No FileSystem for scheme: hdfs  2）測試寫檔案或者建立目錄方法介面時，可能會出現許可權問題Pemission denied for test 

HDFS Java Client對hdfs檔案增刪查改