//副本测试
@Test
public void testReplication(){
    //System.out.println(configuration.get("dfs.replication"));
    //configuration.get("dfs.replication");
    System.out.println(configuration.get("dfs.replication"));
}

报错，空指针异常

我好像没有重新声明Configuration啊，为什么会空呢

package com.immoc.bigdata.hadoop.hdfs;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.net.URI;

/**

• 使用java API操作HDFS文件系统

• 关键点：

• 1)创建Configuration

• 2)获取FileSystem

• 3)你的HDFS API操作
  */
  public class HDFSAPP {

  //虚拟机IP192.168.1.127
  //public static final String HDFS_PATH = “hdfs://hadoop000:8020”;

  public static final String HDFS_PATH = “hdfs://192.168.1.127:8020”;
  FileSystem fileSystem = null;
  Configuration configuration = null;

  @Before
  public void setUp()throws Exception{
  System.out.println(“setUp_____”);

   Configuration configuration=new Configuration();
   //configuration.set("dfs.replication","1");
  
   //configuration.set("dfs.client.use.datanode.hostname", "true");
   /**
    * 构造一个访问指定HDFS系统的客户端对象
    * 第一个参数：HDFS的URI
    * 第二个参数：客户端指定的配置参数
    * 第三个参数：客户端的身份，即用户名
    */
  
   fileSystem=FileSystem.get(new URI(HDFS_PATH),configuration,"hadoop");
  

  }

  //创建HDFS文件夹
  @Test
  public void mkdir() throws Exception {
  Path path=new Path("/hdfsapi/test");
  fileSystem.mkdirs(path);
  //fileSystem.mkdirs(new Path("/hdfsapi/test"));
  }

  //查看hdfs内容
  @Test
  public void text()throws Exception{
  FSDataInputStream in =fileSystem.open(new Path("/cdh_version.properties"));
  IOUtils.copyBytes(in,System.out,1024);
  }

  //创建文件
  @Test
  public void create()throws Exception{
  //FSDataOutputStream out =fileSystem.create(new Path("/hdfsapi/test/a.txt"));
  FSDataOutputStream out =fileSystem.create(new Path("/hdfsapi/test/b.txt"));
  out.writeUTF(" hello PK:replication 1");
  out.flush();
  out.close();
  //hadoop fs -cat /hdfsapi/test/a.txt
  }

  //副本测试
  @Test
  public void testReplication(){
  //System.out.println(configuration.get(“dfs.replication”));
  //configuration.get(“dfs.replication”);
  System.out.println(configuration.get(“dfs.replication”));
  }

  @After
  public void tearDown(){
  configuration=null;
  fileSystem=null;
  System.out.println(“tearDown_”);
  }

  //public static final String HDFS_PATH = “hdfs://hadoop000:8020”;
  // public static void main(String[] args) throws Exception{
  //
  // //hadoop2017:8020
  // //虚拟机IP192.168.1.127
  // Configuration configuration=new Configuration();
  // //FileSystem fileSystem=FileSystem.get(new URI(“HDFS_PATH”),configuration,“hadoop”);
  // FileSystem fileSystem=FileSystem.get(new URI(“hdfs://192.168.1.127:8020”),configuration,“hadoop”);

//
//
//
// Path path=new Path("/hdfsapi/test");
// boolean result=fileSystem.mkdirs(path);
//
// System.out.println(result);
// }
}