SequenceFile实例操作详解大数据

 1 package Hdfs; 
 2  
 3 import java.io.IOException; 
 4 import java.net.URI; 
 5  
 6 import org.apache.hadoop.conf.Configuration; 
 7 import org.apache.hadoop.fs.FileSystem; 
 8 import org.apache.hadoop.fs.Path; 
 9 import org.apache.hadoop.io.IOUtils; 
10 import org.apache.hadoop.io.IntWritable; 
11 import org.apache.hadoop.io.SequenceFile; 
12 import org.apache.hadoop.io.Text; 
13  
14 public class SequenceFileWriter { 
15     private static final String[] text={ 
16         "床前明月光", 
17         "疑似地上霜", 
18         "举头望明月", 
19         "低头思故乡" 
20     }; 
21     public static void main(String[] args) { 
22         String uri="hdfs://neusoft-master:9000/user/root/test/demo1"; 
23         Configuration conf=new Configuration(); 
24         SequenceFile.Writer writer=null; 
25          
26         try { 
27             FileSystem fs= FileSystem.get(URI.create(uri), conf); 
28             Path path = new Path(uri); 
29             IntWritable key = new IntWritable(); 
30             Text value = new Text(); 
31             writer = SequenceFile.createWriter(fs, conf, path, key.getClass(), value.getClass()); 
32             for (int i = 0; i < 100; i++) { 
33                 key.set(100-i); 
34                 value.set(text[i%text.length]); 
35                 writer.append(key, value); 
36             } 
37         } catch (IOException e) { 
38             e.printStackTrace(); 
39         }finally{ 
40             IOUtils.closeStream(writer); 
41         } 
42     } 
43 }

 1 package Hdfs; 
 2  
 3 import java.io.IOException; 
 4 import java.net.URI; 
 5  
 6 import org.apache.hadoop.conf.Configuration; 
 7 import org.apache.hadoop.fs.FileSystem; 
 8 import org.apache.hadoop.fs.Path; 
 9 import org.apache.hadoop.io.IOUtils; 
10 import org.apache.hadoop.io.SequenceFile; 
11 import org.apache.hadoop.io.Writable; 
12 import org.apache.hadoop.util.ReflectionUtils; 
13  
14 public class SequenceFileReader { 
15      
16     public static void main(String[] args) { 
17         String uri="hdfs://neusoft-master:9000/user/root/test/demo1"; 
18         Configuration conf = new Configuration(); 
19         SequenceFile.Reader reader =null; 
20         try { 
21             FileSystem fs = FileSystem.get(URI.create(uri),conf); 
22             Path path = new Path(uri); 
23             reader=new SequenceFile.Reader(fs, path,conf); 
24             Writable key = (Writable)ReflectionUtils.newInstance(reader.getKeyClass(), conf); 
25             Writable value =(Writable)ReflectionUtils.newInstance(reader.getValueClass(), conf);  
26             long position = reader.getPosition(); 
27             while (reader.next(key,value)) { 
28                 System.out.printf("[%s]/t%s/n",key,value); 
29                 position=reader.getPosition(); 
30             } 
31         } catch (IOException e) { 
32             e.printStackTrace(); 
33         }finally{ 
34             IOUtils.closeStream(reader); 
35         } 
36          
37     } 
38 }