hadoop2.2编程：序列化

测试序列化后的长度

提示：需要用到的类，以及继承关系如下：

1.java.lang.Object 

  |__ java.io.OutputStream 

           |__ java.io.ByteArrayOutputStream

                  //description

                     public class ByteArrayOutputStream

                     extends OutputStream

                   //method

                     byte[] toByteArray()   //Creates a newly allocated byte array. 

2.java.lang.Object 

      |__ java.io.OutputStream 

               |__ java.io.FilterOutputStream 

                        |__ java.io.DataOutputStream

                             //description

                                public class DataOutputStream

                                extends FilterOutputStream

                                implements DataOutput

3. java.lang.Object 

      |__ java.io.OutputStream 

           // description

               public abstract class OutputStream

               extends Object

                implements Closeable, Flushable

            //mdthods

               void close() 

               void flush() 

               void write(byte[] b) 

               void write(byte[] b, int off, int len) 

               abstract void write(int b) 

4.org.apache.hadoop.io 

Interface Writable

 //description   

    public interface Writable

 //methods

   void readFields(DataInput in)  

   void write(DataOutput out)  

5. java.lang.Object

       |__ org.apache.hadoop.io.IntWritable

              //description

                 public class IntWritableextends Object

                 implements   WritableComparable

               // methods

                   int get() 

                   void readFields(DataInput in)  

                   void set(int value)  

                   void write(DataOutput out) 

6. java.lang.Object

      |__ org.apache.hadoop.util.StringUtils

            //description

              public class StringUtils

              extends Object    

            //method

               static String byteToHexString(byte[] bytes)  

               static String capitalize(String s)  

               static String[] split(String str) 

               static Path[] stringToPath(String[] str) 

               static URI[] stringToURI(String[] str) 

               static String uriToString(URI[] uris) 

代码：

import java.io.DataOutputStream;

import java.io.ByteArrayOutputStream;

import java.lang.Byte;



import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.IOUtils;

import org.apache.hadoop.util.StringUtils;

public class TestWritable extends IntWritable {



  public static byte[] serialize(IntWritable writable) throws Exception {

    ByteArrayOutputStream out = new ByteArrayOutputStream();

    DataOutputStream dataOut = new DataOutputStream(out);

    writable.write(dataOut);

    dataOut.close();

    return out.toByteArray();

  }



  public static void main(String[] args) throws Exception {

    IntWritable i = new IntWritable();

    i.set(8);

    System.out.println(i.get());

    byte[] bytes = serialize(i);

    System.out.println(bytes.toString().length());

    System.out.println(StringUtils.byteToHexString(bytes));

  }

}