在hadoop框架来实现自己的类定义可以被序列化。

package com.rpc.nefu;import java.io.DataInput;import java.io.DataOutput;import java.io.IOException;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.io.WritableComparable;//自己定义的序列化方法，仅仅须要实现WritableComparable接口,重写一些方法就可以 主要就是 readFields() write() compareTo()public class personWritable implements WritableComparable
     
      {	private Text name;	private IntWritable age;	private Text sex;	public personWritable(){		set("name",-1,"female");	}	public personWritable(String _name,int _age,String _sex){		set(_name,_age,_sex);	}	public void set(String name,int age,String sex){		this.name = new Text(name);		this.age = new IntWritable(age);		this.sex = new Text(sex);	}	//反序列化过程，将datainput的内容还原为hadoop对象	@Override	public void readFields(DataInput in) throws IOException {		// TODO Auto-generated method stub		name.readFields(in);		age.readFields(in);		sex.readFields(in);	}	//序列化过程	@Override	public void write(DataOutput out) throws IOException {		// TODO Auto-generated method stub		name.write(out);		age.write(out);		sex.write(out);	}	@Override	public int compareTo(personWritable other) {		// TODO Auto-generated method stub		int cmp1 = name.compareTo(other.name);		if(cmp1!=0){			return cmp1;		}		int cmp2 = age.compareTo(other.age);		if(cmp2!=0){			return cmp2;		}		int cmp3 = sex.compareTo(other.sex);		return cmp3;	}	//推断是否相等	public boolean equals(Object o){		if(o instanceof personWritable){			personWritable pw = (personWritable) o;			return name.equals(pw.name)&&age.equals(pw.age)&&sex.equals(pw.sex);		}		return false;	}	//哈希值	public int hashCode(){		return name.hashCode()*3+age.hashCode()*5+sex.hashCode()*7;	}	public String toString(){		StringBuffer sb = new StringBuffer();		sb.append("--");		sb.append("姓名:"+name+"_");		sb.append("年龄:"+age+"_");		sb.append("性别:"+sex+"_");		sb.append("--");		return sb.toString();		}}
     

package com.rpc.nefu;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.IOException;//import org.apache.hadoop.io.Writable;//将序列化的对象的内容返回到一个字节数组中去 记录序列的过程public class hadoopSerializable {	public static byte[] serialize(personWritable writable) throws IOException{		//创建一个字节数组		ByteArrayOutputStream out = new ByteArrayOutputStream();		//创建一个DataOutputStream,将字节数组传递进去，保存输出的序列化后的内容        DataOutputStream dataout =  new DataOutputStream(out);         //让參数的Hadoop对象序列化到字节流中         writable.write(dataout);         dataout.close();         //返回序列化后的字节流         return out.toByteArray(); 	}			   /**		    *这种方法用于反序列化一个字节数组成Hadoop Writable对象 		    *@param writable 反序列化后的Writable对象存放在这个參数中 		    *@param bytes 被反序列化的字节数组 相应于上面序列化的bytes		    **/public static void deserialize(personWritable writable,byte[] bytes) throws Exception{                 ByteArrayInputStream in = new ByteArrayInputStream(bytes);         //创建一个DataInputStream         DataInputStream datain = new DataInputStream(in);         //让Hadoop框架反序列化这个字节数组，还原后的Writable对象存放到第一个參数中         writable.readFields(datain);                 datain.close();     } }

package com.rpc.nefu;import org.apache.hadoop.util.StringUtils;public class serializeTest {	public static void main(String [] args) throws Exception{                 /*把我们自己定义的Hadoop可序列化对象进行序列化 */        System.out.println("Hadoop--对象序列化");         personWritable pw = new personWritable("XD",23,"Male");         String imformation= "自己定义可序列化Hadoop类型为： "+pw.getClass().getName()+"\n";         String primaryPersonWritableInfo = "序列化前对象为：  "+pw.toString()+"\n";         //開始序列化过程         byte[] serializedValue =hadoopSerializable.serialize(pw);         String lengthInfo= "序列化后的字节数组长度为： "+serializedValue.length+"\n";         String serializeValueInfo= "序列化后的值为: " +StringUtils.byteToHexString(serializedValue)+"\n";          System.out.println(imformation+primaryPersonWritableInfo+lengthInfo+serializeValueInfo+"\n");                  System.out.println();         //把我们序列化之后的字节数组反序列化为原始Hadoop对象         System.out.println("反序列化--Hadoop");         personWritable reversePersonWritable = new personWritable();         /*StringUtils.byteToHexString 相似将自己数组转化为字符串*/        String originalByteArrayInfo="被反序列化的字节数组内容为： "+StringUtils.byteToHexString(serializedValue)+"\n";        //開始反序列化过程         hadoopSerializable.deserialize(reversePersonWritable, serializedValue);         String restoredValueInfo = "反序列化之后的Writable对象为: "+reversePersonWritable.toString();         System.out.println(originalByteArrayInfo+restoredValueInfo+"\n");     } }

此过程eclipse在完成，有可能是一个差异。

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