自定义类可序列化

时间：2021-10-08 19:22:20

在hadoop框架中实现自定义类可以被序列化。

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;

//自定义的序列化方法，只需要实现WritableComparable接口,重写一些方法即可 主要就是 readFields() write() compareTo()
public class personWritable implements WritableComparable<personWritable>{
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;
}
//判断是否相等
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); 
        //让参数的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(); 
}

   /**
    *这个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对象存放在这个参数中 
    *@param bytes 被反序列化的字节数组 对应于上面序列化的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对象存放到第一个参数中 
        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"; 
        //开始序列化过程 
        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 类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";
        //开始反序列化过程 
        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"); 
    } 
}

此过程在eclipse上完成，可能会存在出入。

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