自定义类可序列化

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@Overridepublic void readFields(DataInput in) throws IOException {// TODO Auto-generated method stubname.readFields(in);age.readFields(in);sex.readFields(in);}//序列化过程@Overridepublic void write(DataOutput out) throws IOException {// TODO Auto-generated method stubname.write(out);age.write(out);sex.write(out);}@Overridepublic int compareTo(personWritable other) {// TODO Auto-generated method stubint 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。