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Java 序列化与反序列化（Serialization）

2019-03-06 07:16:02来源：博客园阅读 ()

一、什么是？为什么需要？

序列化（Serialization）是将对象的状态信息转化为可以存储或者传输的形式的过程，反序列化则为其逆过程。

内存的易失性；传输需要；一些应用场景中需要将对象持久化下来，以便在需要的时候进行读取。

二、JDK提供的API

java.io.ObjectOutputStream类的 writeObject(Object obj)方法

java.io.ObjectInputStream类的readObject()方法

对于Serializable，如果没有重写 writeObject和readObject，则调用默认的方法

Externalizable继承了Serializable，多了2个方法：writeExternal和readExternal，用来控制需要序列化哪些字段

三、实现方法

假定一个Person类，实现了Serializable或Externalizable接口

import java.io.Serializable;

/**
 * @Author: pf_xu
 * @Date: 2019/3/5 12:37
 * @Version 1.0
 */
public class Person implements Serializable {

    private int age;
    private String name;

    public Person(int age, String name) {
        this.age = age;
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public String getName() {
        return name;
    }

}

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

/**
 * @Author: pf_xu
 * @Date: 2019/3/5 13:01
 * @Version 1.0
 */
public class SpecialPerson implements Externalizable {

    private int age;
    private String name;

    public SpecialPerson(){}

    public SpecialPerson(int age, String name) {
        this.age = age;
        this.name = name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public String getName() {
        return name;
    }

    @Override
    public void writeExternal(ObjectOutput out) throws IOException {
        out.writeObject(age);
        out.writeObject(name);
    }

    @Override
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
        this.age = (Integer) in.readObject();
        this.name = (String)in.readObject();
    }
}

import java.io.*;

/**
 * @Author: pf_xu
 * @Date: 2019/3/5 12:40
 * @Version 1.0
 */
public class SerializableDemo {
    public static void main(String[] args) throws IOException, ClassNotFoundException {

        Person person = new Person(10,"Simon");
        ObjectOutputStream oos1 = new ObjectOutputStream(new FileOutputStream("object1.out"));
        oos1.writeObject(person);
        ObjectInputStream ois1= new ObjectInputStream(new FileInputStream("object1.out"));
        Person re_person = (Person) ois1.readObject();
        System.out.println(re_person.getName()+"---"+re_person.getAge());

        SpecialPerson specialPerson = new SpecialPerson(30,"Daniel");
        ObjectOutputStream oos2 = new ObjectOutputStream(new FileOutputStream("object2.out"));
        oos2.writeObject(specialPerson);
        ObjectInputStream ois2= new ObjectInputStream(new FileInputStream("object2.out"));
        SpecialPerson re_specialPerson = (SpecialPerson)ois2.readObject();
        System.out.println(re_specialPerson.getName()+"---"+re_specialPerson.getAge());

    }
}