Java 序列化与反序列化（Serialization）

1、什么是？为何须要？

序列化（Serialization）是将对象的状态信息转化为能够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；传输须要；一些应用场景中须要将对象持久化下来，以便在须要的时候进行读取。

2、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，若是没有重写 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，用来控制须要序列化哪些字段

3、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()); } }

4、一些细节

1.序列化ID

serialVersionUID  若是两个类的ID不一样，则不能互相序列与反序列（可应用与版本控制，不一样版本的类相互兼容或者不兼容）

2.安全性

因为其标准化致使其有泄露的风险（二进制明文，可采用加密的方法）