java序列化与反序列化

1.定义

• 序列化：将java对象转换为二进制字节流
• 反序列化：将二进制字节流转换为java对象

2.实现序列化的方式

• 实现Serializable接口（transient关键字修饰的字段不会被序列化和反序列化）

3.序列化和反序列化测试

package com.example.demo.srializable;

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

import java.io.Serializable;

@Getter
@Setter
@ToString
public class User implements Serializable {

    private static final long serialVersionUID = 1L;

    private transient String id;

    private String name;

    private String sex;

    private int age;


}

public static void main(String[] args) throws Exception {
        User user = new User();
        user.setId("1");
        user.setName("张三");
        user.setSex("男");
        user.setAge(20);
        System.out.println(user);

        ObjectOutputStream objectOutputStream = null;
        ObjectInputStream objectInputStream = null;
        try {
            objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("D://User")));
            objectOutputStream.writeObject(user);

            objectInputStream = new ObjectInputStream(new FileInputStream(new File("D://User")));
            User user2 = (User) objectInputStream.readObject();
            System.out.println(user2);
        } finally {
            objectOutputStream.close();
            objectInputStream.close();
        }
    }

打印结果：
可以看到，id字段被transient修饰的，所以反序列化后的值为null。

4.关于serialVersionUID

• serialVersionUID是用来反序列化时验证对象是否一致的

现在我们将User对象中的serialVersionUID改为2，然后直接反序列化之前的文件。

private static final long serialVersionUID = 2L;

public static void main(String[] args) throws Exception {
        
        ObjectInputStream objectInputStream = null;
        try {
            objectInputStream = new ObjectInputStream(new FileInputStream(new File("D://User")));
            User user2 = (User) objectInputStream.readObject();
            System.out.println(user2);
        } finally {
            objectInputStream.close();
        }
    }

Exception in thread "main" java.io.InvalidClassException: com.example.demo.srializable.User; local class incompatible: stream classdesc serialVersionUID = 1, local class serialVersionUID = 2
	at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:616)
	at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1829)
	at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1713)
	at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1986)
	at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1535)
	at java.io.ObjectInputStream.readObject(ObjectInputStream.java:422)
	at com.example.demo.srializable.Test.main(Test.java:16)

可以看到，反序列化时直接报错了，提示serialVersionUID不一致。

本文地址：https://blog.csdn.net/qq_34857603/article/details/107676687