java Serializable接口没有功能，为什么会影响“writeObject”/“readObject”

Question

我检查了界面

Serializable

没有函数定义，但当我定义时

private void readObject(ObjectOutputStream oos){
    System.out.println("readObject!!");
}
private void writeObject(ObjectOutputStream oos){
    System.out.println("writeObject!!");
}

类中的函数，它们在对象被序列化时被调用。

这对我来说很奇怪，如果接口定义了这两个函数，那么我应该重写它们以确保它们被调用。

但是在 Serializable 中，如果我定义自己的“writeObject”/“readObject”，编译器如何生成代码，它们会在序列化时被调用？

我尝试添加

@Override

在两个函数上加注解，编译器报错。

那么它是如何工作的，你能帮忙解释一下吗？

非常感谢！

Answer 1

java.io.Serializable 是一个函数式接口，这意味着它没有在其中定义任何方法。如果您真的想确保没有人会尝试修改您的覆盖方法，则会放置 @Override 注释。您在@Override 上遇到编译器错误的原因是 Serializable 中没有这样的方法，但是您可以在 ObjectInputStream 和 ObjectOutputStream （分别用作低级类 FileInputStream 和 FileOutputStream ）中找到它们。 如果你真的想对一个列表进行序列化，你可以这样做：

package Chaper8.IO;

import java.io.*;

import java.util.*;

public class Serialization_Deserialization {

public static void main(String [] args){

    /*
     *  try-catch with resources, JVM makes sure to close the resources after you've finished using it
     * much easier than using finally and getting an exception for each resource closed
     * 
     */
    try(FileOutputStream out = new FileOutputStream("C:\\Users\\Andrei\\Desktop\\Exemple\\worker.txt");
        ObjectOutputStream oos = new ObjectOutputStream(out);

        FileInputStream in = new FileInputStream("C:\\Users\\Andrei\\Desktop\\Exemple\\worker.txt");
        ObjectInputStream ois = new ObjectInputStream(in);){

        //instances of the Worker class
        Worker w1 = new Worker("Worker1", 123456 , 2000.5);
        Worker w2 = new Worker("Worker2", 765436, 1500.15);
        Worker w3 = new Worker("Worker3", 364582, 1700.45);
        Worker w4 = new Worker("Worker4", 878234, 2100.34);
        ArrayList<Worker> list = new ArrayList<>();

        //just adding the persons in the list
        list.add(w1);
        list.add(w2);
        list.add(w3);
        list.add(w4);


        System.out.println("Doing serialization");
        oos.writeObject(list);

        System.out.println("Doing deserialization");
        ois.readObject();

    }catch(IOException | ClassNotFoundException e){
            e.printStackTrace();
    }
}
} 

Worker.java

/*
 *  Worker class, basic type with variables, constructor, and toString() overridden
 *  Here I have implemented Serializable for the reason that I need to make sure that
 *  I will serialize the object within the class
 *
 *  Note that I used transient for id. transient is a special keyword which makes sure 
 * that id will not be serialized, used for security reasons.
 * 
 *  serialVersionUID is another variable which is used during deserialization 
 * to verify that the sender and receiver of a serialized object have loaded 
 * classes for that object that are compatible with respect to serialization. 
 *  Throws InvalidClassException if the object has a different serialVersionUID
 * than that of the corresponding sender's class.
 *  
 */

import java.io.*;
class Worker implements Serializable{

private static final long serialVersionUID = 1L;
private String name;
private transient int id;
private double wage;

public Worker(String name, int id, double wage){
    this.name = name;
    this.id = id;
    this.wage = wage;
}
public String toString(){
    return "Person with name " +
    name + " and with id " +
    id + " has a salary of " + wage + "$";
    }
}