java - java Serializable接口没有功能,为什么会影响“writeObject”/“readObject”
问题描述
我检查了接口
Serializable
没有函数定义,但是当我定义
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。
但是在可序列化中,如果我定义自己的“writeObject”/“readObject”,编译器如何生成代码,它们在序列化时被调用?
我试图附加
@Override
在这两个函数之上的注释,编译器报告错误。
那么它是如何工作的,你能帮忙解释一下吗?
非常感谢!
解决方案
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();
}
}
}
工人.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 + "$";
}
}
推荐阅读
- ruby - 如何在mongodb中运行继承类的方法?
- javascript - 是否有一种简单快捷的方法可以从 javascript 对象中删除 x 键而不循环键?
- php - 如何在php中的url中获取'@'-selector之后的所有内容
- javascript - 永久保存对 ContentEditable 所做的更改?
- java - 为什么在使用 LocalDate 作为 POJO 的数据类型时,univocity 的 CsvParser 会抛出错误以及如何解决它?
- google-api - 如何构建一个使用谷歌日历 api 而无需验证的 web 应用程序?
- c# - 通用工作单元
- python - Python对象实例中的dict不包含类的方法
- python - 将熊猫数据框转换为 keras 的分类
- sublimetext3 - 在 Sublime Text 中折叠/展开母版时,在任何级别上保留子折叠