序列化和反序列化以及创建对象的几种方式

2022-09-08 14:05:49

    如何将对象中的信息永久保存
          1.将来将对象信息存入数据库
          2.java 中提供的序列化方式来永久保存数据

序列化流的概述
           所谓的序列化:就是把对象通过流的方式存储到文件中.注意:此对象 要重写Serializable 接口才能被序列化

package org.westos.Demo;

import java.io.*;

public class Demo2 {
    public static void main(String[] args) throws IOException {

        ObjectOutputStream obji = new ObjectOutputStream(new FileOutputStream("Object1.txt"));
        Teacher teacher = new Teacher();
        teacher.setName("张三");
        teacher.setAge(20);

        obji.writeObject(teacher);
        
    }
}


package org.westos.Demo;

import java.io.Serializable;

public class Teacher implements Serializable {
    private  String name;

    public Teacher() {
    }

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

    private  int age;

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "Teacher{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

注:如果没有实现Serializable接口,会出现NotSerializableException
       1)要求对象中的所有属性也都是可以序列化
       2)如果某个属性不想序列化,可以在属性上加`transient`关键字

反序列化:

              把字节内容读取进来,还原为java对象
             ObjectInputStream用来读取字节内容,还原(反序列化)为java对象

package org.westos.Demo;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.ObjectInputStream;

public class Demo4 {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        ObjectInputStream Obji = new ObjectInputStream(new FileInputStream("Object1.txt"));
        Teacher t =(Teacher) Obji.readObject();
        System.out.println(t.getName()+t.getAge());
    }
}

                   除了可以写入和读取对象以外,还可以写入和读取基本类型(int,long,boolean...) ,读取和写入的顺序要保持一致
                   如果不一致,出现EOFException
                   如果没有更多内容,也会出现EOFException
                   建议在写入时最后一个对象使用null,这样读取时就可以根据null来判断是否读取完毕

                   序列化和反序列化其实也是java中的一种数据传输的机制


创建对象的几种方式:

  1)new

  2)克隆:clone()

  3)反序列化

clone()举例

package org.westos.Demo;

public class Demo5 {
    public static void main(String[] args) throws CloneNotSupportedException {
        Teacher teacher1 = new Teacher();
        teacher1.setName("李四");
        teacher1.setAge(10);

        System.out.println(teacher1.getName()+"----"+teacher1.getAge());

        Teacher teacher2 = (Teacher)teacher1.clone();

        System.out.println(teacher2.getName()+"---"+teacher2.getAge());
        System.out.println(teacher1==teacher2);

    }
}


package org.westos.Demo;

import java.io.Serializable;

public class Teacher implements Serializable,Cloneable {
    private  String name;

    public Teacher() {
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

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

    private  int age;

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "Teacher{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

注:  克隆对应的设计模式:原型(prototype)模式 ,不走构造方法,根据一个已有对象创建新的对象。使用Cloneable接口和clone克隆的对象,仅仅是`浅拷贝`,如果属性为引用类型,复制的仅是地址。没有为这个属性创建新的对象`深拷贝` 利用序列化和反序列化生成新的对象,也会为属性创建新的对象

深拷贝举例

package org.westos.Demo;

import java.io.*;

public class Demo2 {
    public static void main(String[] args) throws IOException, ClassNotFoundException {

        ObjectOutputStream objo = new ObjectOutputStream(new FileOutputStream("Object1.txt"));
        Teacher teacher1 = new Teacher();
        teacher1.setName("张三");
        teacher1.setAge(20);


        objo.writeObject(teacher1);

        ObjectInputStream obji = new ObjectInputStream(new FileInputStream("Object1.txt"));
        Teacher teacher2 = (Teacher) obji.readObject();

        System.out.println(teacher2.getName()+"==="+teacher2.getAge());
        System.out.println(teacher2 == teacher1);

    }
}


ackage org.westos.Demo;

import java.io.Serializable;

public class Teacher implements Serializable,Cloneable {
    private  String name;

    public Teacher() {
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

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

    private  int age;

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "Teacher{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}
  • 作者:路还长@
  • 原文链接:https://blog.csdn.net/qq_41942241/article/details/81606226
    更新时间:2022-09-08 14:05:49