序列化和反序列化以及创建对象的几种方式

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 +
                '}';
    }
}