Java之对象序列化与反序列化

1.将对象转换为字节流保存起来，并在以后还原这个对象，这种机制叫做对象序列化。

2.将一个对象保存到永久存储设备上称为持久化。

3.一个类若想被序列化，则需要实现java,io.Serializable接口，该接口中没有定义任一方法，是一个标志性接口（Mark Interface），当一个类实现了该接口，就说明该类是可以序列化的。

4.在序列化时，static变量是无法序列化的；如果A包含了对B的引用，那么在序列化A的时候也会将B一并地序列化；如果此时A可以序列化，B无法序列化，那么在序列化A的时候就会发生异常，这时就需要将对B的引用设为transient，该关键字表示变量不会被序列化。

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
/**
 * 对象序列化与反序列化
 * @author c
 */
public class SerializableTest1
{
	public static void main(String[] args) throws Exception
	{
		Person p1 = new Person(1, "张三", 21);
		Person p2 = new Person(2, "李四", 22);
		Person p3 = new Person(3, "王五", 20);
		
		FileOutputStream fos = new FileOutputStream("E:\\eclipse4.2\\JavaIo\\doc\\Person.txt");
		ObjectOutputStream oos = new ObjectOutputStream(fos);
		oos.writeObject(p1);
		oos.writeObject(p2);
		oos.writeObject(p3);
		oos.close();
		
		System.out.println("-----------------");
		FileInputStream fis = new FileInputStream("E:\\eclipse4.2\\JavaIo\\doc\\Person.txt");
		ObjectInputStream ois = new ObjectInputStream(fis);
		Person p = null;
		for (int i = 0; i < 3; i++)
		{
			p = (Person)ois.readObject();
			System.out.println("id = " + p.id + ",name = " + p.name + ",int = " + p.age);
		}
		ois.close();
	}
}

class Person implements Serializable {
	/*
	 * 加Static或transient关键字则不能被存储
	 */
	int id;
	String name;
	int age;
	public Person(int id, String name, int age) {
		this.id = id;
		this.name = name;
		this.age = age;
	}
}

5.利用对象的序列化和反序列化，可以实现对对象的深克隆（当克隆的对象只有基本类型,不含引用类型时,可以用浅克隆实现，当克隆的对象含有引用类型时,必须使用深克隆实现）。

/*
 * 对象的浅克隆

 *1.实现Cloneable接口

 *2.重写clone()方法

 *3.在clone()方法中调用super.clone() 方法
 */
public class ShallowClone {
	public static void main(String[] args) {
		Student s1 = new Student();
		s1.setId(100);
		s1.setName("鸣人");
		System.out.println("克隆前的id:" + s1.getId());
		System.out.println("克隆前的name:" + s1.getName());
		
		try {
			Student s2 = (Student) s1.clone();
			System.out.println("克隆后的id:" + s2.getId());
			System.out.println("克隆后的name:" + s2.getName());
		} catch (CloneNotSupportedException e) {
			e.printStackTrace();
		}
	}
}
class Student implements Cloneable {
	private int id;
	private String name;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@Override
	public Object clone() throws CloneNotSupportedException {
		Student s = (Student) super.clone();
		return s;
	}
}

package com.deepclone;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

/*
 * 利用对象序列化实现对象的深克隆

 *1.实现Serializable接口

 *2.利用ObjectOutputStream的writeObject方法将要克隆的对象序列化

 *3.利用ObjectInputStream的readObject方法将克隆得到的对象反序列化
 */
public class DeepCopy {
	public static void main(String[] args) {
		Father father = new Father();
		father.setAge(20);
		father.setName("四代火影");
		Son son = new Son();
		son.setAge(18);
		son.setName("鸣人");
		son.setFather(father);
		System.out.println("克隆前son的age:" + son.getAge());
		System.out.println("克隆前son的name:" + son.getName());
		System.out.println("克隆前fathor的age:" + son.getFather().getAge());
		System.out.println("克隆前fathor的name:" + son.getFather().getName());
		System.out.println("---------------------------");
		Son son2 = (Son)son.copyObject();
		System.out.println("克隆前son的age:" + son2.getAge());
		System.out.println("克隆前son的name:" + son2.getName());
		System.out.println("克隆前fathor的age:" + son2.getFather().getAge());
		System.out.println("克隆前fathor的name:" + son2.getFather().getName());
		
		System.out.println("---------------------------");
		son2.getFather().setAge(21);
		son2.getFather().setName("波分水门");
		System.out.println("克隆前fathor的age:" + son.getFather().getAge());
		System.out.println("克隆前fathor的name:" + son.getFather().getName());
		System.out.println("克隆前fathor的age:" + son2.getFather().getAge());
		System.out.println("克隆前fathor的name:" + son2.getFather().getName());
	}
}
class Father implements Serializable {
	private static final long serialVersionUID = 1L;
	private String name;
	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;
	}
}
class Son implements Serializable {
	private static final long serialVersionUID = 1L;
	private String name;
	private int age;
	private Father father;
	public Father getFather() {
		return father;
	}
	public void setFather(Father father) {
		this.father = father;
	}
	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;
	}
	/*
	 * 实现对象的序列化与反序列化
	 */
	public Object copyObject() {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		try {
			ObjectOutputStream oos = new ObjectOutputStream(baos);
			oos.writeObject(this);	//对象序列化
		} catch (IOException e) {
			e.printStackTrace();
		}
		ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
		Object object = null;
		try {
			ObjectInputStream ois = new ObjectInputStream(bais);
			object = ois.readObject();	//对象反序列化
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
		return object;
	}
}