对象序列化

一、什么是对象序列化？

对象序列化：就是将一个对象转换为二进制数据流。

如果一个类对象要想实现对象序列化，怎对象所在的类必须实现Serializable(序列化)接口。

在此接口中没有任何的方法，此接口只是作为一个标识，表示本类的对象具备了序列化的能力而已。

如果要想完成对象的序列化，则还要依靠ObjectOutputStream类和 ObjectInputStream类，前者属于序列化操作，后者属于反序列化操作。

package com.demo.io;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;

public class SerializableDemo {
	public static void main(String[] args) throws IOException {
		OutputStream outputStream= new FileOutputStream("g:"+File.separator+"SerializableDemo.txt");
		ObjectOutputStream oop = new ObjectOutputStream(outputStream);
		Person person = new Person(11, "张三");
		oop.writeObject(person);
		outputStream.close();
		oop.close();
	}

}
class Person implements Serializable{
	private int age;
	private String name;
	public Person(int age, String name) {
		this.age = age;
		this.name = name;
	}
	public String toString(){
		return "姓名："+name +"年龄："+age;
	}
	
}

//结果： sr com.demo.io.Person窹{NDp I ageL namet Ljava/lang/String;xp   t 寮犱笁

对象被序列化之后，就可以通过ObjectInputStream进行反序列化的操作。

package com.demo.io;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;

public class UNSerializableDemo {
	public static void main(String[] args) throws IOException, ClassNotFoundException {
		InputStream inputStream= new FileInputStream("g:"+File.separator+"SerializableDemo.txt");
		ObjectInputStream ois = new ObjectInputStream(inputStream);
		Object object=ois.readObject();
		Person person = (Person)object;
		System.out.println(person);
	}

}

以上的操作实际上是将整个对象进行序列化的操作，如果现在假设类中的某个属性不希望被序列化的话，则要使用transient（短暂的）关键字声明。

package com.demo.io;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;

public class SerializableDemo {
	public static void main(String[] args) throws IOException {
		OutputStream outputStream= new FileOutputStream("g:"+File.separator+"SerializableDemo.txt");
		ObjectOutputStream oop = new ObjectOutputStream(outputStream);
		Person person = new Person(11, "张三");
		oop.writeObject(person);
		outputStream.close();
		oop.close();
	}

}
class Person implements Serializable{
	private transient int age;
	private transient String name;
	public Person(int age, String name) {
		this.age = age;
		this.name = name;
	}
	public String toString(){
		return "姓名："+name +"年龄："+age;
	}
	
}

//结果 sr com.demo.io.Person`?e巌覧  xp

package com.demo.io;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;

public class UNSerializableDemo {
	public static void main(String[] args) throws IOException, ClassNotFoundException {
		InputStream inputStream= new FileInputStream("g:"+File.separator+"SerializableDemo.txt");
		ObjectInputStream ois = new ObjectInputStream(inputStream);
		Object object=ois.readObject();
		Person person = (Person)object;
		System.out.println(person);
	}

}

//结果：姓名：null年龄：0

如何同时对多个对象一起进行序列化操作呢？

Object类可以接收任意的引用数据类型，包括数组。

package com.demo.io;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;

public class SerializableDemo {
	public static void main(String[] args) throws IOException {
		OutputStream outputStream= new FileOutputStream("g:"+File.separator+"SerializableDemo.txt");
		ObjectOutputStream oop = new ObjectOutputStream(outputStream);
		Person persons[] = {new Person(11, "张三"),new Person(12, "李四"),new Person(13, "王五")};
		oop.writeObject(persons);
		outputStream.close();
		oop.close();
	}

}
class Person implements Serializable{
	private  int age;
	private  String name;
	public Person(int age, String name) {
		this.age = age;
		this.name = name;
	}
	public String toString(){
		return "姓名："+name +"年龄："+age;
	}
	
}

//结果 ur [Lcom.demo.io.Person;粸)oz?;  xp   sr com.demo.io.Person窹{NDp I ageL namet Ljava/lang/String;xp   t 寮犱笁sq ~    t 鏉庡洓sq ~    
//t 鐜嬩簲

package com.demo.io;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;

public class UNSerializableDemo {
	public static void main(String[] args) throws IOException, ClassNotFoundException {
		InputStream inputStream= new FileInputStream("g:"+File.separator+"SerializableDemo.txt");
		ObjectInputStream ois = new ObjectInputStream(inputStream);
		Object object=ois.readObject();
		Person persons[] = (Person[])object;
		for(Person person:persons){
			System.out.println(person);
		}
		
	}

}

//结果：姓名：张三年龄：11
//姓名：李四年龄：12
//姓名：王五年龄：13

如果对一组对象进行序列化操作则必须使用数组概念