概念

序列化

将对象转换为字节序列的过程叫做对象的序列化。

对象在jvm运行的时候是存在的，但是一旦jvm运行结束之后，对象也会随之消失，那么如果我们不想让这个对象消失，那么就可以将它以字节描述的形式保存下来，这个转换的过程就叫做序列化。

反序列化

将字节序列恢复为对象的过程叫做对象的反序列化。

假如我们想在运行的时候使用已经保存好的对象，那么这个从字节描述转换为对象的过程就叫做反序列化。

用途

对象的序列化操作的主要用途有两种：

将对象序列化后永久地保存到硬盘上，比如保存到数据库或是保存为文件；
将对象序列化后用于网络传输。

实现方式

接口

在Java中，要使一个类可以被序列化/反序列化，共有两种序列化接口可以选择：

Serializable接口；
Externalizable接口。

Serializable接口是一个空接口，它的作用是声明当前类可以被序列化和反序列化，序列化操作与反序列化操作使用的是默认规则。

/*
 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 */

package java.io;

public interface Serializable {
}

Externalizable接口继承自Serializable接口，包括了两个未实现的方法，用于自定义序列化操作时的规则和反序列化操作时的规则。

/*
 * Copyright (c) 1996, 2004, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 */

package java.io;

import java.io.ObjectOutput;
import java.io.ObjectInput;

public interface Externalizable extends java.io.Serializable {
    /**
     * The object implements the writeExternal method to save its contents
     * by calling the methods of DataOutput for its primitive values or
     * calling the writeObject method of ObjectOutput for objects, strings,
     * and arrays.
     *
     * @serialData Overriding methods should use this tag to describe
     *             the data layout of this Externalizable object.
     *             List the sequence of element types and, if possible,
     *             relate the element to a public/protected field and/or
     *             method of this Externalizable class.
     *
     * @param out the stream to write the object to
     * @exception IOException Includes any I/O exceptions that may occur
     */
    void writeExternal(ObjectOutput out) throws IOException;

    /**
     * The object implements the readExternal method to restore its
     * contents by calling the methods of DataInput for primitive
     * types and readObject for objects, strings and arrays.  The
     * readExternal method must read the values in the same sequence
     * and with the same types as were written by writeExternal.
     *
     * @param in the stream to read data from in order to restore the object
     * @exception IOException if I/O errors occur
     * @exception ClassNotFoundException If the class for an object being
     *              restored cannot be found.
     */
    void readExternal(ObjectInput in) throws IOException, ClassNotFoundException;
}

I/O流类型

序列化对象时我们使用的I/O流类型为ObjectOutputStream类。

反序列化对象操作时我们使用的I/O流类型为ObjectInputStream类。

例子

定义一个对象类Ving类：

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package com.vingyun;

import java.io.Serializable;

public class Ving implements Serializable {
    /**
     * serialVersionUID 序列化与反序列化过程中的类信息校验
     */
    private static final long serialVersionUID = 1925138888826980930L;
    private String nickName;
    private int age;

    public String getNickName() {
        return nickName;
    }
    public void setNickName(String nickName) {
        this.nickName = nickName;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
}

package com.vingyun;

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

public class SerializeTest {

    public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
        // TODO 自动生成的方法存根
        Ving vingSerialize = new Ving();
        vingSerialize.setNickName("MasterVing");
        vingSerialize.setAge(99);
        serializeVing(vingSerialize);

        Ving vingDeserialize = null;
        vingDeserialize = deserializeVing(vingDeserialize);
        System.out.println("NickName: " + vingDeserialize.getNickName() + "\nAge: " + vingDeserialize.getAge());

    }

    public static void serializeVing(Ving vingSerialize) throws FileNotFoundException, IOException {
        ObjectOutputStream obOStream = new ObjectOutputStream(new FileOutputStream("E:/vingInfo.txt"));
        obOStream.writeObject(vingSerialize);
        obOStream.close();
        System.out.println("序列化对象操作完成。\n");
    }

    public static Ving deserializeVing(Ving vingDeserialize) throws FileNotFoundException, IOException, ClassNotFoundException {
        ObjectInputStream obIStream = new ObjectInputStream(new FileInputStream("E:/vingInfo.txt"));
        vingDeserialize = (Ving) obIStream.readObject();
        obIStream.close();
        System.out.println("反序列化对象操作完成。\n");
        return vingDeserialize;
    }
}

这里写图片描述

【Java】序列化与反序列化

概念

序列化

反序列化

用途

实现方式

接口

I/O流类型

例子

相关属性

serialVersionUID

serialPersistentFields

相关关键字

transitent

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