Java基础-对象反序列化

对象反序列化：

• 使用到的流是对象字节输入流：ObjectInputStream
• 作用：以内存为基准，把存储到磁盘文件中去的对象数据恢复成内存中的对象，称为对象反序列化

package per.mjn.serializable;

import java.io.Serializable;

/**
 * 对象要序列化，必须实现Serializable序列化接口
 */
public class Student implements Serializable {

    private String name;
    private String loginName;
    // transient修饰的成员变量不参与序列化
    private transient String password;
    private int age;

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

    public Student() {
    }

    public Student(String name, String loginName, String password, int age) {
        this.name = name;
        this.loginName = loginName;
        this.password = password;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public String getLoginName() {
        return loginName;
    }

    public void setLoginName(String loginName) {
        this.loginName = loginName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getAge() {
        return age;
    }

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

package per.mjn.serializable;

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

/**
 * 对象反序列化，使用对象字节输入流把文件中的对象数据恢复成内存中的Java对象
 */
public class ObjectInputStreamDemo2 {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        // 1. 创建对象字节输入流管道包装低级的字节输入流管道
        ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream("d:/obj.txt"));

        // 2. 调用对象字节输入流的反序列化方法
        Student student = (Student) inputStream.readObject();

        System.out.println(student);
    }
}

下面引入序列化版本号，如果序列化对象发生改动（序列号发生改变），此时直接反序列化会报错。

 解决方案为，重新序列化一遍，然后再反序列化。

package per.mjn.serializable;

import java.io.Serializable;

/**
 * 对象要序列化，必须实现Serializable序列化接口
 */
public class Student implements Serializable {

    // 声明序列化的版本号
    // 序列化的版本号与反序列化的版本号必须一致才不会出错!
    private static final long serialVersionUID = 2;
    private String name;
    private String loginName;
    // transient修饰的成员变量不参与序列化
    private transient String password;
    private int age;

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

    public Student() {
    }

    public Student(String name, String loginName, String password, int age) {
        this.name = name;
        this.loginName = loginName;
        this.password = password;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public String getLoginName() {
        return loginName;
    }

    public void setLoginName(String loginName) {
        this.loginName = loginName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getAge() {
        return age;
    }

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

package per.mjn.serializable;

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

/**
 * 对象序列化，使用ObjectOutputStream将内存中的对象存入磁盘文件中
 * transient修饰的成员变量不参与序列化
 */
public class ObjectOutputStreamDemo1 {
    public static void main(String[] args) throws IOException {
        // 1. 创建学生对象
        Student s = new Student("mjn", "mjn", "1111", 22);

        // 2. 对象序列化，使用对象字节输出流包装字节输出流管道
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("d:/obj.txt"));

        // 3. 直接调用序列化方法
        objectOutputStream.writeObject(s);

        // 4. 释放资源
        objectOutputStream.close();
        System.out.println("序列化完成");
    }
}

package per.mjn.serializable;

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

/**
 * 对象反序列化，使用对象字节输入流把文件中的对象数据恢复成内存中的Java对象
 */
public class ObjectInputStreamDemo2 {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        // 1. 创建对象字节输入流管道包装低级的字节输入流管道
        ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream("d:/obj.txt"));

        // 2. 调用对象字节输入流的反序列化方法
        Student student = (Student) inputStream.readObject();

        System.out.println(student);
    }
}