序列化 Serializable

1.Serializable

类通过实现 java.io.Serializable 接口以启用其序列化功能。未实现此接口的类将无法使其任何状态序列化或反序列化，并抛出异常；

异常代码：

java.io.NotSerializableException: cn.a2.serializable.Student
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1180)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
    at cn.a2.serializable.Test1.main(Test1.java:22)

package cn.a2.serializable;

import java.io.Serializable;

public class Student implements Serializable {

    private String id;
    private String name;
    private int age;
    private Gender gender;
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    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;
    }
    public Gender getGender() {
        return gender;
    }
    public void setGender(Gender gender) {
        this.gender = gender;
    }
    public Student(String id, String name, int age, Gender gender) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
    }
    public Student() {
        super();
    }
    
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", age=" + age
                + ", gender=" + gender + "]";
    }
    

}

enum Gender {
    男, 女;

}

把属性信息写入d:"+File.separator+"javatest"+File.separator+"e.txt文件里：

package cn.a2.serializable;

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

public class Test1 {
    public static void main(String[] args) throws FileNotFoundException, IOException {
        Student student = new Student("1001", "小明", 20, Gender.男);
        
        /*
         *取stu所有属性，通过特定的字符串（-）,把各个属性值连接起来 
         * 1001-小明-20-男
         */
        
        File file = new File("d:"+File.separator+"javatest"+File.separator+"e.txt");
        FileOutputStream fos = new FileOutputStream(file);
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        
        oos.writeObject(student);
        
        oos.close();
        fos.close();
        
        
    }

}

反序列化

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

public class Test2 {
    public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
        File file = new File("d:"+File.separator+"javatest"+File.separator+"e.txt");
        
        FileInputStream iStream = new FileInputStream(file);
        ObjectInputStream ois = new ObjectInputStream(iStream);
        
        Student student = (Student)ois.readObject();
        System.out.println(student.getId());
        System.out.println(student.getName());
        System.out.println(student.getAge());
        System.out.println(student.getGender());
        
        iStream.close();
        ois.close();
    }

}

此时可能会出现异常

注意：

当序列化完成后，后期推送升级程序中的类(Student), 此时再反序列化时会出现异常。

Exception in thread "main" java.io.InvalidClassException: cn.sxt05.serializable.Student; local class incompatible: stream classdesc serialVersionUID = -6288733824962181189, local class serialVersionUID = 1690603786167234505
    at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:687)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1876)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1745)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2033)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1567)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:427)

 主要原因是没有给Student类加序列化版本号, 添加了就可以解决企业版本推送更新发生版本异常问题;

添加方式有两种：

以下代码添加后版本号之后，就可以解决推送更新版本号的问题；

package cn.a2.serializable;

import java.io.Serializable;

public class Student implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = -4427440848479890883L;//给Student类加序列化版本号,可以解决企业版本推送更新发生版本异常问题。    
    
    private String id;
    private String name;
    private int age;
    private Gender gender;
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    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;
    }
    public Gender getGender() {
        return gender;
    }
    public void setGender(Gender gender) {
        this.gender = gender;
    }
    public Student(String id, String name, int age, Gender gender) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
    }
    public Student() {
        super();
    }
    
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", age=" + age
                + ", gender=" + gender + "]";
    }
    

}

enum Gender {
    男, 女;

}

 反序列化

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

public class Test2 {
    public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
        File file = new File("d:"+File.separator+"javatest"+File.separator+"e.txt");
        
        FileInputStream iStream = new FileInputStream(file);
        ObjectInputStream ois = new ObjectInputStream(iStream);
        
        Student student = (Student)ois.readObject();
        System.out.println(student.getId());
        System.out.println(student.getName());
        System.out.println(student.getAge());
        System.out.println(student.getGender());
        
        iStream.close();
        ois.close();
    }

}

 添加后版本号之后，就可以解决了更新版本号异常问题，所以以后企业开发过程中，一定要记得添加版本号。