序列化serialversionid作用

显示声明serialVersionUID可以避免对象不一致

实例1：有serialVersionUID

序列化与反序列实体类

public class Person2 implements Serializable{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    /**
     * 
     */
    public Long id;
    public String name;
    public final String userName;
    public String sex;
    public int age;
 
    public Person2(Long id, String name,String sex,int age){
        this.id = id;
        this.name = name;
        userName = "dddbbb";
        this.sex=sex;
        this.age=age;
    }
 
    public String toString() {
        return id.toString() + "--" + name.toString();
    }
}

序列化类：

public class SerialTest {
     public static void main(String[] args) {
            Person2 p = new Person2(1L, "陈俊生","male",22);
            System.out.println("person Seria:" + p);
            try {
                FileOutputStream fos = new FileOutputStream("Persion.txt");
                ObjectOutputStream oos = new ObjectOutputStream(fos);
                oos.writeObject(p);
                oos.flush();
                oos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

}

序列化执行完成之后，反序列化执行之前，如果更改了实体类Person后，在执行反序列化代码

public class DeserialTest {
    public static void main(String[] args) {
        Person2 p;
        try {
            FileInputStream fis = new FileInputStream("Persion.txt");
            ObjectInputStream ois = new ObjectInputStream(fis);
            p = (Person2) ois.readObject();
            ois.close();
            System.out.println(p.toString());
            System.out.println(p.userName);
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

结果没有异常

 

 

实例化2：无serialVersionUID

public class Person2 implements Serializable{
    /**
     * 
     *
    /**
     * 
     */
    public Long id;
    public String name;
    public final String userName;
    public String sex;
    public int age;
　　 pulic String school;/////序列化之后，反序列化之前新增字段
 
    public Person2(Long id, String name,String sex,int age){
        this.id = id;
        this.name = name;
        userName = "dddbbb";
        this.sex=sex;
        this.age=age;
    }
 
    public String toString() {
        return id.toString() + "--" + name.toString();
    }
}

序列化类：

public class SerialTest {
     public static void main(String[] args) {
            Person2 p = new Person2(1L, "陈俊生","male",22);
            System.out.println("person Seria:" + p);
            try {
                FileOutputStream fos = new FileOutputStream("Persion.txt");
                ObjectOutputStream oos = new ObjectOutputStream(fos);
                oos.writeObject(p);
                oos.flush();
                oos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

}

序列化执行完成之后，反序列化执行之前，如果更改了实体类Person后（本例中新增字段String school），在执行反序列化代码

public class DeserialTest {
    public static void main(String[] args) {
        Person2 p;
        try {
            FileInputStream fis = new FileInputStream("Persion.txt");
            ObjectInputStream ois = new ObjectInputStream(fis);
            p = (Person2) ois.readObject();
            ois.close();
            System.out.println(p.toString());
            System.out.println(p.userName);
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

此时反序列化代码抛出异常：

java.io.InvalidClassException: serial.Person2; local class incompatible: stream classdesc serialVersionUID = 5850213951562638361, local class serialVersionUID = -1986140618597495916
at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:699)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1885)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1751)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2042)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1573)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:431)
at serial.DeserialTest.main(DeserialTest.java:13)