Java 实体类中的 serialVersionUID 作用解释

实验一： 实体 User 中没有  serialVersionUID 字段的时候

@Data
public class User implements Serializable {3 

    private Integer id;

    private String name;

}

　　test 代码：

    @Test
    void testSerilze() throws Exception {
　　　　　　　// 序列化 user 对象保存到文件中
        User user = new User();
        user.setName("wahahha");
        FileOutputStream outputStream = new FileOutputStream("user");
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
        objectOutputStream.writeObject(user);
        objectOutputStream.close();

    }

    @Test
    void testRead() throws Exception{
　　　　　　//从文件中反序列化 user 对象
        FileInputStream inputStream = new FileInputStream("user");
        ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
        User user = (User)objectInputStream.readObject();
        System.out.println(user);
    }

输入结果正常： User(id=null, name=wahahha, age=null)

public class User implements Serializable {

    private Integer id;

    private String name;
    // 添加字段 age  
    private Integer age;

}

执行 test: 

    @Test
    void testRead() throws Exception{
        FileInputStream inputStream = new FileInputStream("user");
        ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
        User user = (User)objectInputStream.readObject();
        System.out.println(user);
    }

抛出异常： 

java.io.InvalidClassException: com.ym.mybatisplus.pojo.User; local class incompatible: stream classdesc serialVersionUID = 1, local class serialVersionUID = -8191989038804560538

 

　　结果证明： 如果没有 serialVersionUID 字段， 那么实体类如果改变，那么再反序列化的时候，就会导致失败，抛出异常

 

实验二： 实体 User 中添加  serialVersionUID 字段

@Data
public class User implements Serializable {

    private static final long serialVersionUID=1L;

    private Integer id;

    private String name;

}

执行序列化：

    @Test
    void testSerilze() throws Exception {
        User user = new User();
        user.setName("wahahha");
        FileOutputStream outputStream = new FileOutputStream("user");
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
        objectOutputStream.writeObject(user);
        objectOutputStream.close();
    }

 

然后修改 User, 添加字段 age:

@Data
public class User implements Serializable {

    private static final long serialVersionUID=1L;

    private Integer id;

    private String name;

    private Integer age;

}

 

然后执行反序列化：

    @Test
    void testRead() throws Exception{
        FileInputStream inputStream = new FileInputStream("user");
        ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
        User user = (User)objectInputStream.readObject();
        System.out.println(user);
    }

正常输出反序列化结果：　

User(id=null, name=wahahha, age=null)

 

结果证明： serialVersionUID 字段可以用来保证对象的一致性，在序列化和反序列化的时候，可以保持兼容性，可以正确反序列化成功。