序列化继承

我会带着你远行 2022-04-24 10:50 179阅读 0赞

相关注意事项  
a）序列化时，只对对象的状态进行保存，而不管对象的方法；  
b）当一个父类实现序列化，子类自动实现序列化，不需要显式实现Serializable接口；  
c）当一个对象的实例变量引用其他对象，序列化该对象时也把引用对象进行序列化；但是该对象也要实现序列化接口  
d）并非所有的对象都可以序列化，至于为什么不可以，有很多原因了,比如：  
1.安全方面的原因，比如一个对象拥有private，public等field，对于一个要传输的对象，比如写到文件，或者进行rmi传输等等，在序列化进行传输的过程中，这个对象的private等域是不受保护的。  
2. 资源分配方面的原因，比如socket，thread类，如果可以序列化，进行传输或者保存，也无法对他们进行重新的资源分配，而且，也是没有必要这样实现。  
3. 这些字段用transient修饰，就不被序列化

## 当一个父类实现序列化，子类自动实现序列化，不需要显式实现Serializable接口 ##

package com.study.demo.serialize;
    
    import lombok.Data;
    import lombok.ToString;
    
    import java.io.*;
    
    /**
     * Created by e-lipo on 2019/4/23.
     */
    public class SerializeTest {
        public static void main(String[] args) {
            PageForm pf = new PageForm();
            pf.setPageNum(1);
            pf.setPageSize(10);
            pf.setUserId("l23");
    
            try {
                FileOutputStream fos = new FileOutputStream("e:/serialize.txt");
                ObjectOutputStream oos = new ObjectOutputStream(fos);
                oos.writeObject(pf);
                oos.close();
                System.out.println("序列化: " + pf);//序列化: PageForm(super=BaseForm(userId=l23), pageNum=1, pageSize=10)
    
                FileInputStream fis = new FileInputStream("e:/serialize.txt");
                ObjectInputStream ois = new ObjectInputStream(fis);
                PageForm form = (PageForm)ois.readObject();
                System.out.println("反序列化: " + form);//反序列化: PageForm(super=BaseForm(userId=l23), pageNum=1, pageSize=10)
            } catch (Exception e) {
                e.printStackTrace();
            }
    
        }
    }
    
    //父类实现序列化接口，子类自动序列化
    @Data
    class BaseForm implements Serializable {
        private transient String  userId;
    }
    
    @Data
    @ToString(callSuper = true)
    class PageForm extends BaseForm {
        private Integer pageNum;
        private Integer pageSize;
    }

序列化结果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21pbmd3dWxpcG8_size_16_color_FFFFFF_t_70]

## 当一个对象的实例变量引用其他对象，序列化该对象时也把引用对象进行序列化 ##

但是该对象也要实现序列化接口

package com.study.demo.serialize;
    
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    import java.io.*;
    
    /**
     * Created by e-lipo on 2019/4/23.
     */
    public class SerializeTest2 {
        public static void main(String[] args) {
            User user = new User("lipo", new Address("浙江省", "hangzhou"));
    
            try {
                FileOutputStream fos = new FileOutputStream("e:/serialize.txt");
                ObjectOutputStream oos = new ObjectOutputStream(fos);
                oos.writeObject(user);
                oos.close();
                System.out.println("序列化: " + user);//序列化: User(username=lipo, address=Address(province=浙江省, city=hangzhou))
    
                FileInputStream fis = new FileInputStream("e:/serialize.txt");
                ObjectInputStream ois = new ObjectInputStream(fis);
                User form = (User)ois.readObject();
                ois.close();
                System.out.println("反序列化: " + form);//反序列化: User(username=lipo, address=Address(province=浙江省, city=hangzhou))
            } catch (Exception e) {
                e.printStackTrace();
            }
    
        }
    }
    
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    class User implements Serializable {
        private String username;
        private Address address;//类字段也必须实现序列化接口
    }
    
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    class Address implements Serializable {
        private String province;
        private String city;
    }

## 父类未实现Serializable，子类实现了，序列化子类实例的时候，父类的属性不保存 ##

package com.study.demo.serialize;
    
    import lombok.Data;
    import lombok.ToString;
    
    import java.io.*;
    
    /**
     * Created by e-lipo on 2019/4/23.
     */
    public class SerializeTest3 {
        public static void main(String[] args) {
            Child pf = new Child();
            pf.setPageNum(1);
            pf.setPageSize(10);
            pf.setUserId("l23");
    
            try {
                FileOutputStream fos = new FileOutputStream("e:/serialize.txt");
                ObjectOutputStream oos = new ObjectOutputStream(fos);
                oos.writeObject(pf);
                oos.close();
                System.out.println("序列化: " + pf);//序列化: Child(super=Parent(userId=l23), pageNum=1, pageSize=10)
    
                FileInputStream fis = new FileInputStream("e:/serialize.txt");
                ObjectInputStream ois = new ObjectInputStream(fis);
                Child form = (Child)ois.readObject();
                System.out.println("反序列化: " + form);//反序列化: Child(super=Parent(userId=null), pageNum=1, pageSize=10)
            } catch (Exception e) {
                e.printStackTrace();
            }
    
        }
    }
    
    
    @Data
    class Parent{
        private String userId;
    }
    
    //父类没有实现序列化，子类实现序列化，子类序列化时，父类属性值丢失
    @Data
    @ToString(callSuper = true)
    class Child extends Parent implements Serializable {
        private Integer pageNum;
        private Integer pageSize;
    }

## transient关键字修饰的属性不序列化 ##

package com.study.demo.serialize;
    
    import lombok.Data;
    import lombok.ToString;
    
    import java.io.*;
    
    /**
     * Created by e-lipo on 2019/4/23.
     */
    public class SerializeTest {
        public static void main(String[] args) {
            PageForm pf = new PageForm();
            pf.setPageNum(1);
            pf.setPageSize(10);
            pf.setUserId("l23");
    
            try {
                FileOutputStream fos = new FileOutputStream("e:/serialize.txt");
                ObjectOutputStream oos = new ObjectOutputStream(fos);
                oos.writeObject(pf);
                oos.close();
                System.out.println("序列化: " + pf);//序列化: PageForm(super=BaseForm(userId=l23), pageNum=1, pageSize=10)
    
                FileInputStream fis = new FileInputStream("e:/serialize.txt");
                ObjectInputStream ois = new ObjectInputStream(fis);
                PageForm form = (PageForm)ois.readObject();
                System.out.println("反序列化: " + form);//反序列化: PageForm(super=BaseForm(userId=l23), pageNum=1, pageSize=null)
            } catch (Exception e) {
                e.printStackTrace();
            }
    
        }
    }
    
    //父类实现序列化接口，子类自动序列化
    @Data
    class BaseForm implements Serializable {
        private String  userId;
    }
    
    @Data
    @ToString(callSuper = true)
    class PageForm extends BaseForm {
        private Integer pageNum;
        private transient Integer pageSize;
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21pbmd3dWxpcG8_size_16_color_FFFFFF_t_70]: /images/20220216/df5830164a004eb2b5f3cdbf35565ae1.png