序列化继承

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

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;
}