java bean如果不进行序列化会发生什么?

代码参考：https://www.jb51.net/article/118646.htm

什么是序列化？将对象的状态信息转换为可以存储或传输的形式的过程，在序列化期间，对象将其当前状态写入到临时存储区或持久性存储区，之后，便可以通过从存储区中读取或反序列化对象的状态信息，来重新创建该对象。

java序列化的例子：

public class Employee implements java.io.Serializable
{
    public String name;
    public String address;
    public transient int SSN;
    public int number;
    public void mailCheck()
    {
        System.out.println("Mailing a check to " + name
                + " " + address);
    }
}

public class SerializeDemo
{
    public static void main(String [] args)
    {
        Employee e = new Employee();
        e.name = "Reyan Ali";
        e.address = "Phokka Kuan, Ambehta Peer";
        e.SSN = 11122333;
        e.number = 101;
        try
        {
            FileOutputStream fileOut =
                    new FileOutputStream("p://employee.ser");
            ObjectOutputStream out = new ObjectOutputStream(fileOut);
            out.writeObject(e);
            out.close();
            fileOut.close();
            System.out.println("Serialized data is saved in employee.ser");
        }catch(IOException i)
        {
            i.printStackTrace();
        }
    }
}

反序列化：

import java.io.*;
public class DeserializeDemo
{
    public static void main(String [] args)
    {
        Employee e = null;
        try
        {
            FileInputStream fileIn = new FileInputStream("p://employee.ser");
            ObjectInputStream in = new ObjectInputStream(fileIn);
            e = (Employee) in.readObject();
            in.close();
            fileIn.close();
        }catch(IOException i)
        {
            i.printStackTrace();
            return;
        }catch(ClassNotFoundException c)
        {
            System.out.println("Employee class not found");
            c.printStackTrace();
            return;
        }
        System.out.println("Deserialized Employee...");
        System.out.println("Name: " + e.name);
        System.out.println("Address: " + e.address);
        System.out.println("SSN: " + e.SSN);
        System.out.println("Number: " + e.number);
    }
}

以上代码正常执行，如果改为：

public class Employee
{
    public String name;
    public String address;
    public transient int SSN;
    public int number;
    public void mailCheck()
    {
        System.out.println("Mailing a check to " + name
                + " " + address);
    }
}

则写入文件时会报错：

java.io.NotSerializableException: com.Employee
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
    at com.sunlands.community.api.message.REST.SerializeDemo.main(SerializeDemo.java:24)

第24行代码报错：即：out.writeObject(e);