I have a web application developed using Spring - Struts framework deployed in Tomcat 8 server. The application is hosted in only one server.
The application code is layered like
Action | BPO | DAO | DTO | EntityObject
Only few DTO classes implements Serializable interface where those DTO objects are being written into file using ehcache for caching state.
Do we actually need to implement Serializable interface for all the DTO classes?
With reference to the below link it says not necessary to implement Serializable to all the DTO classes.
DTO implementation of Serializable interface
If so how does the DTO object gets transferred from client side to server side without serialization?
The Serializable is used by java.io and it's needed if you want to keep the objects in session. Some other frameworks is using Serializable behind the scene to perform serialization. If you don't know where the object is serialized using java.io.Serializable you better add this interface to DTOs.
The client-side might use other serialization like JSON, XML, etc., but it doesn't affect the processes running serialization on server-side and it should be handled separately by your code or some other framework like Struts or Spring, doesn't matter.