why actionform is implements serializable ?

[Ayan Dutta]

Hi ,
My query is why actionform implements serializable ? like any other class as it implements serializable ,it then can be serialized .But why we need that ? In most cases whatever persistance is required, we just take the form bean field values(i.e the properties) and persist them in the DB .Then why the formbean itself implements serializable ?
Regards,
Ayan

[Merrill Higginson]

The J2EE Servlet spec states that any object that is stored in an HTTPSession object should implement Serializable. The reason for this is that application servers in a distributed environment may need to serialize sessions for storage in a Database or transmission to a different JVM. Since One of the valid scopes for an ActionForm is session, it has to be serializable in order to meet this requirement.

[Ayan Dutta]

ok .Thanks for the answer .
I have query then,I can also store any Object ,say a simple Integer Object and in that I can store that using session.setAttribute(integerVariableName), but I think Integer Object does not implement serializable ? But still it can be stored in the session .
then why it is stored then ?
Regards,
Ayan

[Purushoth Thambu]

Ayan, If you look at the JDK api doc on Integer object you will find that this object and all other wrapper objects does implements Serializable.
Regarding why ActionsForms implements serializable:

- ActionForms can be stored in "session" scope. (refer struts-config.xml) and as Merrill said the session cannot be replicated to secondary server for failover if all the objects in session does not implements Serializable interface.

- However, if you application runs on just one server then you are free to objects which doesn't implement serializable interface in session. But this uncommon now.
[ October 31, 2006: Message edited by: Purushothaman Thambu ]