Yes. The Java EE spec requires that a Java EE web container be capable of
handling a number of "special" Java EE objects in an HttpSession, including
EJB references. The EJB reference object itself is opaque from the perspective of
the application, so you don't have to worry about whether it explicitly implements
Serializable. Here's the relevant snippet from the spec :
EE.6.4
Web containers must support Java EE distributable web applications placing
objects of any of the following types into a javax.servlet.http.HttpSession
object using the setAttribute or putValue methods:
• java.io.Serializable
• javax.ejb.EJBObject
• javax.ejb.EJBHome
• javax.ejb.EJBLocalObject
• javax.ejb.EJBLocalHome
• javax.transaction.UserTransaction
• a javax.naming.Context object for the java:comp/env context
• a reference to an EJB local or remote business interface
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