java - error marshalling return; -

I get the following exception when I tried to execute my service in my server, which is the EJB2.0 stateless session Bean is positioned in the form of

  Error executing services: error marshaling returns; The nested exception is: java.io.NotSerializableException: xxx.xxx.xxx.PmsService  

here xxx.xxx.xxx.PmsService is my class that already Implemented java.io.Serializable interface

Can you please help me solve it.

MUR

Serialization is a recurring asset; There is no class, and can not be gradual until all its areas can be sorted. Check out your fields for those classes that can not be serialized, and either switch to that range (if it is your own class), switch to a serializeable option, or declare the field as transient (This is the latter case only if it is not in fact part of the object's condition; such as thread, your work is currently running).