This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Can we put all three beans together and make the application work?
Are you talking about the 3 bean types - sesion, message driven and entity? If yes, then i would say it all depends on your application. I have seen applications which usually use Stateless Session beans and Message driven beans. That does not mean that the other types of beans cant be used together.