EJB Server and Container Implementations

Throughout this section, we tried to introduce the EJB concepts that you will need to be familiar with as you go through this book. The concepts can be difficult to grasp and, in some cases, it just takes repeated exposure to the material. So, if you feel that your mind is not clearly focused and these concepts are not quite clear, take a few minutes and quickly scan through this chapter again. It will help you tremendously through the book if you don't have to stop and think about " What is a home object used for again. " This is a great time to get these ideas and concepts solidified in your mind, before we really get into the details of EJB.

The other thing that we want to point out in this wrap-up of the EJB concepts is something like a disclaimer for many things that were discussed in this chapter and that will be discussed later. One of the best things ”or maybe the worst, depending on which side of the enterprise bean you're standing on ”is that the specification is just that, a specification. It provides a framework for vendors to build the necessary and required infrastructure components that help us as bean providers hopefully sleep better at night. This is both good and bad. It's good because vendors have the flexibility to develop the EJB server and container in ways that they think optimize the execution environment. It's also bad because they can develop the EJB server and container in ways they think optimize the execution environment.

Do you get the drift ? Not all server/containers are created equal. Some are open -source projects and good free products to develop and maybe even deploy production applications on. Others are not really ready for prime time, but are good learning environments that don't cost anything to try and sales people won't bother you after downloading it.

The point here is that you must evaluate an EJB server/container based on your set of requirements. Not every project is the same and most have a different set of functional requirements, as well as financial ones. Do the legwork up front and select a vendor that meets your particular requirements. In fact, it's probably wise to select a primary and a secondary vendor, because you most certainly will encounter a customer that refuses to use your primary vendor, regardless of the one that you choose. If you've already selected a secondary EJB vendor, you will look like you really know what you're doing.