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Java Forum / General / September 2006EnterpriseBean and finalize()
Hi Everyone, I'm trying to learn EJB and picked up a copy of the book "SCBCD Exam Study Kit" by Paul Sanghera. Inside it, I came across the following sentence, which piqued my interest because I cannot see a) where this can be found in the EJB 2.0 specification (actually, I was looking in the J2EE 1.3 specification), or b) why finalizing a bean would be interfering with the responsibilities of the container. Here's the quote: "... the bean class must not have any finalize() method because by doing this you would be stepping on the container's toes, since it is the responsibility of the container to manage the lifecycle, threads, garbage collection, and so forth." If anyone can shed a little light on this, and dispel the confusion, I'd really appreciate it. Many thanks, Jono > Hi Everyone, > I'm trying to learn EJB and picked up a copy of the book "SCBCD Exam [quoted text clipped - 12 lines] > If anyone can shed a little light on this, and dispel the confusion, > I'd really appreciate it. Certainly, entity bean instances may be pooled. If those instances have 'finalize' methods, then it would be invoked at some potentially very inconvenient times for the container, and almost certainly much later than the programmer intended. On the other hand, there are certain events that can cause an instance to expelled from the pool, and the 'finalize' method would eventually be called on the instance (much sooner than the programmer intended). Programming with beans means letting the container do a lot of the work. A 'finalize' method interferes with work that the container is supposed to be doing for you. -- Adam Maass > I'm trying to learn EJB and picked up a copy of the book "SCBCD Exam > Study Kit" by Paul Sanghera. Inside it, I came across the following [quoted text clipped - 8 lines] > the responsibility of the container to manage the lifecycle, threads, > garbage collection, and so forth." The EJB 2.1 spec has: 7.11.2 Session Bean Class ... • The class must not define the finalize() method. so it is in the spec. Next question is why. EJB's has a long list of restrictions on what they are allowed to use. The general intention is to make sure that EJB are so well behaving that they will work in all application servers and will not exhibit bad characteristics compared to expectations of a business component. I can not see any specific reason for this particular restriction. But I can not see any reason to have a finalize method either. It does not make any sense in the context an EJB is used. Arne Thank you for your answers to both of my questions. I'm guessing that the restriction wasn't a part of the 2.0 spec and as such is misleading in a book written to help people pass the SCBCD exam, but I can imagine how it might increase the stability of enterprise beans in more current versions of the specification. It's a pity that Sun only offer certification on such an old version of this EJB technology - it would feel far more rewarding to know you were certified in the cutting edge Java EE. Jono > > I'm trying to learn EJB and picked up a copy of the book "SCBCD Exam > > Study Kit" by Paul Sanghera. Inside it, I came across the following [quoted text clipped - 32 lines] > > Arne > Thank you for your answers to both of my questions. I'm guessing that > the restriction wasn't a part of the 2.0 spec and as such is misleading [quoted text clipped - 4 lines] > feel far more rewarding to know you were certified in the cutting edge > Java EE. The EJB 2.0 spec says exactly the same: 7.10.2 Session bean class The following are the requirements for session bean class: ... • The class must not define the finalize() method. Arne Thanks for pointing that out, Arne. In my haste to wrap things up on Friday, I had done a quick search for "finalize" in the wrong specification. Regards, Jono > > Thank you for your answers to both of my questions. I'm guessing that > > the restriction wasn't a part of the 2.0 spec and as such is misleading [quoted text clipped - 13 lines] > > Arne Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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