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Java Forum / JavaBeans / May 2005How implement this find method with bean inheritence?
I have a ProductBean which is the super class of BookBean, ClothesBean and I want to create a find method like: [CODE]public ProductRemote findAllInCategory(Integer categoryID) throws FinderException, RemoteException;[/CODE] Since each bean is going to have its own table, what's the best way to do this? Is this even possible with CMP find methods? >I have a ProductBean which is the super class of BookBean, ClothesBean > and I want to create a find method like: [quoted text clipped - 4 lines] > Since each bean is going to have its own table, what's the best way to > do this? Is this even possible with CMP find methods? Yes you can do it with cmp but I believe the current ejb spec does not allow home interfaces to be inherited. Therefore you need to declare your findAllInCategory() method in the interface in each bean. You can then simply hard code the category id in the ejbql for each method in your descriptors and simply call the method on the correct home interface runtime type. (This is where a factory might come in useful to automatically get you the correct type.) The bean implementation and business methods can be inherited but the homes currently must extend EJBHome or EJBLocalHome according to the spec, that's what makes this tricky. > You can then simply hard code the category id in the ejbql > for each method in your descriptors But I can't do that because if I have 2 different types of products (say Books and Magazines) but they're both in the category "Print Items," then I need to return two different Entity types. I know this can be done in EJB 3.0, but how would I do it in 2.0? Both entities will be stored in diff. tables from each other in the DB. Obviously, I could do it in BMP, but I'd like to do it in CMP. Is there a way to do it? >> You can then simply hard code the category id in the ejbql >> for each method in your descriptors [quoted text clipped - 7 lines] > Obviously, I could do it in BMP, but I'd like to do it in CMP. Is there > a way to do it? You could return a collection of print items in your printItems home, e.g. with a query using "where categoryId IN(bookId, magazineId)". You would be able to cast each item in the collection to printItem but not to book or magazine. I thnk the only way you can make this work sensibly is if your inheritance tree follows you categorization i.e. you have books and magazines extending printItems thus allowing you to group these items together. If they are in separate tables i.e. not differentiated by an id column in the same table, then they are different types of object and presumably have different attribues/behaviour and I'm not then sure why you'd want to get them by a category id, maybe you could look at your design and find a better way to do this e.g. jst amalgamate the collections of each type in a wrapper method to work with them from there. You can have abstract schemas defined in your descriptor for a cmp bean that extend over many tables but how this is done may well depend on your j2ee server. 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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