schuchert - JPA Tutorial 4 - Inheritance and Polymorphic Queries - 0 views
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JPA Tutorial 4 - Inheritance and Polymorphic Queries
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Books and Dvd's, both of which inherit from Resource
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When we search for a Resource we might get back Books, Dvd's, or both
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queries polymorphic
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Introduce the Resource class
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new type, Dvd
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What happens when you perform a query on a type that has subclasses?
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It turns out support for inheritance in queries (as well as JPA) is built in
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do not actually need to do anything other than have one entity inherit from another entity to get everything to work
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book entity inherit from the Resource entity
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Introduce a new entity type called Resource
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Change the BookDao to be a ResourceDao
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Update the methods returning Book and have them instead return Resource
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Update all references to Book and replace them with Resource
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Change the bookId to resourceId