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kuni katsuya

schuchert - JPA Tutorial 4 - Inheritance and Polymorphic Queries - 0 views

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JPA inheritance PolymorphicQueries

shared by kuni katsuya on 28 Sep 12 - No Cached
  • JPA Tutorial 4 - Inheritance and Polymorphic Queries
  • Books and Dvd's, both of which inherit from Resource
  • When we search for a Resource we might get back Books, Dvd's, or both
  • ...12 more annotations...
  • queries polymorphic
  • Introduce the Resource class
  • new type, Dvd
  • What happens when you perform a query on a type that has subclasses?
  • It turns out support for inheritance in queries (as well as JPA) is built in
  • do not actually need to do anything other than have one entity inherit from another entity to get everything to work
  • book entity inherit from the Resource entity
  • Introduce a new entity type called Resource
  • Change the BookDao to be a ResourceDao
  • Update the methods returning Book and have them instead return Resource
  • Update all references to Book and replace them with Resource
  • Change the bookId to resourceId
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