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Showing posts from August 1, 2012

Dynamic CDI producers

CDI has the well known concept of producers. Simply put a producer is a kind of general factory method for some type. It's defined by annotating a method with @Produces. An alternative "factory" for a type is simply a class itself; a class is a factory of objects of its own type. In CDI both these factories are represented by the Bean type. The name may be somewhat confusing, but a Bean in CDI is thus not directly a bean itself but a type used to create instances (aka a factory). An interesting aspect of CDI is that those Bean instances are not just internally created by CDI after encountering class definitions and producer methods, but can be added manually by user code as well. Via this mechanism we can thus dynamically register factories, or in CDI terms producers. This can be handy in a variety of cases, for instance when a lot of similar producer methods would have to be defined statically, or when generic producers are needed. Unfortunately, generics are not pa…