Inversion of Control Containers and the Dependency Injection pattern

In the Java community there's been a rush of lightweight containers that help to assemble components from different projects into a cohesive application. Underlying these containers is a common pattern to how they perform the wiring, a concept they refer under the very generic name of "Inversion of Control". In this article I dig into how this pattern works, under the more specific name of "Dependency Injection", and contrast it with the Service Locator alternative. The choice between them is less important than the principle of separating configuration from use.

23 January 2004

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DDD_Aggregate

Aggregate is a pattern in Domain-Driven Design. A DDD aggregate is a cluster of domain objects that can be treated as a single unit. An example may be an order and its line-items, these will be separate objects, but it's useful to treat the order (together with its line items) as a single aggregate.

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GetterEradicator

You can tell them by the twitch in the left hand side of the mouth when they see a getter method, there's swift pull on their battleaxe and a satisfied cry as another getter is hewn unmercifully from a class which immediately swoons in an ecstasy of gratefulness at the manly Getter Eradicator's feet.

22 February 2006

bliki

InterfaceImplementationPair

The practice of taking every class and pairing it with an interface. So as a result you see pairs of things - maybe ICustomer and Customer or Customer and CustomerImpl. In many ways it echoes the C/C++ habit of header files for each class, although in this case the interfaces and implementations are actually separate types.

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LazyInitialization

Lazy Initialization is a technique that initializes a variable (in OO contexts usually a field of a class) on it's first access. It canonical form is something like this:

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