Package no.sesat.commons.ioc

This package provides a supporting utility, ContextWrapper, for Inversion of Control pattern in schibsted søk code.

See:
Description

Interface Summary

BaseContext

The Base Context all contexts describing a class's contextual 'inversion-of-control' (dependencies) must extend.

Class Summary

ContextWrapper

Utility class to create Proxy wrappers to a single defined context class from a list of context subclasses.

Package no.sesat.commons.ioc Description

This package provides a supporting utility, ContextWrapper, for Inversion of Control pattern in schibsted søk code.

This is a pure design pattern that is independant of IoC frameworks.
For more information read Examining the validity of Inversion of Control

Each class that requires dependencies defines these dependencies in an inner interface named "Context". The class then accepts an implementation of this Context in it's constructor(s) and uses the context to perform those dependencies that it should not take responsibility for.

The major flaw, and hence reason for this package, is that, because the contextual IoC requires you to implement the Context in the calling code, the calling code ends up very verbose with lots of anonymous classes inside constructor calls. In a highly depth-wise IoC implementation many of these Context anonymous class implementations will just be delegating to the next context(s) up.
This last verbosity explosion can be avoided by using the ContextWrapper utility to create a java.util.reflect.Proxy class implementing the required Context and automatically delegating back to the next context(s) up.

One requirement of ContextWrapper is that the returning context and list of contexts that will be delegated to must all extend the BaseContext interface.
This is solely for type-safety.