Interface FilterChain

All Superinterfaces:
Collection<Filter>, Iterable<Filter>, List<Filter>, Processor<Context>
All Known Implementing Classes:
AbstractFilterChain, DefaultFilterChain, ListFacadeFilterChain

public interface FilterChain extends Processor<Context>, List<Filter>

This class implement the "Chain of Responsibility" pattern (for more info, take a look at the classic "Gang of Four" design patterns book). Towards that end, the Chain API models a computation as a series of "protocol filter" that can be combined into a "protocol chain".

The API for Filter consists of a two set of methods (handleXXX() and postXXX) which is passed a "protocol context" parameter containing the dynamic state of the computation, and whose return value is a NextAction that instructs FilterChain, how it should continue processing. The owning ProtocolChain must call the postXXX() method of each Filter in a FilterChain in reverse order of the invocation of their handleXXX() methods.

The following picture describe how it Filter(s)

 
 -----------------------------------------------------------------------------
 - Filter1.handleXXX() --> Filter2.handleXXX()                    |          -
 -                                                                |          -
 -                                                                |          -
 -                                                                |          -
 - Filter1.postXXX() <-- Filter2.postXXX()                        |          -
 -----------------------------------------------------------------------------
 
 

The "context" abstraction is designed to isolate Filter implementations from the environment in which they are run (such as a Filter that can be used in either IIOP or HTTP parsing, without being tied directly to the API contracts of either of these environments). For Filter that need to allocate resources prior to delegation, and then release them upon return (even if a delegated-to Filter throws an exception), the "postXXX" method can be used for cleanup.

Author:
Jeanfrancois Arcand, Alexey Stashok
See Also: