[strutsit-developer] Again back and contextes

[Manfred W. <ma...@ma...>]

Moin,

Axiom: Everythink that might be a good idea to extend struts is already 
implemented by Craig R. McClanahan. Our ideas from prologistic of 
request/responses in business logic are the goal of a project named 
agility. Description in added on the end of this mail.

Axel has convinced me, that a real back mechanims must save all the 
information, that are used by the step before. That might be:

- Contextes (later on).
- The session informations
- The request informations

My idea was it to force a redirect so the request attributes (not the 
parameter) will be lost. I think thats a good plan first.

I think for context informations we shall use commons-chains, because 
the basic concepts as contextes, commands etc. are implemented in this 
early beta sandbox component. The next step for me is to implement a 
back strategy I has explained some weeks before. When I have checked in 
we can add other concepts like. I need one or two weeks (beside the 
book) to implement it.

Bye
Manfred


      Agility

Agility is a working project name for a business applications framework 
based on the Commons Chain package.

The core idea behind Agility that is as much work as possible should be 
pushed up to the business layer. Input and output is encapsulated with a 
Context object that is passed to and from Agility using a 
ProtocolAdaptor. Depending on its implementation, a ProtocolAdaptor may 
collect input and deliver output directly from the native platform or 
from a presentation framework.

Agility is a Request/Response framework: for each request there is a 
response. The request is encapsulated in a Context object, which 
includes a Command identifier. Each request must correspond to a 
Command, which may also be a Chain of Commands. Commands may nest or 
chain other Commands as needed. The request Command is referred to as 
the "Action".

When a request comes in from the presentation layer (or a presentation 
framework), it is received by a ProtocolAdaptor. The ProtocolAdaptor 
extracts the Action Command name from the native request and consults 
with a ContextFactory to generate a Context for the request. The request 
Context is then passed to the RequestProcessor for the given protocol.

The RequestProcessor is a Command Chain which includes (at a minimum) an 
Action Command. Each protocol can have its own RequestProcessor, which 
may be a combination of protocol-specific and generic commands. The 
Action Command (or Chain) is the core unit of work for the request.

The Action Command may consult business rules and the persistence layer 
to complete the unit of work. Any output or messages generated by the 
Action may be added to the Context under predetermined keys. If the 
Action completes normally, an attribute is added to the Context to 
signify the outcome of the Action. The value of the outcome attribute is 
arbitrary and defined by application implementing the framework 
("success", "failure", "xylophone").

When the RequestProcessor Chain completes, the Context is returned to 
the ProtocolAdaptor. Agility defines the ProtocolAdaptor interface but 
does not provide an implementation. If the ProtocolAdaptor is a simple 
Servlet, it may forward to a server page by munging the outcome value. 
If the ProtocolAdaptor is a presentation layer framework, it may pass 
the value to an internal mechanism that selects or assembles a server 
page, or generates a dynamic response. A ProtocolAdaptor might even 
utilitize its own "ResponseProcessor" to execute a series of Commands to 
assemble an approriate response.


-- 
===========================================
Dipl.-Inf. Manfred Wolff
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