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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 7713] New: - Optional Implicit precondtion checking in matchers
Date Wed, 03 Apr 2002 10:27:26 GMT
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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=7713

Optional Implicit precondtion checking in matchers

           Summary: Optional Implicit precondtion checking in matchers
           Product: Cocoon 2
           Version: Current CVS
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Enhancement
          Priority: Other
         Component: core
        AssignedTo: cocoon-dev@xml.apache.org
        ReportedBy: michaelm@fztig938.bank.dresdner.net


While writing a large c2 based application we have come across the need for 
matchers with built-in *implicit* checks. 

For Example, instead of using a "valid session checker action" 
in *every* single pipeline in the sitemap to secure against clients 
who do not have sessions, we simply configure a  matcher with a 
"session-exists precondition". That way, we simplify sitemap pipelines, 
which we find are already too large and complex.

There are several advantages with implicit matcher checking including, 
simplified sitemaps,scalablity, easier development with developers not having 
to remember to always include certian actions, hiding of unnecessary and 
repetitive information, etc

Of course precondition matchers are not useful in every situation, 
but are of best advantage when ones finds themselves using the 
same general actions in a lot of the sitemap pipelines.

In this patch we have implemented flexiable matcher precondition checking
which can easly be extended by the developer. Any matcher can now be configured
to use certain specified preconditions when they are declared in the sitemap,
and these in turn may be overridden in the actual matcher pipelines 
with "map:parameter".

AbstractMatcher.java has been introduced which facilitates this new
functionality. All other matchers now directly or indirectly extend 
AbstractMatcher.java.

Note: All new macthers written must extend AbsractMatcher.java to inherit this 
functionality.Also super.match() or super.perparedmatch() or super.configure() 
must be invoked in all new matchers which implement these methods and extend 
from AbstractMatcher.

A conditions directory has been introduced, namely 
cocoon/matching/conditions which contains:-
1.	Condtional.java		(Interface)
2.	UnConditional.java	(boring concrete implementation)
3.	SessionConditional.java (concrete implementation which checks for 
session)

Developers can add there own matcher conditions as long they implement the 
Conditional interface. (Note: Conditional implementations must have zero 
parameter
constructors.)

In sitemap one configures a matcher by using the following tags 
<conditonal>some.class.name</conditional>to set a precondition, or 
<map:parameter name="conditional" value="some.class.name"/> in the actual
matcher pipeline to override default matcher precondition. 

When no conditonal is set, then no precondtions are checked and the matcher 
proceeds as normal. (This means existing cocoon-apps will still function as per 
normal with this patch)

This patch also includes example usage of this new matcher functionaltiy in the 
cocoon sample webapp, under the webapps section. (Click on "Implicit Session 
Checking")

newfiles.tgz contains the new files for this patch.
c2matching.diff contains the diff to be applied.

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