Something about the ExecutionContext framework has been bugging me over the past few weeks, so today I took a whack at addressing what I perceived to be the problems.  Some of these are outlined in the issue below, but perhaps the biggest problem was in what users/clients saw: the current design seemed to emphasize design/dependency perspective and sacrificed simplicity for the user/client.

The patch outlined below (and attached to the issue) has the changes I'm proposing.  I'm pretty positive about these changes, because I really think it simplifies what users/clients see (including how DNA repositories will be configured).  Basically, the existing ExecutionContext interface is changed to a concrete implementation (with default constructor, and methods to create other instances relative to the context), and ExecutionContext now implements the ExecutionContextFactory interface.  Also, several implementations were removed, and now there really is just one component (ExecutionContext) that users/clients have to worry about.

If you have a chance, please review the patch and provide feedback.  Note that the patch was created using revision 701 (the current revision as of tonight) as a baseline, so it should be easy to grab the latest and apply the patch.

Best regards,

Randall


Begin forwarded message:

From: "Randall Hauch (JIRA)" <jira-events@lists.jboss.org>
Date: January 12, 2009 5:40:03 PM CST
To: dna-issues@lists.jboss.org
Subject: [dna-issues] [JBoss JIRA] Updated: (DNA-270) Simplify the ExecutionContext framework


    [ https://jira.jboss.org/jira/browse/DNA-270?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Randall Hauch updated DNA-270:
------------------------------

   Attachment: dna-270-executioncontext.patch


Attached a patch file that has the proposed changes (relative to revision 701), and which results in all tests passing.

Simplify the ExecutionContext framework
---------------------------------------

               Key: DNA-270
               URL: https://jira.jboss.org/jira/browse/DNA-270
           Project: DNA
        Issue Type: Task
        Components: API, Connectors, Documentation, Examples, Graph, Sequencers
  Affects Versions: 0.3
          Reporter: Randall Hauch
          Assignee: Randall Hauch
           Fix For: 0.4

       Attachments: dna-270-executioncontext.patch


The ExecutionContext interface is used throughout the system.  It's defined in 'dna-graph', and used to represent the context or environment for executing various activities.  There is also ExecutionContextFactory, which is an interface for creating other contexts with different JAAS security contexts (login context or access control contexts).  There are also the Basic* implementations of these interfaces, as well as several subclasses (with various implementations).
The idea of using an interface for this was to simplify the design of the components that uses/took an ExecutionContext, to prevent propagating dependencies, and to allow customization.  However, since ExecutionContext is largely just an aggregation of references, there's little need to customize the behavior, and this doesn't really add any other dependencies to the classpath (all implementations of the aggregated components are already in 'dna-graph') and it doesn't expose any implementations through the method signatures.  Using interfaces also complicates the usage, since clients have to know about the concrete implementations.  This is even more true when they're setting up the DNA services and repositories in 'dna-repository' and 'dna-jcr'.
So, consider changing this interface to a concrete class, with methods that make it easy to create instances as well as instances with custom components (e.g., a new context that is the same as 'this' but with a supplied NamespaceRegistry implementation).
This will change the public API, but this should be acceptable given that we're not yet at 1.0 (and this really improves both the client code, and doesn't really change extension implementations).

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