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https://issues.apache.org/jira/browse/CHAIN-51?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Niall Pemberton updated CHAIN-51:
---------------------------------
Attachment: CHAIN-51-Alternative-Listener-proposal.patch
I have some comments about your suggestions - but before that Commons Chain is
pretty dormant - I did the last bugfix release back in May 2008, but Chain
hasn't had any real development since at least 2006. It would probably be a
good idea to try to find a committer willing to commit your work, before
putting any more effort on this - otherwise you may be wasting your time.
Having said that, here are my comments.
There is some general work needed to your contribution before it would be ready
to commit. If you fixed them and re-submitted, then it would reduce the work
needed to be done by a committer and probably increase the chances that it
would be accepted:
* Create a patch (rather than rar file) - see
http://commons.apache.org/patches.html
* Change the package names from your "ar.com.santiagobasulto" to
"org.apache.commons.chain"
* Add the ASF license headers to your source files:
http://www.apache.org/legal/src-headers.html
* The tests are currently mixed in with the rest of the source code - move
them to follow the commons chain directory structure (tests are in
"src/test/java") and make them JUnit tests like the rest of Chain's tests
In its current form your contribution requires a minimum of JDK 1.6 and Commons
Chain is currently supporting a minimum of JDK 1.3. Changing the minimum JDK
version is probably not going to be an issue - but the only thing in your work
that requires JDK 1.6 rather than JDK 1.5 is the use of @Override markers for
implementations of interfaces (which JDK 1.5 doesn't allow). I think JDK 1.5
would be a good minimum version and removing @Override for interface
implementations would not be a great loss.
I have some comments about the implementation in general - apologies, they are
probably disorganized and some may contradict others(!) - but here goes:
* I would drop the PaneHandler and StreamHandler implementations - I think
those implementations are too specific for a Commons component and don't add
enough value to be included
* I don't like the way the new Action interface extends the existing
Command interface - which then requires a new ActionChain interface to provide
the Chain equivalent. IMO it would be better to have this as a completely
separate interface that any Command or Chain could implement. To make that
workable requires adding a "get" method for the handler/listeners
* I think it would be better to use the java's "listener" concept
* rename Action to CommandHandler and
* rename ActionHandler to CommandListener and extend the EventListener
marker interface
* Create a CommandEvent object that extends EventObject and is used as
a parameter to the listener methods
* Remove the "fail" method from the listener and add "Exception" as a
property of CommandEvent. The "done" method then gets called whether the
execution is successful or throws an exception.
* We could then modify the existing ChainBase to implement CommandHandler
and call listeners for itself and for the Commands it executes. This way
anything using ChainBase would get this automatically built in
{code}
public interface CommandHandler {
void addListener(CommandListener c);
boolean removeListener(CommandListener c);
Iterable<CommandListener> getListeners();
}
{code}
{code}
public interface CommandListener extends EventListener {
void start(CommandEvent event);
void finish(CommandEvent event);
}
{code}
{code}
public class CommandEvent extends EventObject {
private final Context context;
private final Exception exception;
public CommandEvent(Command command, Context context, Exception exception) {
super(command);
this.context = context;
this.exception = exception;
}
public Context getContext() {
return context;
}
public Exception getException() {
return exception;
}
}
{code}
> New Features for the project.
> -----------------------------
>
> Key: CHAIN-51
> URL: https://issues.apache.org/jira/browse/CHAIN-51
> Project: Commons Chain
> Issue Type: New Feature
> Reporter: Santiago Basulto
> Attachments: actions-src.rar,
> CHAIN-51-Alternative-Listener-proposal.patch
>
> Original Estimate: 240h
> Remaining Estimate: 240h
>
> I'm proposing a change to the project. Did not know how to do it, so asked in
> the mailing list and told me to make the proposal here.
> I'll comment a little about my changes. It needs a lot of refactoring and
> documenting, but i'd like to comment the main idea behind it, so you can give
> your opinion. I have faced some problems with names. I did not want to rename
> commons.chain classes, as a matter of respect, so some names can seem weird,
> it can change.
> First of all, i needed more "control" over my commands. I like to have
> everything logged, and several commands were used in GUI apps, so i needed
> more User interaction. Then, i decide to provide the main Interface (Command)
> some other methods, just to can track what is it doing. I made a new
> interface called Action (i use the other name given to this pattern). I
> extend it from Command, just becouse i didn't want to change everything, and
> can keep using my old Commands.
> This new Interface, Action, has two new methods:
> void registerHandler(ActionHandler c);
> boolean removeHandler(ActionHandler c); //true if the handler was
> present, false otherwise
> The main idea behind this was to have a Handler object that can track the
> "moves and states" of the Action (or Command) class. It's something similar
> to the Observer Pattern. An action "can" (optionally, if doesn't want to
> register a handler, it's a simple Command) register a Handler, and comunicate
> things about itself. So, i have an Interface called ActionHandler. It has
> three methods:
>
> void start(Action a);
> void done(Action a);
> void fail(Action a,Exception e);
> Then, for example, the action "can" invoke start method from its handler, to
> comunicate it that has started executing. It's really simple, but helped me
> big time.
> Something great about the Action Interface, is that it only sais that you can
> register a handler, not the number of handlers. So, a Class implementing
> Action can register a number of handlers (file logger handler, GUI tool for
> comunicating the user, console logger, etc) and inform about the progress to
> all of them. If it's not needed to comunicate, this class can just execute
> silently.
> So, this is the main change, but with this little change i needed to do
> something with the chain. So i just made the Chain interface extend the
> Action interface. Of course, can be another class, something like ActionChain
> that implements the Action Interface, and let Chain untouched.
> I've attached a simpler version of my source code. With just the basic
> classes and a package for test it. I've developed some other classes, for
> example, Action implementations that register several ActionHandlers. I'm
> currently working on a "BlockingQueueChain", it's a chain that can execute
> all its Commands (or Actions) in parallel. Obviusly, there are not so many
> cases when this Chain can be used. If someone is interested i will can send
> the source code.
> Ok, i think that's all. Hope you can tell me if this is a good idea, or not.
> Or simply, whether i should start a new "branch" of the project to no
> interfere with Commons Chain.
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