Re: [SUMMARY] Context Concensus

[Paul Hammant]

Leo,

I'd like to summarize shortly the views and proposals that have been put forth, trying to note any equivalence between the proposals and point out where they differ, as well as trying to sort the proposals/views under Avalon4 or Avalon5. For example, Stephen's Locators and Noel's really-big-namespace are interesting ideas, but definitely something for A5. I don't want the ideas to be thrown out but on the other hand it must be understood that these things more deal with a new and better Context, instead of the Context as it is currently being used.

Finally, before I start, I like anyone who feels that their views are being misrepresented here to post a correction. I think there is much more common ground here than what is generally known.

Your rollup is very good.  Again I commend you for the non-partisan effort

[..]

OPERATIONS

There is not concensus on whether the Context should have any active operations. Stephen and Berin, for example, advocates that any active operations should be exposed via the ServiceManager, and that the Context should only be used to fetch data. (Note: By active operations, I mean for example requestShutdown().)

Others point to the Phoenix BlockContext interface.

However, there is concensus that a component should be able to specify any interface that it should be able to cast the context to. That is, for every interface T,

public void contextualize (Context context) {
T myContext = (T) context;
}

[..]

I don't think you have concensus there. I agree this the above should always be possible, but others do not.

STAGED CONTEXTS

This idea has a different context depending on the lifecycle stage:

    public void init (InitContext initContext) { ... };
    public void start (StartupContext startupContext) { ... };
   public void stop (StopContext stopContext) { ... };
    public void dispose (DisposeContext disposeContext) { ... };

I don't like this. It is yet another thing that pushes understanding of A-F further away from newbies. Context is deliberately simple as a contract, yet implementable in weird and wacky ways for specialist containers.

Whilst I have the microphone, I'd like to remind people again that there are live usages of BlockContext out there. They are not in Apache CVS codebases, but in real companies.

- Paul


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