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Tuesday, August 05, 2003

HiveMind -- progress

I've been adding more and more to HiveMind in the last couple of days. Yesterday, I added several new translators: extension-point, service, enumerated. I'm keeping the documentation up-to date. I just fixed some latent bugs in Javassist code generation. The code coverage is at 87% (pretty good for 93 files and 5,491 ncloc). I've made recovery from module parsing errors more configurable.

I've added a nifty system to translators called "initializers"; this allows you to say something like "int,min=5" to enforce a minimum value when converting an attribute from a string to an Integer. Each Translator implementation may have a second constructor, which takes a string, and can interpret the string (usually as a list of key value pairs).

There's been some discussion on the Tapestry mailing list about HiveMind. Dave Solis wants meaty examples. Colin Sampaleanu doesn't like the registry part, he wants a more pure IoC (Inversion of Control). You can use HiveMind in an IoC mode, especially with the new translators combined with the BuilderFactory, or you can access the Registry to lookup services and extension points in your own code. I prefer to give options. He also had some good points about testing.

I'm thinking of adding some "deferrment" capability to HiveMind. For example, when you obtain a service, you may get an object that implements the interface, but doesn't talk directly to the service. Instead, as needed, it will ask the service extension point to create the instance (and interceptors) ... that is, on first invocation. Likewise, getExtensionPointElements() may return a List and defer the actual creation of the list of elements until first access.

Just talked with my buddy Prashant and another good thing for HiveMind would be a validator ant task; something that could read all the module deployment descriptors and validate that all contributions to all extension points are valid ... that is, recognized elements, recognized attributes, required attributes provided, and so on.

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