All,
I split off the A5 parts of the Context discussion in order to move the A4
part forward toward a proposal. This post contains some minor
clarifications - mostly inclusion of Stephen's and Paul's comments on the
previous summary.
-oOo-
What follows is a *very* brief overview of the ideas that have been shown
on the list. There is no concensus on any of the below solutions.
LOCATORS
These unify all lookup operations. Much as a component can specify what
services it depends on, it can specify what locators it requires. For
example, a ServiceLocator or a SystemLocator. The locator is passed in in
the contextualize() and service() methods, and the component can then cast
the locator to any of the required interfaces before performing the lookup
operations.
void contextualize (Locator locator) {
// Look up services...
ServiceLocator sl = (ServiceLocator) locator;
MyService ms = sl.lookup ("myservice");
...
// Look up context info...
SystemLocator sysLocator = (SystemLocator) locator;
File workDir = sysLocator.locate ("avalon:work");
...
}
The only difference between contextualize() and service() would then be the
ordering in the lifecycle, as this would enable one to lookup services and
context (what used to be) values at both points.
This solution has been somewhat abandoned in favor of the BIG NAMESPACE
solution below.
BIG NAMESPACE
Another way - that also unifies all lookup services - is to have a big
namespace and a Locator interface:
interface Locator {
public Object lookup (String key);
}
where key can be (for example):
service:myservice
context:workDir
jndi:java:/something
urn:something:else
The namespace (service, context, jndi and urn in the example above) would
then be connected to a pluggable namespace handler in the container.
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) { ... };
(
The obvious (to me at least) parallell is:
InitContext -> Context
StartupContext -> ServiceManager
)
Objections to this was raise don the grounds that it is confusing.
/LS
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