On Tue, 4 Mar 2003 18:14, Peter M. Goldstein wrote:
> Finally, I don't know much about the situation where the Avalon container
> is embedded inside another container that exposes DataSources to its hosted
> applications (i.e. Phoenix inside JBoss, Merlin inside Tomcat), but I don't
> believe those DataSources are made available to Avalon components. Can
> someone clarify this for me? Thanks. If they can't be made available,
> then I would add this as another issue on the list below.
It depends on the container of course but there is no reason why a component
could not be written that that accesses the datasource from JBoss/Tomcate/etc
and provides it to user (actually thats what the datasource component does
iirc).
> First, there is no standard way for a component to access a DataSource.
> There is an implicit binding to another component in the system. So if I
> write a component for one application, and want to reuse it in another, I
> need to ensure that the same method is being used by the second application
> to expose DataSources. This is a coding and not a configuration level
> issue. Most other types of containers have made this a configuration level
> issue using JNDI.
Most other containers dont have strong typing. Basically what I would suggest
is that you create a components whos work interface is DataSource and then
access it via ServiceManager. For each different datasource needed have a
different component instance.
> Second, in this set up one generally has to ensure that the component
> supplying the database connections is at the base of the dependency tree.
> In most systems, data stores are fundamental. So if a database is being
> used, it's important that they be available early. This isn't a huge deal,
> but it simply adds an extra layer to the dependency declarations.
should be handled by container. Just declare a dependency on it and the
container should make sure you get it in correct order.
> Fourth, I would imagine there would be situations where the container may
> want access to data sources for its own purposes (i.e. logging). In the
> current setup container-configured data sources and component-configured
> data sources must be distinct. This seems sub-optimal.
agreed.
Theres a bunch of ideas kicking around how to implement this but none seem to
be killer ideas at this stage.
--
Cheers,
Peter Donald
USER, n.:
The word computer professionals use when they mean "idiot."
-- Dave Barry, "Claw Your Way to the Top"
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