[buckminster-dev] Extension point for query resolver factories

[Thomas Hallgren <thomas@xxxxxxx>]

Hi,
I added a new extension point today that makes it possible to register 
new Component Query Resolution strategies. Previously, all we had was a 
Resource Map (the RMAP). Now it will be possible to add completely new 
ways of resolving a query. In addition, I also added the new preference 
'queryResolverSortOrder' to the Buckminster preference store. This 
preference controls the order of execution of registered resolution 
strategies. When more then one strategy is registered, a panel will 
pop-up in the Buckminster preference page that makes it possible to 
change the order and to add/remove strategies.

In order to implement a new strategy, you must write an implementation 
of the org.eclipse.buckminster.core.resolver.IResolutionFactory. This 
factory is responsible for creating instances that implements the 
org.eclipse.buckminster.core.resolver.IResolver interface. Once the 
factory has been created, it must be registered using the 
'org.eclipse.buckminster.core.queryResolvers' extension point.

Here is an example of such a registration:

<extension
      point="org.eclipse.buckminster.core.queryResolvers">
   <queryResolver id="demoRMap">
      <factory 
class="org.eclipse.buckminster.core.resolver.ResourceMapResolverFactory">
         <parameter
               name="resourceMapURL"
               
value="http://www.eclipse.org/buckminster/samples/rmap/demo.rmap"/>
         <parameter
               name="overrideQueryURL"
               value="true"/>
      </factory>
   </queryResolver>
</extension>

Note that the definition allows for parameters. If the implementation is 
derived from org.eclipse.buckminster.core.helpers.AbstractExtension and 
you override the method setExtensionParameter(String key, String value), 
you will get calls to that method. One call for each parameter. The 
order of the calls is undefined. The class 
org.eclipse.buckminster.core.resolver.ResourceMapResolverFactory serves 
as a good reference implementation.

The code is in CVS right now. Will be released shortly.

Kind Regards,
Thomas Hallgren