A new binary snapshot of Merlin is now available. The snapshot includes support for the injection of classic avalon lifecycle artifacts via constructor (including Logger, Configuration, Parameters, Context, ServiceManager).
There are no constraints imposed concerning the ordering of lifecycle artifacts (Logger, Configuration, Parameters, Context, ServiceManager).
However, the following restrictions apply:
1. If a single multi-argument constructor is declared the activation
implementation will attempt to populate the constructor relative
to the set of classic Avalon artifacts. If the consutuctor cannot
be fully populated, an exception will be thrown. 2. If a component class declares multiple constructors then
in order to remain compliant with framework 4.1 the activation
implementation will attempt to use a null argument construtor.
If no null argument constructor is found within the set of
available public constructors, an exception will be thrown.In addition to the above - special handling is included for the context artifact. Under the Avalon Meta specification, a component may declare that the supplied context is castable to a particular interface. Under classic Avalon the object implementing the context argument must by definition implement the Avalon Context interface. In the case of a constructor based supply of context - the requirement for the implementation of Avalon Context interface is not implied.
Following a period of experimentation I'm planning on taking a closer look at the Avalon Framework docs to see what (if any) changes are required to support the extended constructor semantics. My initial impression is that represents a change to documentation and no change to actual interfaces. Even so, I have in mind the updating of framework documentation to support constructor based injection under a 4.2 framework release aligned with Avalon Meta 1.4 and Merlin 3.3. Propsals to this effect will be posted to [EMAIL PROTECTED] in due corse. In the meantime this behaviour should be considered as specific to the Avalon Activation framework.
An example the use of constuctor based injection of lifecycle artifacts is included below:
/**
* A widget.
*
* @avalon.component name="widget" lifestyle="singleton"
* @avalon.service type="tutorial.Widget"
*/
public class DefaultWidget implements Widget
{ private final Logger c_logger;
private final Configuration c_config;
private final Gizmo c_gizmo; /**
* Creation of a new widget.
*
* @param logger the assigned logging channel
* @param manager the assigned service manager
* @param config the assigned configuration
*
* @avalon.dependency key="gizmo"
* type="tutorial.Gizmo"
*/
public DefaultWidget (
Logger logger, ServiceManager manager, Configuration config )
throws ServiceException
{
c_logger = logger;
c_config = config;
c_gizmo= (Gizmo) manager.lookup( "gizmo" );
}// plus widget stuff }
A binary download is available under:
http://www.dpml.net/merlin/distributions/3.3/snapshots/20040312/
Cheers, Steve.
--
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