org.apache.avalon.framework.service

Interface ServiceSelector

public interface ServiceSelector

A ServiceSelector selects Objects based on a supplied policy. The contract is that all the Objects implement the same role.

Version: $Id: ServiceSelector.java 30977 2004-07-30 03:57:54 -0500 (Fri, 30 Jul 2004) niclas $

Author: Avalon Development Team

Method Summary
boolean	isSelectable(Object policy) Check to see if a Object exists relative to the supplied policy.
void	release(Object object) Return the Object when you are finished with it.
Object	select(Object policy) Select the Object associated with the given policy.

Method Detail

isSelectable

public boolean isSelectable(Object policy)

Check to see if a Object exists relative to the supplied policy.

Parameters: policy a Object containing the selection criteria

Returns: True if the component is available, False if it not.

Return the Object when you are finished with it. This allows the ServiceSelector to handle the End-Of-Life Lifecycle events associated with the Object. Please note, that no Exception should be thrown at this point. This is to allow easy use of the ServiceSelector system without having to trap Exceptions on a release.

Parameters: object The Object we are releasing, may also be a null reference

select

public Object select(Object policy)

Select the Object associated with the given policy. For instance, If the ServiceSelector has a Generator stored and referenced by a URL, the following call could be used:

 try
 {
     Generator input;
     input = (Generator)selector.select( new URL("foo://demo/url") );
 }
 catch (...)
 {
     ...
 }

Parameters: policy A criteria against which a Object is selected.

Returns: an Object value

Throws: ServiceException If the requested Object cannot be supplied