Package org.apache.avalon.framework.component

Interface ComponentSelector

All Superinterfaces:
Component
All Known Implementing Classes:
DefaultComponentSelector, WrapperComponentSelector
public interface ComponentSelector extends Component
A ComponentSelector selects Components based on a hint. The contract is that all the Components implement the same role.

A role is better understood by the analogy of a play. There are many different roles in a script. Any actor or actress can play any given part and you get the same results (phrases said, movements made, etc.). The exact nuances of the performance is different.

Below is a list of things that might be considered the same role:

  • XMLInputAdapter and PropertyInputAdapter
  • FileGenerator and SQLGenerator

The ComponentSelector does not specify the methodology of getting the Component, merely the interface used to get it. Therefore the ComponentSelector can be implemented with a factory pattern, an object pool, or a simple Hashtable.

Deprecated: Use ServiceSelector instead.

Version:
CVS $Revision: 1.21 $ $Date: 2004/02/11 14:34:24 $
Author:
Avalon Development Team
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    hasComponent(Object hint)
    Check to see if a Component exists for a hint.
    void
    release(Component component)
    Return the Component when you are finished with it.
    Component
    select(Object hint)
    Select the Component associated with the given hint.

  • Method Details

    • select

      Component select(Object hint) throws ComponentException
      Select the Component associated with the given hint. For instance, If the ComponentSelector has a Generator stored and referenced by a URL, I would use the following call: 
       try
 {
     Generator input;
     input = (Generator)selector.select( new URL("foo://demo/url") );
 }
 catch (...)
 {
     ...
 }
      Parameters:
      hint - A hint to retrieve the correct Component.
      Returns:
      the desired component
      Throws:
      ComponentException - If the given role is not associated with a Component, or a Component instance cannot be created.

    • hasComponent

      boolean hasComponent(Object hint)
      Check to see if a Component exists for a hint.
      Parameters:
      hint - a string identifying the role to check.
      Returns:
      True if the component exists, False if it does not.

    • release

      void release(Component component)
      Return the Component when you are finished with it. This allows the ComponentSelector to handle the End-Of-Life Lifecycle events associated with the Component. Please note, that no Exceptions should be thrown at this point. This is to allow easy use of the ComponentSelector system without having to trap Exceptions on a release.
      Parameters:
      component - The Component we are releasing.