org.apache.avalon.framework.component
Interface ComponentSelector
- All Superinterfaces:
- Component
- All Known Implementing Classes:
- DefaultComponentSelector
- public interface ComponentSelector
- extends Component
A ComponentSelector
selects Component
s based on a
hint. The contract is that all the Component
s 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:
- XMLInputAdaptor and PropertyInputAdaptor
- 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.
- Author:
- Berin Loritsch
- See Also:
Component
,
Composable
,
ComponentManager
Method Summary |
boolean |
hasComponent(java.lang.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(java.lang.Object hint)
Select the Component associated with the given hint. |
select
public Component select(java.lang.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:
name
- A hint to retrieve the correct Component
.- Throws:
ComponentNotFoundException
- If the given role is not associated
with a Component
.ComponentNotAccessibleException
- If a Component
instance cannot be created.
hasComponent
public boolean hasComponent(java.lang.Object hint)
- Check to see if a
Component
exists for a hint.
- Parameters:
role
- a string identifying the role to check.- Returns:
- True if the component exists, False if it does not.
release
public void release(Component component)
- Return the
Component
when you are finished with it. This
allows the ComponentManager
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
ComponentManager system without having to trap Exceptions on a release.
- Parameters:
component
- The Component we are releasing.
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