Avalon Framework API 4.3.1 · org.apache.avalon.framework.component.ComponentSelector

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 org.apache.avalon.framework.service.ServiceSelector instead.

Method Summary

Modifier and Type	Method and Description
public boolean	Returns: True if the component exists, False if it does not. hasComponent(Object a string identifying the role to check. hint) Check to see if a `Component` exists for a hint.
public void	release(Component The Component we are releasing. component) Return the `Component` when you are finished with it.
public Component	Returns: the desired component select(Object A hint to retrieve the correct `Component`. hint) Select the `Component` associated with the given hint.

Method Detail

hasComponent back to summary

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

public boolean hasComponent(Object hint)

Check to see if a Component exists for a hint.

Parameters

hint:Object: a string identifying the role to check.

Returns:boolean

True if the component exists, False if it does not.

release back to summary

release	back to summary
public 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:Component The Component we are releasing.

public 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:Component: The Component we are releasing.

select back to summary

select	back to summary
public 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:Object A hint to retrieve the correct `Component`. Returns:Component the desired component Exceptions ComponentException: If the given role is not associated with a `Component`, or a `Component` instance cannot be created.

public 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:Object: A hint to retrieve the correct Component.

Returns:Component

the desired component

Exceptions

ComponentException:: If the given role is not associated with a Component, or a Component instance cannot be created.

public Interface ComponentSelector

Method Summary

Method Detail