org.apache.avalon.framework.component
Interface ComponentManager

All Known Implementing Classes:

DefaultComponentManager

public interface ComponentManager

A ComponentManager selects Components based on a role. The contract is that all the Components implement the differing roles and there is one Component per role. If you need to select on of many Components that implement the same role, then you need to use a ComponentSelector. Roles are usually the full interface name. 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 different roles:

• InputAdaptor and OutputAdaptor
• Store and Spool

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

Author:

Federico Barbieri, Stefano Mazzocchi, Pierpaolo Fumagalli, Berin Loritsch

See Also:

Component, Composable, ComponentSelector

Method Summary

boolean	hasComponent(java.lang.String role) Check to see if a Component exists for a role.
Component	lookup(java.lang.String role) Get the Component associated with the given role.
void	release(Component component) Return the Component when you are finished with it.

Method Detail

lookup

public Component lookup(java.lang.String role)
                 throws ComponentException

Get the Component associated with the given role. For instance, If the ComponentManager had a LoggerComponent stored and referenced by role, I would use the following call:

 try
 {
     MyComponent log;
     myComponent = (MyComponent) manager.lookup(MyComponent.ROLE);
 }
 catch (...)
 {
     ...
 }
 

Throws:

ComponentException - if an error occurs

hasComponent

public boolean hasComponent(java.lang.String role)

Check to see if a Component exists for a role.

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.