net.sf.basedb.util.extensions
Class Registry

java.lang.Object
  net.sf.basedb.util.extensions.Registry

public class Registry
extends Object

A registry for keeping track of extensions points and installed extensions. Extension points and extensions can, for example, be created programmatically using the ExtensionPointBean and ExtensionBean implementations, or loaded from an XML extension definition file with the XmlLoader class. Applications may provide other means of creating and registering extensions and extensions points.

Version:

2.7

Author:

nicklas

See Also:

ExtensionsDirectory

Last modified

$Date:2008-03-20 12:15:25 +0100 (Thu, 20 Mar 2008) $

Nested Class Summary

(package private) static class	Registry.AttributeKey Identifies attribute.
(package private) static class	Registry.RegisteredAbout
(package private) static class	Registry.RegisteredExtension<A extends Action> Internal representation of an extension.
(package private) static class	Registry.RegisteredExtensionPoint<A extends Action> Internal representation of an extension point.

Field Summary

private Map<Registry.AttributeKey,Object>	attributes
private static ExtensionsFilter	DEFAULT_FILTER Default filter implementation for useExtensions(ClientContext, ExtensionsFilter, String...)
private ErrorHandlerFactory<Action>	defaultErrorHandlerFactory
private Map<EventHandler,EventFilter>	eventHandlers
private static Comparator<ExtensionPoint<?>>	EXTENSIONPOINT_COMPARATOR
private Map<String,Registry.RegisteredExtensionPoint<?>>	extensionPoints
private Map<String,Registry.RegisteredExtension<?>>	extensions
private static Logger	log

Constructor Summary

Registry()
Create a new empty registry.

Method Summary

boolean	extensionIsRegistered(String id) Checks if an extension is registered or not.
boolean	extensionPointIsRegistered(String id) Checks if an extension point is registered or not.
Object	getAttribute(String id, String name) Get the value of a extra attribute for a registered extension or extension point.
ErrorHandlerFactory<Action>	getDefaultErrorHandlerFactory() Get the default error handler factory.
Extension<?>	getExtension(String id) Get the extension with a given ID.
ExtensionPoint<?>	getExtensionPoint(String id) Get the extension point with a given ID.
Iterator<ExtensionPoint<?>>	getExtensionPoints() Get an iterator returning all registered extension points.
Iterator<Extension<?>>	getExtensions() Get an iterator returning all registered extensions.
Iterator<Extension<?>>	getExtensions(String id) Get an iterator returning all registered extensions for a given extension point.
Throwable	getLastExtensionError(String id) Get information about the last error that happened when rendering an extension.
Throwable	getLastExtensionPointError(String id) Get information about the last error that happened when rendering an extension point.
void	handleEvent(EventType eventType, ExtensionPoint<?> extensionPoint, Extension<?> extension) Send an event to all event handlers.
void	registerEventHandler(EventHandler eventHandler, EventFilter filter) Register an event handler for responding to events happening to extension points and extensions in the registry.
<A extends Action> void	registerExtension(Extension<A> extension) Register an extension.
<A extends Action> void	registerExtensionPoint(ExtensionPoint<A> extensionPoint) Register an extension point.
void	setAttribute(String id, String name, Object value) Set an extra attribute on a registered extension or extension point.
void	setDefaultErrorHandlerFactory(ErrorHandlerFactory<Action> defaultErrorHandlerFactory) Set the default error handler factory.
void	unregisterEventHandler(EventHandler eventHandler) Unregisters an event handler.
void	unregisterExtension(String id) Unregister an extension.
void	unregisterExtensionPoint(String id) Unregister an extension point.
ExtensionsInvoker<?>	useExtensions(ClientContext clientContext, ExtensionsFilter filter, String... extensionPointIds) Use extensions from one or more extension points.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

log

private static final Logger log

EXTENSIONPOINT_COMPARATOR

private static final Comparator<ExtensionPoint<?>> EXTENSIONPOINT_COMPARATOR

extensionPoints

private final Map<String,Registry.RegisteredExtensionPoint<?>> extensionPoints

extensions

private final Map<String,Registry.RegisteredExtension<?>> extensions

attributes

private Map<Registry.AttributeKey,Object> attributes

eventHandlers

private Map<EventHandler,EventFilter> eventHandlers

defaultErrorHandlerFactory

private ErrorHandlerFactory<Action> defaultErrorHandlerFactory

DEFAULT_FILTER

private static final ExtensionsFilter DEFAULT_FILTER

Default filter implementation for useExtensions(ClientContext, ExtensionsFilter, String...)

Constructor Detail

Registry

public Registry()

Create a new empty registry.

Method Detail

setDefaultErrorHandlerFactory

public void setDefaultErrorHandlerFactory(ErrorHandlerFactory<Action> defaultErrorHandlerFactory)

Set the default error handler factory.

Parameters:

defaultErrorHandlerFactory - Null is not allowed

Since:

2.17

getDefaultErrorHandlerFactory

public ErrorHandlerFactory<Action> getDefaultErrorHandlerFactory()

Get the default error handler factory.

Since:

2.17

getAttribute

public Object getAttribute(String id,
                           String name)

Get the value of a extra attribute for a registered extension or extension point.

Parameters:

id - The ID of a registered extension or extension point

name - The name of the attribute

Returns:

The attribute value or null if no value has been set

setAttribute

public void setAttribute(String id,
                         String name,
                         Object value)

Set an extra attribute on a registered extension or extension point.

Parameters:

id - The ID of a registered extension or extension point

name - The name of the attribute

value - The attribute value. A null value removes the attribute.

registerEventHandler

public void registerEventHandler(EventHandler eventHandler,
                                 EventFilter filter)

Register an event handler for responding to events happening to extension points and extensions in the registry. The registry itself sends the events listed below. Other events may be sent externally by calling handleEvent(EventType, ExtensionPoint, Extension).

• EventType.AFTER_REGISTRATION
• EventType.BEFORE_UPDATE
• EventType.AFTER_UPDATE
• EventType.BEFORE_UNREGISTRATION

  Parameters:

  eventHandler - The handler that should be called

  filter - A filter that determines which events that should be sent to the handler, or null to send all events

  Since:

  2.8

unregisterEventHandler

public void unregisterEventHandler(EventHandler eventHandler)

Unregisters an event handler.

Parameters:

eventHandler - The event handler

Since:

2.8

handleEvent

public void handleEvent(EventType eventType,
                        ExtensionPoint<?> extensionPoint,
                        Extension<?> extension)

Send an event to all event handlers.

Parameters:

eventType - The event type

extensionPoint - The extension point the event is about

extension - The extension the event is about, or null

Since:

2.8

extensionPointIsRegistered

public boolean extensionPointIsRegistered(String id)

Checks if an extension point is registered or not.

Parameters:

id - The ID of the extension point

Returns:

TRUE if an extension point with the given ID is registered, FALSE otherwise

registerExtensionPoint

public <A extends Action> void registerExtensionPoint(ExtensionPoint<A> extensionPoint)

Register an extension point. If the extension point already exists, the description and renderer factory is updated. The action class can't be changed for a registered extension point. The registry keeps it's own internal representation of the extension point. Changes to the object passed as a parameter to this method will not be reflected in the registry.

Parameters:

extensionPoint - The extension point to register

Throws:

InvalidUseOfNullException - If the extension point is null, or if the ID or actionClass is null

ClassCastException - If the action class doesn't implement the Action interface

unregisterExtensionPoint

public void unregisterExtensionPoint(String id)

Unregister an extension point. If the extension point doesn't exists, nothing is done. This method will also unregister all extensions that extends the given extension point.

Parameters:

id - The ID of the extension point to unregister

Throws:

InvalidUseOfNullException - If the ID is null

getExtensionPoint

public ExtensionPoint<?> getExtensionPoint(String id)

Get the extension point with a given ID.

Parameters:

id - The ID of the extension point

Returns:

An Registry.RegisteredExtensionPoint object or null if that extension point doesn't exists

getExtensionPoints

public Iterator<ExtensionPoint<?>> getExtensionPoints()

Get an iterator returning all registered extension points. The returned iterator doesn't support removal and will not reflect changes made to the registry by the same or other threads after this call has returned.

Returns:

An iterator object

extensionIsRegistered

public boolean extensionIsRegistered(String id)

Checks if an extension is registered or not.

Parameters:

id - The ID of the extension

Returns:

TRUE if an extension with the given ID is registered, FALSE otherwise

getLastExtensionPointError

public Throwable getLastExtensionPointError(String id)

Get information about the last error that happened when rendering an extension point.

Parameters:

id - The id of the extension point

Returns:

The error, or null if no error information is available

Since:

2.9

registerExtension

public <A extends Action> void registerExtension(Extension<A> extension)

Register an extension. If the extension is already registered, the description, position, action factory and renderer factory is updated. The registry keeps it's own internal representation of the extension. Changes made to the object passed as a parameter to this method will not be reflected in the registry.

Parameters:

extension - The extension to register

Throws:

InvalidUseOfNullException - If the extension is null, or if the ID or action factory is null

unregisterExtension

public void unregisterExtension(String id)

Unregister an extension. If the extension point doesn't exists, nothing is done.

Parameters:

id - The ID of the extension to unregister

Throws:

InvalidUseOfNullException - If the ID is null

getExtension

public Extension<?> getExtension(String id)

Get the extension with a given ID.

Parameters:

id - The ID of the extension point

Returns:

An Extension object or null if that extension doesn't exists

getLastExtensionError

public Throwable getLastExtensionError(String id)

Get information about the last error that happened when rendering an extension.

Parameters:

id - The id of the extension

Returns:

The error, or null if no error information is available

Since:

2.9

getExtensions

public Iterator<Extension<?>> getExtensions()

Get an iterator returning all registered extensions. The returned iterator doesn't support removal and will not reflect changes made to the registry by the same or other threads after this call has returned.

Returns:

An iterator object

getExtensions

public Iterator<Extension<?>> getExtensions(String id)

Get an iterator returning all registered extensions for a given extension point. If the extension point is not found an empty iterator is returned. The returned iterator doesn't support removal and will not reflect changes made to the registry by the same or other threads after this call has returned.

Parameters:

id - The ID of the extension point

Returns:

An iterator object

useExtensions

public ExtensionsInvoker<?> useExtensions(ClientContext clientContext,
                                          ExtensionsFilter filter,
                                          String... extensionPointIds)

Use extensions from one or more extension points. This method will return an invoker object that allows the use and rendering of extensions for one or more extension points. The context object should have been initialised with information about the currently logged in user and, depending on the application, some information about what it about to happen. For example, that we are going to display a list of samples.

Each extension that has been registered with the extension points will get a chance to check the context object and to further initialise it with extension-dependent information. This is a task for the ActionFactory.prepareContext(InvokationContext) method. If this method returns false the extension will not be included in the invoker. Extensions may for example use this to check if the logged in user has enough permissions to be able to use the extension.

If the extension points and/or extensions also provide renderer factories, the RendererFactory.prepareContext(InvokationContext) is called. For renderer factories that are attached to extension points the method is only called if at least one enabled extension exists. If the method is called, it is only called once with a null argument for the extension. Renderer factories that are attached to extensions are called once for each enabled extension, but only if the extension point allows renderer overriding. See Registry.RegisteredExtensionPoint.allowRendererOverride().

The returned invoker will not reflect changes made to the registry by the same or other threads after this call has returned. Each use/invokation of an extension point should call this method to get a new invoker object.

Parameters:

clientContext - Information about the current context

filter - A filter object that can be used to filter out disabled extensions and sort the extensions in a particular order. If this value is null, no extensions are filtered out and they are sorted according to their Extension.getIndex() value

extensionPointIds - An array of extension point ID:s to get extension for. In most cases the extension points should require the same action class but this is not required if the extension point renderer can handle more than one action type. Extension points that are not found are ignored.