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

  • Field Details

  • Constructor Details

    • Registry

      public Registry()
      Create a new empty registry.

  • Method Details

    • 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, ClassLoader classLoader)
      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).
      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
      classLoader - The class loader that "owns" the event handler. The class loader is requried to be able to automatically unregister event handlers when an extension is uninstalled or updated. If null, automatic unloading is disabled (beware of memory leaks!).
      Since:
      3.10

    • unregisterEventHandler

      public void unregisterEventHandler(EventHandler eventHandler)
      Unregisters an event handler.
      Parameters:
      eventHandler - The event handler
      Since:
      2.8

    • unregisterEventHandlers

      public void unregisterEventHandlers(ClassLoader classLoader)
      Unregister all event handlers that was loaded by the given class loader. This method should be called when an extension file is being uninstalled or updated since the old registered event handlers can then no longer be used and it is really complicated for an extension that register event handler to detect a re-installation property. It is better to try to handle this at the core level.
      Parameters:
      classLoader - The class loader that is responsible for the extension file that is about to be uninstalled or updated
      Since:
      3.10

    • 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, ClassLoader classLoader)
      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
      classLoader - The class loader that is responsible for loading classes for the extension point, or null if the default class loader should be used
      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
      Since:
      3.2

    • 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 ExtensionPoint object or null if that extension point doesn't exists

    • getExtensionPoints

      public List<ExtensionPoint<?>> getExtensionPoints()
      Get a list with all registered extension points. The returned list is a copy of the registered extension points at the time of this call and will not reflect changes made to the registry after this call has returned.
      Returns:
      A list
      Since:
      3.0 (Returned an Iterator in BASE 2.x)

    • 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, ClassLoader classLoader)
      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
      classLoader - The class loader that is responsible for loading classes for the extension, or null if the default class loader should be used
      Throws:
      InvalidUseOfNullException - If the extension is null, or if the ID or action factory is null
      Since:
      3.2

    • 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 List<Extension<?>> getExtensions()
      Get a list with all registered extensions. The returned list is a copy of the registered extensions at the time of this call and will not reflect changes made to the registry after this call has returned.
      Returns:
      A list
      Since:
      3.0 (Returned an Iterator in BASE 2.x)

    • getExtensions

      public List<Extension<?>> getExtensions(String id)
      Get a list with all registered extensions for a given extension point. If the extension point is not found an empty list is returned. The returned list is a copy of the registered extension points at the time of this call and will not reflect changes made to the registry after this call has returned.
      Parameters:
      id - The ID of the extension point
      Returns:
      A list
      Since:
      3.0 (Returned an Iterator in BASE 2.x)

    • useExtensions

      public <A extends Action> ExtensionsInvoker<A> 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 ExtensionPoint.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.