extensionpointmodel.java

来自「纯java操作系统jnode,安装简单和操作简单的个人使用的Java操作系统」· Java 代码 · 共 185 行

/*
 * $Id: ExtensionPointModel.java,v 1.2 2003/12/21 07:49:02 epr Exp $
 */
package org.jnode.plugin.model;

import java.util.Iterator;
import java.util.Vector;

import nanoxml.XMLElement;

import org.jnode.plugin.Extension;
import org.jnode.plugin.ExtensionPoint;
import org.jnode.plugin.ExtensionPointListener;
import org.jnode.plugin.PluginException;

/**
 * @author epr
 */
public class ExtensionPointModel extends PluginModelObject implements ExtensionPoint {
	
	private final String id;
	private final String uniqueId;
	private final String name;
	private Vector listeners;
	private Extension[] extensionArray;

	private transient Vector extensionsCache;
	
	public ExtensionPointModel(PluginDescriptorModel plugin, XMLElement e) 
	throws PluginException {
		super(plugin);
		id = getAttribute(e, "id", true);
		name = getAttribute(e, "name", true);
		uniqueId = plugin.getId() + "." + id;
		if (id.indexOf('.') >= 0) {
			throw new PluginException("id cannot contain a '.'");
		}
	}

	
	/**
	 * Resolve all references to (elements of) other plugin descriptors
	 * @throws PluginException
	 */
	protected void resolve() 
	throws PluginException {
		// Do nothing
	}
	
	/**
	 * Returns the simple identifier of this extension point. 
	 * This identifier is a non-empty string containing no period 
	 * characters ('.') and is guaranteed to be unique within the 
	 * defining plug-in. 
	 */
	public String getSimpleIdentifier() {
		return id;
	}
	
	/**
	 * Returns the unique identifier of this extension point. 
	 * This identifier is unique within the plug-in registry, and is
	 * composed of the identifier of the plug-in that declared this 
	 * extension point and this extension point's simple identifier. 
	 */
	public String getUniqueIdentifier() {
		return uniqueId;
	}
	
	/**
	 * Gets the human readable name of this extensionpoint
	 */
	public String getName() {
		return name;
	}

	/**
	 * Gets all extensions configured to this extensionpoint.
	 */
	public Extension[] getExtensions() {
		if (extensionArray == null) {
			final Vector cache = getExtensionsCache();
			extensionArray = (Extension[])cache.toArray(new Extension[cache.size()]);
		}
		return extensionArray;
	}
	
	/**
	 * Add a listener
	 * @param listener
	 */
	public void addListener(ExtensionPointListener listener) {
		if (listeners == null) {
			listeners = new Vector();
		}
		listeners.add(listener);
	}
	
	/**
	 * Remove a listener
	 * @param listener
	 */
	public void removeListener(ExtensionPointListener listener) {
		if (listeners != null) {
			listeners.remove(listener);
		}
	}
	
	/**
	 * Add an extension to this point.
	 * @param extension
	 */
	protected void add(Extension extension) {
		final Vector extensions = getExtensionsCache();
		extensions.add(extension);
		// Re-create the array
		extensionArray = null;
		fireExtensionAdded(extension);
	}
	
	/**
	 * Add an extension to this point.
	 * @param extension
	 */
	protected void remove(Extension extension) {
		final Vector extensions = getExtensionsCache();
		extensions.remove(extension);
		extensionArray = null;
		fireExtensionRemoved(extension);
	}
	
	/**
	 * Fire and extensionAdded event to all listeners
	 * @param extension
	 */
	protected void fireExtensionAdded(Extension extension) {
		if (listeners != null) {
			for (Iterator i = listeners.iterator(); i.hasNext(); ) {
				final ExtensionPointListener l = (ExtensionPointListener)i.next();
				l.extensionAdded(this, extension);
			}
		}
	}
	
	/**
	 * Fire and extensionRemoved event to all listeners
	 * @param extension
	 */
	protected void fireExtensionRemoved(Extension extension) {
		if (listeners != null) {
			for (Iterator i = listeners.iterator(); i.hasNext(); ) {
				final ExtensionPointListener l = (ExtensionPointListener)i.next();
				l.extensionRemoved(this, extension);
			}
		}
	}
	
	/**
	 * Gets the extension cache.
	 * This will re-create the cache from the extensionArray if needed.
	 */
	private Vector getExtensionsCache() {
		if (extensionsCache == null) {
			extensionsCache = new Vector();
			if (extensionArray != null) {
				for (int i = 0; i < extensionArray.length; i++) {
					extensionsCache.add(extensionArray[i]);
				}
			}
		}
		return extensionsCache;
	}
	
	/**
	 * @see org.jnode.vm.VmSystemObject#verifyBeforeEmit()
	 */
	public void verifyBeforeEmit() {
		super.verifyBeforeEmit();
		//System.out.println("Cache->Array " + extensionsCache);
		if (extensionsCache != null) {
			extensionArray = (Extension[])extensionsCache.toArray(new Extension[extensionsCache.size()]);
		}
	}
}