jsf/plugins/org.eclipse.jst.jsf.common/src/org/eclipse/jst/jsf/common/metadata/internal/MetaDataLocatorFactory.java

/*******************************************************************************
 * Copyright (c) 2001, 2007 Oracle Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Oracle Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jst.jsf.common.metadata.internal;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;

import org.eclipse.core.resources.IProject;
import org.eclipse.core.resources.IResourceChangeEvent;
import org.eclipse.core.resources.IResourceChangeListener;
import org.eclipse.core.resources.ResourcesPlugin;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.jst.jsf.common.JSFCommonPlugin;

/**
 * Creates instances of IMetaDataLocators and caches them so that there is only one instance of a particular locator
 * when client requests one. 
 */
public class MetaDataLocatorFactory  
	implements IResourceChangeListener {
	
	private static MetaDataLocatorFactory INSTANCE = null;
	private Map<String, IMetaDataLocator> _locators;
	
	private static final boolean DEBUG = false;
	/**
	 * @return singleton instance of the MetaDataLocatorFactory
	 */
	public synchronized static MetaDataLocatorFactory getInstance(){
		if (INSTANCE == null){
			INSTANCE = new MetaDataLocatorFactory();
			ResourcesPlugin.getWorkspace().addResourceChangeListener(INSTANCE,
			        IResourceChangeEvent.PRE_CLOSE | IResourceChangeEvent.PRE_DELETE);
		}
		return INSTANCE;
	}



	private Map<String, IMetaDataLocator> getLocators() {
		if (_locators == null){
			_locators = new HashMap<String, IMetaDataLocator>();
		}
		return _locators;
	}
	
	/**
	 * @param locatorClassName - may NOT be null
	 * @param bundleId - may NOT be null
	 * @param project - may be null
	 * @return shared instance of IMetaDataLocator 
	 * 			may return null if is IPathSensitiveMetaDataLocator and there is no project context 
	 */
	public IMetaDataLocator getLocator(final String locatorClassName, final String bundleId, final IProject project){
		final Class klass = JSFCommonPlugin.loadClass(locatorClassName, bundleId);
		String key = getKey(locatorClassName, bundleId);
		IMetaDataLocator locator = null;
		try {
			IMetaDataLocator tempLocator = (IMetaDataLocator)klass.newInstance();
			if (tempLocator != null) {				
				if (tempLocator instanceof IPathSensitiveMetaDataLocator) {
					if (project == null)
						return null;
					
					key = getKey(locatorClassName, project.getName());
				}
				
				locator = getLocators().get(key);
				if (locator == null) {
					locator = tempLocator;					
					if (locator instanceof IPathSensitiveMetaDataLocator)
						((IPathSensitiveMetaDataLocator)locator).setProjectContext(project);					
					
					if (DEBUG)
						System.out.println("Created locator: "+locator.toString()); //$NON-NLS-1$
					
					getLocators().put(key, locator);
					locator.startLocating();
				}
			}
		} catch (InstantiationException e) {
			JSFCommonPlugin.log(IStatus.ERROR, "Could not instantiate IMetaDataLocator: "+key, e); //$NON-NLS-1$
		} catch (IllegalAccessException e) {
			JSFCommonPlugin.log(IStatus.ERROR, "IllegalAccessException while creating IMetaDataLocator: "+key, e); //$NON-NLS-1$
		}
		
		return locator;
	}

	/**
	 * @param locatorClassName
	 * @param contextId - this may be the bundleID or the projectName if it is a path sensitive locator
	 * @return key 
	 */
	private String getKey(final String locatorClassName, final String contextId) {
		StringBuffer buf = new StringBuffer(contextId);
		buf.append(":"); //$NON-NLS-1$
		buf.append(locatorClassName);
		return buf.toString();
	}
	
	/**
	 * Stops and disposes all locators
	 */
	public void dispose(){
		ResourcesPlugin.getWorkspace().removeResourceChangeListener(this);
		for (Iterator it=getLocators().values().iterator();it.hasNext();){
			IMetaDataLocator locator = (IMetaDataLocator)it.next();
			locator.stopLocating();			
		}
		getLocators().clear();
	}
	
    /*
     * (non-Javadoc)
     * 
     * @see
     * org.eclipse.core.resources.IResourceChangeListener#resourceChanged(org
     * .eclipse.core.resources.IResourceChangeEvent)
     */
    public void resourceChanged(final IResourceChangeEvent event) {
        if (event.getType() == IResourceChangeEvent.PRE_CLOSE
                || event.getType() == IResourceChangeEvent.PRE_DELETE) {
            // a project is closing - release and cleanup
            final IProject aProject = (IProject) event.getResource();
            
            if (aProject != null) {
            	List<String> locatorsToRemove = new ArrayList<String>();
	    		for (Iterator it=getLocators().keySet().iterator();it.hasNext();){
	    			String key = (String)it.next();	    			
	    			if (locatorIsForProject(key, aProject.getName())) {
	    				locatorsToRemove.add(key);
	    			}
	    		}

	    		if (! locatorsToRemove.isEmpty()) {
	    			for (String key : locatorsToRemove) {
	    				IMetaDataLocator locator = getLocators().get(key);
						
						if (DEBUG)
							System.out.println("Removed locator: "+locator.toString()); //$NON-NLS-1$
	    				
	    				locator.stopLocating();
	    				getLocators().remove(key);
	    			}
	    		}
            }
        }
    }

	private boolean locatorIsForProject(final String key, final String projectName) {
		StringTokenizer t = new StringTokenizer(key, ":"); //$NON-NLS-1$
		String contextId = t.nextToken();
		if (contextId.equals(projectName))
			return true;
		return false;
	}
}