DynamicConfigUtil.java

/**
 * (C) Copyright 2013 Jabylon (http://www.jabylon.org) 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
 */
package org.jabylon.common.util.config;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.InvalidRegistryObjectException;
import org.jabylon.common.util.IConfigurationElementLoader;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;

public class DynamicConfigUtil {

    private static Supplier<List<IConfigurationElement>> configSections;
    private static Supplier<List<IConfigurationElement>> configTabs;

    private static final Logger LOG = LoggerFactory.getLogger(DynamicConfigUtil.class);
    
    static{
    	createSuppliers();
    }
    
    private static synchronized void createSuppliers() {
    	configTabs = Suppliers.memoize(Suppliers.compose(new IConfigurationElementLoader(), Suppliers.ofInstance("org.jabylon.rest.ui.configTab")));
    	configSections = Suppliers.memoize(Suppliers.compose(new IConfigurationElementLoader(), Suppliers.ofInstance("org.jabylon.rest.ui.config")));
    	
    }
    
    /**
     * clears the cache of config tabs
     */
    public static void refresh() {
    	LOG.info("Refreshing config contributions");
    	createSuppliers();
    }

    private DynamicConfigUtil() {
        // hide utility constructor
    }

    public static List<IConfigurationElement> getApplicableElements(Object domainObject) {

    	
        List<IConfigurationElement> configSections = getConfigSections();
        
        try {
			List<IConfigurationElement> applicable = new ArrayList<IConfigurationElement>();
			for (IConfigurationElement child : configSections) {

			    if (isApplicable(child, domainObject)) {
			        applicable.add(child);
			    }
			    
			}
			return applicable;
		} catch (InvalidRegistryObjectException e) {
			LOG.warn("Failed to retrieve config extensions. Reloading",e);
			createSuppliers();
			List<IConfigurationElement> applicableElements = getApplicableElements(domainObject);
			LOG.warn("Reload complete",e);
			return applicableElements;
		}
    }

    private static boolean isApplicable(IConfigurationElement child, Object domainElement) {
        String objectClass = child.getAttribute("objectClass");

        try {
            Class<?> clazz = Class.forName(objectClass);
            return clazz.isInstance(domainElement);
        } catch (ClassNotFoundException e) {
            // TODO: this will not work for arbitrary classes. Need to explode
            // super classes and interfaces of the domain object
            e.printStackTrace();
            return false;
        }

    }

    public static List<IConfigurationElement> getConfigSections() {
        return configSections.get();
    }

    public static List<IConfigurationElement> getConfigTabs() {
        return configTabs.get();
    }
}