net.smartlab.web.PropertiesEnumeration Maven / Gradle / Ivy

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/*
 * The SmartWeb Framework
 * Copyright (C) 2004-2006
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * For further informations on the SmartWeb Framework please visit
 *
 *                        http://smartweb.sourceforge.net
 */
package net.smartlab.web;

import java.lang.reflect.Constructor;
import java.net.URL;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;
import java.util.TreeMap;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * This class allows to use a properties file to define enumeration elements but
 * needs the definition of two public constructors. Implementors of this class need to
 * define two constructors: one without parameters which simply calls
 * super() and an additional one taking two strings and calling
 * super(String, String).
 * 
 * @author rlogiacco
 */
public abstract class PropertiesEnumeration extends StringEnumeration {

	private static final long serialVersionUID = 228095287903246251L;

	private static final Class[] TYPES = new Class[] {String.class, String.class};

	private static Map enumerations = new HashMap();

	/**
	 * Provides logging capabilities.
	 */
	protected final static Log logger = LogFactory.getLog(PropertiesEnumeration.class);


	/**
	 * The empty public constructor which MUST be exposed by subclasses.
	 */
	public PropertiesEnumeration() {
		super();
	}

	/**
	 * The parametrized public constructor which MUST be exposed by subclasses.
	 *
	 * @param code the enumeration element code
	 * @param display the enumeration element display name
	 */
	public PropertiesEnumeration(String code, String display) {
		super(code, display);
	}

	/**
	 * @see net.smartlab.web.StringEnumeration#decode(java.lang.String)
	 */
	public StringEnumeration decode(String code) {
		if (logger.isDebugEnabled()) {
			logger.debug("decode(\"" + code + "\") - start");
		}
		Map values = (Map)enumerations.get(this.getClass());
		if (values == null) {
			synchronized (this.getClass()) {
				try {
					String classname = this.getClass().getName();
					URL url = this.getClass().getResource(
							classname.substring(classname.lastIndexOf('.') + 1) + ".properties");
					Properties properties = new Properties();
					properties.load(url.openStream());
					Iterator entries = properties.entrySet().iterator();
					Constructor instantiator = this.getClass().getConstructor(TYPES);
					values = new TreeMap();
					while (entries.hasNext()) {
						Map.Entry entry = (Map.Entry)entries.next();
						if (logger.isTraceEnabled()) {
							logger.trace("   adding (" + entry.getKey() + ", " + entry.getValue() + ")");
						}
						values.put(entry.getKey(), instantiator.newInstance(new Object[] {entry.getKey(),
								entry.getValue()}));
					}
					enumerations.put(this.getClass(), values);
				} catch (NoSuchMethodException nsme) {
					logger.fatal("missing constructor " + this.getClass().getName() + "(String, String)", nsme);
				} catch (Exception e) {
					logger.error("decode() - failed", e);
				}
			}
		}
		return (StringEnumeration)values.get(code);
	}
}