defaultskinfactory.java

jsp + xmｌ实现ｔｒｅｅｖｉｅｗ

/*
 * ====================================================================
 * The JSP Tree Software License, Version 1.1
 *
 * (this license is derived and fully compatible with the Apache Software
 * License - see http://www.apache.org/LICENSE.txt)
 *
 * Copyright (c) 2002-2005 jsptree.sourceforge.net . All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by
 *        jsptree.sourceforge.net (http://jsptree.sourceforge.net/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The name "JSP Tree" must not be used to endorse or promote
 *    products derived from this software without prior written permission.
 *    For written permission, please contact [e-mail] .
 *
 * 5. Products derived from this software may not be called "JSP Tree",
 *    nor may "JSP Tree" appear in their name, without prior written
 *    permission of jsptree.sourceforge.net.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 */

package net.sf.jsptree.skin;

import javax.servlet.jsp.JspTagException;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Represents <i>Factory</i> class, which implements SkinFactory interface.
 * It is a <i>Singleton</i>, since it needs to keep track of whether or not
 * a particular {@link Skin} instance has been generated yet.
 * It then either returns a new instance or a reference to one it
 * has already loaded.
 *
 * @author Vladislav Kamensky
 */
public class DefaultSkinFactory implements SkinFactory {

    private static DefaultSkinFactory m_instace = new DefaultSkinFactory();

    private Skin m_defaultSkin = null;

    private Map m_skins = Collections.synchronizedMap(new HashMap());

    private DefaultSkinFactory() {
        m_defaultSkin = new DefaultTemplateSkin();
        m_skins.put(DefaultTemplateSkin.class.getName(), m_defaultSkin);
    }

    /**
     * @return reference to application's <code>DefaultSkinFactory</code>
     *         instance.
     */
    public static DefaultSkinFactory getInstance() {
        return m_instace;
    }

    /**
     * Returns reference to {@link Skin} instance by specified
     * class name. If such a class has not been loaded yet it
     * returns new instance; otherwise it returns refrence to
     * cached instance.
     *
     * @param p_className The class of {@link Skin} to be returned
     * @return reference to {@link Skin} instance.
     * @throws JspTagException if specified class can not be loaded or
     *                         it does not implement {@link Skin} interface.
     */
    public Skin getSkin(String p_className) throws JspTagException {
        Skin a_skin = (Skin) m_skins.get(p_className);

        if (a_skin != null) {
            return a_skin;
        }
        try {
            a_skin = (Skin) Class.forName(p_className).newInstance();
            m_skins.put(p_className, a_skin);
        } catch (InstantiationException e) {
            throw new JspTagException("Skin: " + p_className + " cann't be instantiated: " + e.getMessage());
        } catch (IllegalAccessException e) {
            throw new JspTagException("Skin: " + p_className + " cann't be instantiated: " + e.getMessage());
        } catch (ClassNotFoundException e) {
            throw new JspTagException("Skin: " + p_className + " cann't be instantiated: " + e.getMessage());
        }
        return a_skin;
    }

    /**
     * Return reference to {@link DefaultTemplateSkin} instance.
     * This type of skin is default for this factory.
     *
     * @return reference to default {@link Skin} instance.
     */
    public Skin getDefaultSkin() {
        return m_defaultSkin;
    }

}