decoratorfactory.java

displaytag-1.0修正版

/**
 * Licensed under the Artistic License; you may not use this file
 * except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://displaytag.sourceforge.net/license.html
 *
 * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
package org.displaytag.decorator;

import org.displaytag.exception.DecoratorInstantiationException;
import org.displaytag.util.ReflectHelper;


/**
 * Factory for TableDecorator or ColumnDecorator object.
 * @author Fabrizio Giustina
 * @version $Revision: 1.9 $ ($Author: fgiust $)
 */
public final class DecoratorFactory
{

    /**
     * Constructor for DecoratorFactory.
     */
    private DecoratorFactory()
    {
        // unused
    }

    /**
     * If the user has specified a decorator, then this method takes care of creating the decorator (and checking to
     * make sure it is a subclass of the TableDecorator object). If there are any problems loading the decorator then
     * this will throw a DecoratorInstantiationException which will get propagated up to the page.
     * @param decoratorName String full decorator class name
     * @return instance of TableDecorator
     * @throws DecoratorInstantiationException if unable to load specified TableDecorator
     */
    public static TableDecorator loadTableDecorator(String decoratorName) throws DecoratorInstantiationException
    {
        if (decoratorName == null || decoratorName.length() == 0)
        {
            return null;
        }

        try
        {
            Class decoratorClass = ReflectHelper.classForName(decoratorName);
            return (TableDecorator) decoratorClass.newInstance();
        }
        catch (ClassNotFoundException e)
        {
            throw new DecoratorInstantiationException(DecoratorFactory.class, decoratorName, e);
        }
        catch (InstantiationException e)
        {
            throw new DecoratorInstantiationException(DecoratorFactory.class, decoratorName, e);
        }
        catch (IllegalAccessException e)
        {
            throw new DecoratorInstantiationException(DecoratorFactory.class, decoratorName, e);
        }
        catch (ClassCastException e)
        {
            throw new DecoratorInstantiationException(DecoratorFactory.class, decoratorName, e);
        }
    }

    /**
     * If the user has specified a column decorator, then this method takes care of creating the decorator (and checking
     * to make sure it is a subclass of the ColumnDecorator object). If there are any problems loading the decorator
     * then this will throw a DecoratorInstantiationException which will get propagated up to the page.
     * @param columnDecoratorName String full decorator class name
     * @return instance of ColumnDecorator
     * @throws DecoratorInstantiationException if unable to load ColumnDecorator
     */
    public static ColumnDecorator loadColumnDecorator(String columnDecoratorName)
        throws DecoratorInstantiationException
    {
        if (columnDecoratorName == null || columnDecoratorName.length() == 0)
        {
            return null;
        }

        try
        {
            Class decoratorClass = ReflectHelper.classForName(columnDecoratorName);
            return (ColumnDecorator) decoratorClass.newInstance();
        }

        catch (ClassNotFoundException e)
        {
            throw new DecoratorInstantiationException(DecoratorFactory.class, columnDecoratorName, e);
        }
        catch (InstantiationException e)
        {
            throw new DecoratorInstantiationException(DecoratorFactory.class, columnDecoratorName, e);
        }
        catch (IllegalAccessException e)
        {
            throw new DecoratorInstantiationException(DecoratorFactory.class, columnDecoratorName, e);
        }
        catch (ClassCastException e)
        {
            throw new DecoratorInstantiationException(DecoratorFactory.class, columnDecoratorName, e);
        }
    }

}