001    // Copyright 2004, 2005 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry.components;
016    
017    import org.apache.tapestry.AbstractComponent;
018    import org.apache.tapestry.IMarkupWriter;
019    import org.apache.tapestry.IRender;
020    import org.apache.tapestry.IRequestCycle;
021    
022    /**
023     * A component which delegates it's behavior to another object. [<a
024     * href="../../../../../ComponentReference/Delegator.html">Component Reference</a>]
025     * 
026     * @author Howard Lewis Ship
027     */
028    
029    public abstract class Delegator extends AbstractComponent
030    {
031    
032        /**
033         * Gets its delegate and invokes
034         * {@link IRender#render(IMarkupWriter, IRequestCycle)} on it.
035         */
036    
037        protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
038        {
039            IRender delegate = getDelegate();
040            
041            if (delegate != null) delegate.render(writer, cycle);
042        }
043    
044        public abstract IRender getDelegate();
045    }