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.
024     *
025     *  [<a href="../../../../../ComponentReference/Delegator.html">Component Reference</a>]
026     *
027     *  @author Howard Lewis Ship
028     * 
029     **/
030    
031    public abstract class Delegator extends AbstractComponent
032    {
033        /**
034         *  Gets its delegate and invokes {@link IRender#render(IMarkupWriter, IRequestCycle)}
035         *  on it.
036         *
037         **/
038    
039        protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
040        {
041            IRender delegate = getDelegate();
042            
043            if (delegate != null)
044                    delegate.render(writer, cycle);
045        }
046        
047        public abstract IRender getDelegate();
048    }