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.bean;
016    
017    import org.apache.tapestry.IBinding;
018    
019    /**
020     *  A helper bean to assist with providing defaults for unspecified
021     *  parameters.    It is initalized
022     *  with an {@link IBinding} and a default value.  It's value property
023     *  is either the value of the binding, but if the binding is null,
024     *  or the binding returns null, the default value is returned.
025     *
026     *  @author Howard Lewis Ship
027     *  @since 1.0.5
028     * 
029     **/
030    
031    public class Default
032    {
033        private IBinding binding;
034        private Object defaultValue;
035    
036        public void resetForPool()
037        {
038            binding = null;
039            defaultValue = null;
040        }
041    
042        public void setBinding(IBinding value)
043        {
044            binding = value;
045        }
046    
047        public IBinding getBinding()
048        {
049            return binding;
050        }
051    
052        public void setDefaultValue(Object value)
053        {
054            defaultValue = value;
055        }
056    
057        public Object getDefaultValue()
058        {
059            return defaultValue;
060        }
061    
062        /**
063         *  Returns the value of the binding.  However, if the binding is null, or the binding
064         *  returns null, then the defaultValue is returned instead.
065         *
066         **/
067    
068        public Object getValue()
069        {
070            if (binding == null)
071                return defaultValue;
072    
073            Object value = binding.getObject();
074    
075            if (value == null)
076                return defaultValue;
077    
078            return value;
079        }
080        
081        /** @since 3.0 **/
082        
083        public void discardFromPool()
084        {
085        }
086    
087    }