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.binding;
016    
017    import org.apache.hivemind.Location;
018    import org.apache.hivemind.util.Defense;
019    import org.apache.tapestry.BindingException;
020    import org.apache.tapestry.IAsset;
021    import org.apache.tapestry.IComponent;
022    import org.apache.tapestry.coerce.ValueConverter;
023    
024    /**
025     * A binding that is connected to an asset provided by a component.
026     * 
027     * @author Howard M. Lewis Ship
028     * @since 4.0
029     */
030    public class AssetBinding extends AbstractBinding
031    {
032        private final IComponent _component;
033    
034        public AssetBinding(String description, ValueConverter valueConverter, Location location,
035                IComponent component, String assetName)
036        {
037            super(assetName, valueConverter, location);
038    
039            Defense.notNull(component, "component");
040            Defense.notNull(assetName, "assetName");
041    
042            _component = component;
043        }
044    
045        public Object getObject()
046        {
047            IAsset result = _component.getAsset(_description);
048    
049            if (result == null)
050                throw new BindingException(BindingMessages.missingAsset(_component, _description),
051                        _component, getLocation(), this, null);
052    
053            return result;
054        }
055    
056        public Object getComponent()
057        {
058            return _component;
059        }
060    }