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
015package org.apache.tapestry.binding;
016
017import org.apache.hivemind.Location;
018import org.apache.hivemind.util.Defense;
019import org.apache.tapestry.BindingException;
020import org.apache.tapestry.IAsset;
021import org.apache.tapestry.IComponent;
022import 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 */
030public class AssetBinding extends AbstractBinding
031{
032    private final IComponent _component;
033
034    private final String _assetName;
035
036    public AssetBinding(String description, ValueConverter valueConverter, Location location,
037            IComponent component, String assetName)
038    {
039        super(description, valueConverter, location);
040
041        Defense.notNull(component, "component");
042        Defense.notNull(assetName, "assetName");
043
044        _component = component;
045        _assetName = assetName;
046    }
047
048    public Object getObject()
049    {
050        IAsset result = _component.getAsset(_assetName);
051
052        if (result == null)
053            throw new BindingException(BindingMessages.missingAsset(_component, _assetName),
054                    _component, getLocation(), this, null);
055
056        return result;
057    }
058
059    public Object getComponent()
060    {
061        return _component;
062    }
063}