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.IComponent;
020import org.apache.tapestry.coerce.ValueConverter;
021
022/**
023 * Binding whose value is a named bean provided by a component.
024 * 
025 * @author Howard M. Lewis Ship
026 * @since 4.0
027 */
028public class BeanBinding extends AbstractBinding
029{
030    private final IComponent _component;
031
032    private final String _beanName;
033
034    public BeanBinding(String description, ValueConverter valueConverter, Location location,
035            IComponent component, String beanName)
036    {
037        super(description, valueConverter, location);
038
039        Defense.notNull(component, "component");
040        Defense.notNull(beanName, "beanName");
041
042        _component = component;
043        _beanName = beanName;
044    }
045
046    /**
047     * Beans obtained via the binding should *not* be cached by the component because beans may be
048     * discarded inside the {@link org.apache.tapestry.bean.BeanProvider} based on the life cycle of
049     * the bean.  The BeanProvider caches beans as well.
050     */
051
052    public boolean isInvariant()
053    {
054        return false;
055    }
056
057    public Object getComponent()
058    {
059        return _component;
060    }
061
062    public Object getObject()
063    {
064        return _component.getBeans().getBean(_beanName);
065    }
066
067}