hlship-20080520/tapestry-core/src/main/java/org/apache/tapestry/internal/bindings/AssetBindingFactory.java

// Copyright 2007, 2008 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package org.apache.tapestry.internal.bindings;

import org.apache.tapestry.Asset;
import org.apache.tapestry.Binding;
import org.apache.tapestry.ComponentResources;
import org.apache.tapestry.SymbolConstants;
import org.apache.tapestry.ioc.Location;
import org.apache.tapestry.ioc.Resource;
import org.apache.tapestry.ioc.annotation.Symbol;
import org.apache.tapestry.services.AssetSource;
import org.apache.tapestry.services.BindingFactory;

/**
 * Binding factory where the expression is a reference to an asset.
 *
 * @see AssetSource
 */
public class AssetBindingFactory implements BindingFactory
{
    private final AssetSource source;

    private final boolean forceAbsoluteURIs;

    public class AssetBinding extends AbstractBinding
    {
        private final String description;

        private final Asset asset;

        protected AssetBinding(String description, Asset asset, Location location)
        {
            super(location);

            this.description = description;
            this.asset = asset;
        }

        public Object get()
        {
            return asset;
        }

        /**
         * Asset bindings are invariant only if full URIs are being used.  This is complicated ... basically, if the
         * Asset is invariant, then any value coerced from the Asset is also invariant (such as a String version of an
         * Asset's path).  Thus, the invariant String gets cached inside component parameter fields.  However, when the
         * path is dynamic (i.e., because of {@link org.apache.tapestry.internal.services.RequestPathOptimizer}), we
         * need to ensure that the Assets aren't cached.
         *
         * @return true if full URIs are enabled, false otherwise
         */
        @Override
        public boolean isInvariant()
        {
            return forceAbsoluteURIs;
        }

        @Override
        public String toString()
        {
            return String.format("AssetBinding[%s: %s]", description, asset);
        }
    }

    public AssetBindingFactory(AssetSource source,

                               @Symbol(SymbolConstants.FORCE_ABSOLUTE_URIS)
                               boolean forceAbsoluteURIs)
    {
        this.source = source;
        this.forceAbsoluteURIs = forceAbsoluteURIs;
    }

    public Binding newBinding(String description, ComponentResources container, ComponentResources component,
                              String expression, Location location)
    {
        Resource baseResource = container.getBaseResource();

        Asset asset = source.getAsset(baseResource, expression, container.getLocale());

        return new AssetBinding(description, asset, location);
    }
}