001    // Copyright 2006, 2007, 2008, 2009, 2011 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.tapestry5.internal.services;
016    
017    import org.apache.tapestry5.internal.structure.Page;
018    import org.apache.tapestry5.runtime.PageLifecycleListener;
019    
020    /**
021     * Per-thread service that caches page instances for the duration of the request, and is also responsible for tracking
022     * the active page (the page which will ultimately render the response).
023     * <p/>
024     * Since {@link org.apache.tapestry5.internal.structure.Page} is internal, most user-code should use the
025     * {@link org.apache.tapestry5.services.ComponentSource} service instead.
026     * <p>
027     * Starting in 5.2, page instances are shared (with externalized mutable state), not pooled, but the cache is still
028     * useful for managing the page's {@linkplain PageLifecycleListener lifecycle}.
029     */
030    public interface RequestPageCache
031    {
032        /**
033         * Gets the page via its page name, in the current locale. The logical page name is resolved to a class name, which
034         * is used to obtain the page (from the page pool). Note that under certain circumstances, a page may have multiple
035         * names (even beyond simple case-insensitivity), and RequestPageCache caches correctly.
036         * 
037         * @param pageName
038         *            the name of the page to retrieve (this is the logical page name, not the fully qualified class
039         *            name)
040         * @return a page instance reserved for this request
041         * @throws IllegalArgumentException
042         *             if the name can not be resolved to a page instance
043         */
044        Page get(String pageName);
045    }