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
015package org.apache.tapestry5.internal.services;
016
017import org.apache.tapestry5.internal.structure.Page;
018import 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 */
030public 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}