tapestry-framework/src/java/org/apache/tapestry/engine/IPageSource.java

// Copyright 2004, 2005 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.engine;

import org.apache.hivemind.ClassResolver;
import org.apache.tapestry.IPage;
import org.apache.tapestry.IRequestCycle;

/**
 * Abstracts the process of loading pages from thier specifications as well as pooling of pages once
 * loaded.
 * <p>
 * If the required page is not available, a page source may use an instance of {@link IPageLoader}
 * to actually load the page (and all of its nested components).
 * 
 * @author Howard Lewis Ship
 */

public interface IPageSource
{
    /**
     * Gets a given page for the engine. This may involve using a previously loaded page from a pool
     * of available pages, or the page may be loaded as needed.
     * 
     * @param cycle
     *            the current request cycle
     * @param pageName
     *            the name of the page. May be qualified with a library id prefix, which may even be
     *            nested. Unqualified names are searched for extensively in the application
     *            namespace, and then in the framework namespace.
     * @return The loaded page.
     * 
     * @throws org.apache.tapestry.PageNotFoundException
     *             if pageName can't be resolved to a page specification (from which a page instance
     *             can be generated).
     * @see org.apache.tapestry.resolver.PageSpecificationResolver#resolve(IRequestCycle, String)
     */

    IPage getPage(IRequestCycle cycle, String pageName);

    /**
     * Invoked after the engine is done with the page (typically, after the response to the client
     * has been sent). The page is returned to the pool for later reuse.
     *
     * @param page The page to release.
     */
    void releasePage(IPage page);

    /**
     * Gets the class resolver used to load all pages / page components.
     *
     * @return {@link ClassResolver} instance used to load classes. 
     */

    ClassResolver getClassResolver();
}