// 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.pageload;
import org.apache.hivemind.ClassResolver;
import org.apache.tapestry.IEngine;
import org.apache.tapestry.IPage;
import org.apache.tapestry.IRequestCycle;
import org.apache.tapestry.Tapestry;
import org.apache.tapestry.engine.IPageLoader;
import org.apache.tapestry.engine.IPageSource;
import org.apache.tapestry.resolver.PageSpecificationResolver;
import org.apache.tapestry.services.ObjectPool;
import org.apache.tapestry.util.MultiKey;
/**
* A source for pages for a particular application. Each application should have its own
* <code>PageSource</code>, storing it into the {@link javax.servlet.ServletContext}using a
* unique key (usually built from the application name).
* <p>
* The <code>PageSource</code> acts as a pool for {@link IPage}instances. Pages are retrieved
* from the pool using {@link #getPage(IRequestCycle, String, IMonitor)}and are later returned to
* the pool using {@link #releasePage(IPage)}.
* <p>
* TBD: Pooled pages stay forever. Need a strategy for cleaning up the pool, tracking which pages
* have been in the pool the longest, etc.
*
* @author Howard Lewis Ship
*/
public class PageSource implements IPageSource
{
/** set by container. */
private ClassResolver _classResolver;
/** @since 4.0 */
private PageSpecificationResolver _pageSpecificationResolver;
/** @since 4.0 */
private IPageLoader _loader;
/**
* The pool of {@link IPage}s. The key is a {@link MultiKey}, built from the page name and the
* page locale. This is a reference to a shared pool.
*/
private ObjectPool _pool;
public ClassResolver getClassResolver()
{
return _classResolver;
}
/**
* Builds a key for a named page in the application's current locale.
*/
protected MultiKey buildKey(IEngine engine, String pageName)
{
Object[] keys;
keys = new Object[]
{ pageName, engine.getLocale() };
// Don't make a copy, this array is just for the MultiKey.
return new MultiKey(keys, false);
}
/**
* Builds a key from an existing page, using the page's name and locale. This is used when
* storing a page into the pool.
*/
protected MultiKey buildKey(IPage page)
{
Object[] keys;
keys = new Object[]
{ page.getPageName(), page.getLocale() };
// Don't make a copy, this array is just for the MultiKey.
return new MultiKey(keys, false);
}
/**
* Gets the page from a pool, or otherwise loads the page. This operation is threadsafe.
*/
public IPage getPage(IRequestCycle cycle, String pageName)
{
IEngine engine = cycle.getEngine();
Object key = buildKey(engine, pageName);
IPage result = (IPage) _pool.get(key);
if (result == null)
{
_pageSpecificationResolver.resolve(cycle, pageName);
// The loader is responsible for invoking attach(),
// and for firing events to PageAttachListeners
result = _loader.loadPage(
_pageSpecificationResolver.getSimplePageName(),
_pageSpecificationResolver.getNamespace(),
cycle,
_pageSpecificationResolver.getSpecification());
}
else
{
// But for pooled pages, we are responsible.
// This call will also fire events to any PageAttachListeners
result.attach(engine, cycle);
}
return result;
}
/**
* Returns the page to the appropriate pool. Invokes {@link IPage#detach()}.
*/
public void releasePage(IPage page)
{
Tapestry.clearMethodInvocations();
page.detach();
Tapestry.checkMethodInvocation(Tapestry.ABSTRACTPAGE_DETACH_METHOD_ID, "detach()", page);
_pool.store(buildKey(page), page);
}
/** @since 4.0 */
public void setPool(ObjectPool pool)
{
_pool = pool;
}
/** @since 4.0 */
public void setClassResolver(ClassResolver resolver)
{
_classResolver = resolver;
}
/** @since 4.0 */
public void setPageSpecificationResolver(PageSpecificationResolver resolver)
{
_pageSpecificationResolver = resolver;
}
/** @since 4.0 */
public void setLoader(IPageLoader loader)
{
_loader = loader;
}
}