/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.wicket.markup.renderStrategy;
import org.apache.wicket.Application;
import org.apache.wicket.Component;
import org.apache.wicket.application.HeaderContributorListenerCollection;
import org.apache.wicket.markup.head.IHeaderResponse;
import org.apache.wicket.markup.html.IHeaderContributor;
import org.apache.wicket.markup.html.internal.HtmlHeaderContainer;
import org.apache.wicket.markup.html.internal.HtmlHeaderContainer.HeaderStreamState;
import org.apache.wicket.util.lang.Args;
/**
* An abstract implementation of a header render strategy which is only missing the code to traverse
* the child hierarchy, since the sequence of that traversal is what will make the difference
* between the different header render strategies.
*
* Besides the child hierarchy the render sequence by default (may be changed via subclassing) is as
* follows:
* <ul>
* <li>1. application level headers</li>
* <li>2. the root component's headers</li>
* <li>3. the children hierarchy (to be implemented per subclass)</li>
* </ul>
*
* @author Juergen Donnerstag
*/
public abstract class AbstractHeaderRenderStrategy implements IHeaderRenderStrategy
{
/**
* @return Gets the strategy registered with the application
*/
public static IHeaderRenderStrategy get()
{
// NOT OFFICIALLY SUPPORTED BY WICKET
// By purpose it is "difficult" to change to another render strategy.
// We don't want it to be modifiable by users, but we needed a way to easily test other
// strategies.
String className = System.getProperty("Wicket_HeaderRenderStrategy");
if (className != null)
{
Class<?> clazz = null;
try
{
clazz = Application.get()
.getApplicationSettings()
.getClassResolver()
.resolveClass(className);
if (clazz != null)
{
return (IHeaderRenderStrategy)clazz.newInstance();
}
}
catch (ClassNotFoundException ex)
{
// ignore
}
catch (InstantiationException ex)
{
// ignore
}
catch (IllegalAccessException ex)
{
// ignore
}
}
// Our default header render strategy
// Pre 1.5
// return new ParentFirstHeaderRenderStrategy();
// Since 1.5
return new ChildFirstHeaderRenderStrategy();
}
/**
* Construct.
*/
public AbstractHeaderRenderStrategy()
{
}
@Override
public void renderHeader(final HtmlHeaderContainer headerContainer,
HeaderStreamState headerStreamState, final Component rootComponent)
{
Args.notNull(headerContainer, "headerContainer");
Args.notNull(rootComponent, "rootComponent");
// First the application level headers
renderApplicationLevelHeaders(headerContainer);
// Then the root component's headers
renderRootComponent(headerContainer, headerStreamState, rootComponent);
// Then its child hierarchy
renderChildHeaders(headerContainer, rootComponent);
}
/**
* Render the root component (e.g. Page).
*
* @param headerContainer
* @param headerStreamState
* @param rootComponent
*/
protected void renderRootComponent(final HtmlHeaderContainer headerContainer,
final HeaderStreamState headerStreamState, final Component rootComponent)
{
headerContainer.renderHeaderTagBody(headerStreamState);
rootComponent.internalRenderHead(headerContainer);
}
/**
* Render the child hierarchy headers.
*
* @param headerContainer
* @param rootComponent
*/
abstract protected void renderChildHeaders(final HtmlHeaderContainer headerContainer,
final Component rootComponent);
/**
* Render the application level headers
*
* @param headerContainer
*/
protected final void renderApplicationLevelHeaders(final HtmlHeaderContainer headerContainer)
{
Args.notNull(headerContainer, "headerContainer");
if (Application.exists())
{
HeaderContributorListenerCollection headerContributorListenerCollection =
Application.get().getHeaderContributorListeners();
IHeaderResponse headerResponse = headerContainer.getHeaderResponse();
for (IHeaderContributor listener : headerContributorListenerCollection)
{
listener.renderHead(headerResponse);
}
}
}
}