webresource.java

Wicket一个开发Java Web应用程序框架。它使得开发web应用程序变得容易而轻松。 Wicket利用一个POJO data beans组件使得它可以与任何持久层技术相结合。

/*
 * 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.html;

import org.apache.wicket.Resource;
import org.apache.wicket.Response;
import org.apache.wicket.protocol.http.WebResponse;

/**
 * Base class for web resources. See the base class {@link org.apache.wicket.Resource} for details
 * on resources in general, including how they can be shared in an application.
 * 
 * @author Jonathan Locke
 */
public abstract class WebResource extends Resource
{

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * Construct.
	 */
	public WebResource()
	{
		super();
	}

	/**
	 * @see org.apache.wicket.Resource#configureResponse(org.apache.wicket.Response)
	 */
	protected final void configureResponse(final Response response)
	{
		if (response instanceof WebResponse)
		{
			setHeaders((WebResponse)response);
		}
	}

	/**
	 * Subclasses can override this to set there headers when the resource is being served. By
	 * default 2 headers will be set if the Resource is cacheable
	 * 
	 * <pre>
	 * response.setDateHeader(&quot;Expires&quot;, System.currentTimeMillis() + (3600 * 1000));
	 * response.setHeader(&quot;Cache-Control&quot;, &quot;max-age=&quot; + 3600);
	 * </pre>
	 * 
	 * So if a resource wants to control this or doesn't want to set this info it should override
	 * this method and don't call super.
	 * 
	 * @param response
	 *            The WebResponse where set(Date)Header can be called on.
	 */
	protected void setHeaders(WebResponse response)
	{
		if (isCacheable())
		{
			// If time is set also set cache headers.
			response.setDateHeader("Expires", System.currentTimeMillis() +
					(getCacheDuration() * 1000));
			response.setHeader("Cache-Control", "max-age=" + getCacheDuration());
		}
		else
		{
			response.setHeader("Cache-Control", "no-cache, must-revalidate");
		}
	}

	/**
	 * default implementation is to cache resources for 1 hour. can be overridden by extension
	 * classes.
	 * 
	 * @return The cache duration in seconds
	 */
	protected int getCacheDuration()
	{
		return 3600;
	}
}