iheaderresponse.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.ResourceReference;
import org.apache.wicket.Response;

/**
 * Interface that is used to render header elements (usually javascript and CSS references).
 * 
 * Implementation of this interface is responsible for filtering duplicate contributions (so that
 * for example the same javascript is not loaded twice) during the same request.
 * 
 * @author Matej Knopp
 */
public interface IHeaderResponse
{
	/**
	 * Writes a javascript reference, if the specified reference hasn't been rendered yet.
	 * 
	 * @param reference
	 *            resource reference pointing to the javascript resource
	 */
	public void renderJavascriptReference(ResourceReference reference);

	/**
	 * Writes a javascript reference, if the specified reference hasn't been rendered yet.
	 * 
	 * @param reference
	 *            resource reference pointing to the javascript resource
	 * @param id
	 *            id that will be used to filter duplicate reference (it's still filtered by URL
	 *            too)
	 */
	public void renderJavascriptReference(ResourceReference reference, String id);

	/**
	 * Writes a javascript reference, if the specified reference hasn't been rendered yet.
	 * 
	 * @param url
	 *            url of the the javascript resource
	 */
	public void renderJavascriptReference(String url);

	/**
	 * Writes a javascript reference, if the specified reference hasn't been rendered yet.
	 * 
	 * @param url
	 *            url of the the javascript resource
	 * @param id
	 *            id that will be used to filter duplicate reference (it's still filtered by URL
	 *            too)
	 */
	public void renderJavascriptReference(String url, String id);


	/**
	 * Renders javascript code to the response, if the javascript has not already been rendered.
	 * 
	 * the necessary surrounding <code>script</code> tags will be added to the output.
	 * 
	 * @param javascript
	 *            javascript content to be rendered.
	 * 
	 * @param id
	 *            unique id for the javascript element. This can be null, however in that case the
	 *            ajax header contribution can't detect duplicate script fragments.
	 */
	public void renderJavascript(CharSequence javascript, String id);

	/**
	 * Writes a CSS reference, if the specified reference hasn't been rendered yet.
	 * 
	 * @param reference
	 *            resource reference pointing to the CSS resource
	 */
	public void renderCSSReference(ResourceReference reference);

	/**
	 * Writes a CSS reference, if the specified reference hasn't been rendered yet.
	 * 
	 * @param url
	 *            url of the CSS resource
	 */
	public void renderCSSReference(String url);

	/**
	 * Writes a CSS reference, if the specified reference hasn't been rendered yet.
	 * 
	 * @param reference
	 *            resource reference pointing to the CSS resource
	 * @param media
	 *            the media type for this CSS ("print", "screen", etc.)
	 */
	public void renderCSSReference(ResourceReference reference, String media);

	/**
	 * Writes a CSS reference, if the specified reference hasn't been rendered yet.
	 * 
	 * @param url
	 *            url of the CSS resource
	 * @param media
	 *            the media type for this CSS ("print", "screen", etc.)
	 */
	public void renderCSSReference(String url, String media);

	/**
	 * Renders an arbitrary string to the header. The string is only rendered if the same string
	 * hasn't been rendered before.
	 * <p>
	 * Note: This method is kind of dangerous as users are able to write to the output whatever they
	 * like.
	 * 
	 * @param string
	 *            string to be rendered to head
	 */
	public void renderString(CharSequence string);

	/**
	 * Marks the given object as rendered. The object can be anything (string, resource reference,
	 * etc...). The purpose of this function is to allow user to manually keep track of rendered
	 * items. This can be useful for items that are expensive to generate (like interpolated text).
	 * 
	 * @param object
	 *            object to be marked as rendered.
	 */
	public void markRendered(Object object);

	/**
	 * Returns whether the given object has been marked as rendered.
	 * <ul>
	 * <li>Methods <code>renderJavascriptReference</code> and <code>renderCSSReference</code>
	 * mark the specified {@link ResourceReference} as rendered.
	 * <li>Method <code>renderJavascript</code> marks List of two elements (first is javascript
	 * body CharSequence and second is id) as rendered.
	 * <li>Method <code>renderString</code> marks the whole string as rendered.
	 * <li>Method <code>markRendered</code> can be used to mark an arbitrary object as rendered
	 * </ul>
	 * 
	 * @param object
	 *            Object that is queried to be rendered
	 * @return Whether the object has been marked as rendered during the request
	 */
	public boolean wasRendered(Object object);

	/**
	 * Returns the response that can be used to write arbitrary text to the head section.
	 * <p>
	 * Note: This method is kind of dangerous as users are able to write to the output whatever they
	 * like.
	 * 
	 * @return Response
	 */
	public Response getResponse();

	/**
	 * Renders javascript that is executed right after the DOM is built, before external resources
	 * (e.g. images) are loaded.
	 * 
	 * @param javascript
	 */
	public void renderOnDomReadyJavascript(String javascript);

	/**
	 * Renders javascript that is executed after the entire page is loaded.
	 * 
	 * @param javascript
	 */
	public void renderOnLoadJavascript(String javascript);

	/**
	 * Renders javascript that is executed after the given event happens on specified target
	 * 
	 * @param target
	 * @param event
	 * @param javascript
	 */
	public void renderOnEventJavacript(String target, String event, String javascript);

	/**
	 * Mark Header rendering is completed and subsequent usage will be ignored. If some kind of
	 * buffering is used internally, this action will mark that the contents has to be flushed out.
	 */
	public void close();

	/**
	 * @return if header rendering is completed and subsequent usage will be ignored
	 */
	boolean isClosed();
}