001// Copyright 2004, 2005 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry.callback;
016
017import org.apache.hivemind.util.Defense;
018import org.apache.tapestry.IPage;
019import org.apache.tapestry.IRequestCycle;
020
021/**
022 * Simple callback for returning to a page.
023 * <p>
024 * Example usage of <tt>PageCallback</tt>:
025 * <p>
026 * The Home page ensure a user is authenticated in the
027 * {@link org.apache.tapestry.IPage#validate(IRequestCycle)} method. If the user is not
028 * authenticated, they are redirected to the Login page, after setting a callback in the Login page.
029 * <p>
030 * The Login page <tt>formSubmit()</tt> {@link org.apache.tapestry.IActionListener} authenticates
031 * the user and then invokes {@link ICallback#performCallback(IRequestCycle)} to the Home page.
032 * 
033 * <pre>
034 * 
035 *  
036 *    public class Home extends BasePage {
037 *   
038 *        public void validate(IRequestCycle cycle) {            
039 *            Visit visit = (Visit) getVisit();
040 *        
041 *            if (!visit.isAuthenticated()) {
042 *                Login login = (Login) cycle.getPage(&quot;Login&quot;);
043 *  
044 *                login.setCallback(new PageCallback(this));
045 *                
046 *                throw new PageRedirectException(login);
047 *            }            
048 *        }
049 *    }
050 *  
051 *    public Login extends BasePage {
052 *   
053 *        private ICallback _callback;
054 *  
055 *        public void setCallback(ICallback _callback) {
056 *            _callback = callback;
057 *        }
058 *  
059 *        public void formSubmit(IRequestCycle cycle) {
060 *            // Authentication code
061 *            ..
062 *     
063 *            Visit visit = (Visit) getVisit();
064 *  
065 *            visit.setAuthenticated(true);
066 *    
067 *            if (_callback != null) {
068 *                _callback.performCallback(cycle);
069 *            }
070 *        }
071 *    }    
072 *    
073 *  
074 * </pre>
075 * 
076 * @author Howard Lewis Ship
077 * @since 0.2.9
078 */
079
080public class PageCallback implements ICallback
081{
082    /**
083     * @since 2.0.4
084     */
085
086    private static final long serialVersionUID = -3286806776105690068L;
087
088    private String _pageName;
089
090    public PageCallback(String pageName)
091    {
092        Defense.notNull(pageName, "pageName");
093        _pageName = pageName;
094    }
095
096    public PageCallback(IPage page)
097    {
098        Defense.notNull(page, "page");
099
100        _pageName = page.getPageName();
101    }
102
103    public String toString()
104    {
105        return "PageCallback[" + _pageName + "]";
106    }
107
108    /**
109     * Invokes {@link IRequestCycle#activate(String)} to select the previously identified page as
110     * the response page.
111     */
112
113    public void performCallback(IRequestCycle cycle)
114    {
115        Defense.notNull(cycle, "cycle");
116
117        cycle.activate(_pageName);
118    }
119}