1 /*
2 * $Id: EventActionDispatcher.java 471754 2006-11-06 14:55:09Z husted $
3 *
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 package org.apache.struts.actions;
23
24 import java.util.StringTokenizer;
25 import java.lang.reflect.Method;
26
27 import javax.servlet.ServletException;
28 import javax.servlet.http.HttpServletRequest;
29 import javax.servlet.http.HttpServletResponse;
30
31 import org.apache.commons.logging.Log;
32 import org.apache.commons.logging.LogFactory;
33 import org.apache.struts.action.Action;
34 import org.apache.struts.action.ActionForm;
35 import org.apache.struts.action.ActionMapping;
36 import org.apache.struts.action.ActionForward;
37
38 /**
39 * <p>An Action helper class that dispatches to to one of the public methods
40 * that are named in the <code>parameter</code> attribute of the corresponding
41 * ActionMapping and matches a submission parameter. This is useful for
42 * developers who prefer to use many submit buttons, images, or submit links
43 * on a single form and whose related actions exist in a single Action class.</p>
44 *
45 * <p>The method(s) in the associated <code>Action</code> must have the same
46 * signature (other than method name) of the standard Action.execute method.</p>
47 *
48 * <p>To configure the use of this action in your
49 * <code>struts-config.xml</code> file, create an entry like this:</p>
50 *
51 * <pre><code>
52 * <action path="/saveSubscription"
53 * type="org.example.SubscriptionAction"
54 * name="subscriptionForm"
55 * scope="request"
56 * input="/subscription.jsp"
57 * parameter="save,back,recalc=recalculate,default=save"/>
58 * </code></pre>
59 *
60 * <p>where <code>parameter</code> contains three possible methods and one
61 * default method if nothing matches (such as the user pressing the enter key).</p>
62 *
63 * <p>For utility purposes, you can use the <code>key=value</code> notation to
64 * alias methods so that they are exposed as different form element names, in the
65 * event of a naming conflict or otherwise. In this example, the <em>recalc</em>
66 * button (via a request parameter) will invoke the <code>recalculate</code>
67 * method. The security-minded person may find this feature valuable to
68 * obfuscate and not expose the methods.</p>
69 *
70 * <p>The <em>default</em> key is purely optional. If this is not specified
71 * and no parameters match the list of method keys, <code>null</code> is
72 * returned which means the <code>unspecified</code> method will be invoked.</p>
73 *
74 * <p>The order of the parameters are guaranteed to be iterated in the order
75 * specified. If multiple buttons were accidently submitted, the first match in
76 * the list will be dispatched.</p>
77 *
78 * <p>To implement this <i>dispatch</i> behaviour in an <code>Action</code>,
79 * class create your custom Action as follows, along with the methods you require
80 * (and optionally "cancelled" and "unspecified" methods):</p> <p/>
81 * <pre>
82 * public class MyCustomAction extends Action {
83 *
84 * protected ActionDispatcher dispatcher = new EventActionDispatcher(this);
85 *
86 * public ActionForward execute(ActionMapping mapping,
87 * ActionForm form,
88 * HttpServletRequest request,
89 * HttpServletResponse response)
90 * throws Exception {
91 * return dispatcher.execute(mapping, form, request, response);
92 * }
93 * }
94 * </pre>
95 * <p/>
96 *
97 * @since Struts 1.2.9
98 */
99 public class EventActionDispatcher extends ActionDispatcher {
100
101 /**
102 * Commons Logging instance.
103 */
104 private static final Log LOG = LogFactory.getLog(EventActionDispatcher.class);
105
106 /**
107 * The method key, if present, to use if other specified method keys
108 * do not match a request parameter.
109 */
110 private static final String DEFAULT_METHOD_KEY = "default";
111
112 /**
113 * Constructs a new object for the specified action.
114 * @param action the action
115 */
116 public EventActionDispatcher(Action action) {
117 // N.B. MAPPING_FLAVOR causes the getParameter() method
118 // in ActionDispatcher to throw an exception if the
119 // parameter is missing
120 super(action, ActionDispatcher.MAPPING_FLAVOR);
121 }
122
123 /**
124 * <p>Dispatches to the target class' <code>unspecified</code> method, if
125 * present, otherwise throws a ServletException. Classes utilizing
126 * <code>EventActionDispatcher</code> should provide an <code>unspecified</code>
127 * method if they wish to provide behavior different than throwing a
128 * ServletException.</p>
129 *
130 * @param mapping The ActionMapping used to select this instance
131 * @param form The optional ActionForm bean for this request (if any)
132 * @param request The non-HTTP request we are processing
133 * @param response The non-HTTP response we are creating
134 * @return The forward to which control should be transferred, or
135 * <code>null</code> if the response has been completed.
136 * @throws Exception if the application business logic throws an
137 * exception.
138 */
139 protected ActionForward unspecified(ActionMapping mapping, ActionForm form,
140 HttpServletRequest request, HttpServletResponse response)
141 throws Exception {
142 // Identify if there is an "unspecified" method to be dispatched to
143 String name = "unspecified";
144 Method method = null;
145
146 try {
147 method = getMethod(name);
148 } catch (NoSuchMethodException e) {
149 String message =
150 messages.getMessage("event.parameter", mapping.getPath());
151
152 LOG.error(message + " " + mapping.getParameter());
153
154 throw new ServletException(message);
155 }
156
157 return dispatchMethod(mapping, form, request, response, name, method);
158 }
159
160 /**
161 * Returns the method name, given a parameter's value.
162 *
163 * @param mapping The ActionMapping used to select this instance
164 * @param form The optional ActionForm bean for this request (if
165 * any)
166 * @param request The HTTP request we are processing
167 * @param response The HTTP response we are creating
168 * @param parameter The <code>ActionMapping</code> parameter's name
169 * @return The method's name.
170 * @throws Exception if an error occurs.
171 */
172 protected String getMethodName(ActionMapping mapping, ActionForm form,
173 HttpServletRequest request, HttpServletResponse response,
174 String parameter) throws Exception {
175
176 StringTokenizer st = new StringTokenizer(parameter, ",");
177 String defaultMethodName = null;
178
179 while (st.hasMoreTokens()) {
180 String methodKey = st.nextToken().trim();
181 String methodName = methodKey;
182
183 // The key can either be a direct method name or an alias
184 // to a method as indicated by a "key=value" signature
185 int equals = methodKey.indexOf('=');
186 if (equals > -1) {
187 methodName = methodKey.substring(equals + 1).trim();
188 methodKey = methodKey.substring(0, equals).trim();
189 }
190
191 // Set the default if it passes by
192 if (methodKey.equals(DEFAULT_METHOD_KEY)) {
193 defaultMethodName = methodName;
194 }
195
196 // If the method key exists as a standalone parameter or with
197 // the image suffixes (.x/.y), the method name has been found.
198 if ((request.getParameter(methodKey) != null)
199 || (request.getParameter(methodKey + ".x") != null)) {
200 return methodName;
201 }
202 }
203
204 return defaultMethodName;
205 }
206 }