1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.chain.web.servlet;
18
19
20 import java.io.IOException;
21 import javax.servlet.ServletException;
22 import javax.servlet.http.HttpServletRequest;
23 import javax.servlet.http.HttpServletResponse;
24 import org.apache.commons.chain.Catalog;
25 import org.apache.commons.chain.CatalogFactory;
26 import org.apache.commons.chain.Command;
27 import org.apache.commons.chain.web.ChainServlet;
28
29
30 /**
31 * <p>Custom subclass of {@link ChainServlet} that also dispatches incoming
32 * requests to a configurable {@link Command} loaded from the specified
33 * {@link Catalog}.</p>
34 *
35 * <p>In addition to the <em>servlet</em> init parameters supported by
36 * {@link ChainServlet}, this class supports the following additional
37 * parameters:</p>
38 * <ul>
39 * <li><strong>org.apache.commons.chain.CATALOG</strong> - Name of the
40 * catalog from which to acquire commands to be executed. If not
41 * specified, the default catalog for this application will be used.</li>
42 * <li><strong>org.apache.commons.chain.COMMAND</strong> - Name of the
43 * {@link Command} (looked up in our configured {@link Catalog} used
44 * to process all incoming servlet requests. If not specified,
45 * defaults to <code>command</code>.</li>
46 * </ul>
47 *
48 * <p>Also, the <code>org.apache.commons.chain.CONFIG_ATTR</code>
49 * init parameter is also used to identify the
50 * {@link org.apache.commons.chain.Context} attribute under
51 * which our configured {@link Catalog} will be made available to
52 * {@link Command}s processing our requests, in addition to its definition
53 * of the <code>ServletContext</code> attribute key under which the
54 * {@link Catalog} is available.</p>
55 */
56
57 public class ChainProcessor extends ChainServlet {
58
59
60 // ------------------------------------------------------ Manifest Constants
61
62
63 /**
64 * <p>The name of the servlet init parameter containing the name of the
65 * {@link Catalog} to use for processing incoming requests.</p>
66 */
67 public static final String CATALOG =
68 "org.apache.commons.chain.CATALOG";
69
70
71 /**
72 * <p>The default request attribute under which we expose the
73 * {@link Catalog} being used to subordinate {@link Command}s.</p>
74 */
75 public static final String CATALOG_DEFAULT =
76 "org.apache.commons.chain.CATALOG";
77
78
79 /**
80 * <p>The name of the servlet init parameter containing the name of the
81 * {@link Command} (loaded from our configured {@link Catalog} to use
82 * for processing each incoming request.</p>
83 */
84 public static final String COMMAND =
85 "org.apache.commons.chain.COMMAND";
86
87
88 /**
89 * <p>The default command name.</p>
90 */
91 private static final String COMMAND_DEFAULT = "command";
92
93
94 // ------------------------------------------------------ Instance Variables
95
96
97 /**
98 * <p>The name of the context attribute under which our {@link Catalog}
99 * is stored. This value is also used as the name of the
100 * context attribute under which the catalog is exposed to commands.
101 * If not specified, we will look up commands in the appropriate
102 * {@link Catalog} retrieved from our {@link CatalogFactory}.</p>
103 */
104 private String attribute = null;
105
106
107 /**
108 * <p>The name of the {@link Catalog} to retrieve from the
109 * {@link CatalogFactory} for this application, or <code>null</code>
110 * to select the default {@link Catalog}.</p>
111 */
112 private String catalog = null;
113
114
115 /**
116 * <p>The name of the {@link Command} to be executed for each incoming
117 * request.</p>
118 */
119 private String command = null;
120
121
122 // --------------------------------------------------------- Servlet Methods
123
124
125 /**
126 * <p>Clean up as this application is shut down.</p>
127 */
128 public void destroy() {
129
130 super.destroy();
131 attribute = null;
132 catalog = null;
133 command = null;
134
135 }
136
137
138 /**
139 * <p>Cache the name of the command we should execute for each request.</p>
140 *
141 * @exception ServletException if an initialization error occurs
142 */
143 public void init() throws ServletException {
144
145 super.init();
146 attribute = getServletConfig().getInitParameter(CONFIG_ATTR);
147 catalog = getServletConfig().getInitParameter(CATALOG);
148 command = getServletConfig().getInitParameter(COMMAND);
149 if (command == null) {
150 command = COMMAND_DEFAULT;
151 }
152
153 }
154
155
156 /**
157 * <p>Configure a {@link ServletWebContext} for the current request, and
158 * pass it to the <code>execute()</code> method of the specified
159 * {@link Command}, loaded from our configured {@link Catalog}.</p>
160 *
161 * @param request The request we are processing
162 * @param response The response we are creating
163 *
164 * @exception IOException if an input/output error occurs
165 * @exception ServletException if a servlet exception occurs
166 */
167 public void service(HttpServletRequest request,
168 HttpServletResponse response)
169 throws IOException, ServletException {
170
171 ServletWebContext context =
172 new ServletWebContext(getServletContext(), request, response);
173 Catalog theCatalog = null;
174 if (attribute != null) {
175 theCatalog = (Catalog) getServletContext().getAttribute
176 (this.attribute);
177 } else if (catalog != null) {
178 theCatalog = CatalogFactory.getInstance().getCatalog(catalog);
179 } else {
180 theCatalog = CatalogFactory.getInstance().getCatalog();
181 }
182 if (attribute == null) {
183 request.setAttribute(CATALOG_DEFAULT, theCatalog);
184 }
185 Command command = theCatalog.getCommand(this.command);
186 try {
187 command.execute(context);
188 } catch (Exception e) {
189 throw new ServletException(e);
190 }
191
192 }
193
194
195 }