1 /*
2 * $Id: MemoryDatabasePlugIn.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
23 package org.apache.struts.webapp.example.memory;
24
25
26 import java.io.BufferedInputStream;
27 import java.io.BufferedOutputStream;
28 import java.io.File;
29 import java.io.FileOutputStream;
30 import java.io.InputStream;
31 import java.util.ArrayList;
32 import javax.servlet.ServletException;
33 import org.apache.commons.logging.Log;
34 import org.apache.commons.logging.LogFactory;
35 import org.apache.struts.action.ActionServlet;
36 import org.apache.struts.action.PlugIn;
37 import org.apache.struts.config.ModuleConfig;
38 import org.apache.struts.util.LabelValueBean;
39 import org.apache.struts.webapp.example.Constants;
40
41 /**
42 * <p><strong>MemoryDatabasePlugIn</strong> initializes and finalizes the
43 * persistent storage of User and Subscription information for the Struts
44 * Demonstration Application, using an in-memory database backed by an
45 * XML file.</p>
46 *
47 * <p><strong>IMPLEMENTATION WARNING</strong> - If this web application is run
48 * from a WAR file, or in another environment where reading and writing of the
49 * web application resource is impossible, the initial contents will be copied
50 * to a file in the web application temporary directory provided by the
51 * container. This is for demonstration purposes only - you should
52 * <strong>NOT</strong> assume that files written here will survive a restart
53 * of your servlet container.</p>
54 *
55 * @author Craig R. McClanahan
56 * @version $Rev: 471754 $ $Date: 2006-11-06 08:55:09 -0600 (Mon, 06 Nov 2006) $
57 */
58
59 public final class MemoryDatabasePlugIn implements PlugIn {
60
61
62 // ----------------------------------------------------- Instance Variables
63
64
65 /**
66 * The {@link MemoryUserDatabase} object we construct and make available.
67 */
68 private MemoryUserDatabase database = null;
69
70
71 /**
72 * Logging output for this plug in instance.
73 */
74 private Log log = LogFactory.getLog(this.getClass());
75
76
77 /**
78 * The {@link ActionServlet} owning this application.
79 */
80 private ActionServlet servlet = null;
81
82
83 // ------------------------------------------------------------- Properties
84
85
86 /**
87 * The web application resource path of our persistent database
88 * storage file.
89 */
90 private String pathname = "/WEB-INF/database.xml";
91
92 public String getPathname() {
93 return (this.pathname);
94 }
95
96 public void setPathname(String pathname) {
97 this.pathname = pathname;
98 }
99
100
101 // --------------------------------------------------------- PlugIn Methods
102
103
104 /**
105 * Gracefully shut down this database, releasing any resources
106 * that were allocated at initialization.
107 */
108 public void destroy() {
109
110 log.info("Finalizing memory database plug in");
111
112 if (database != null) {
113 try {
114 database.close();
115 } catch (Exception e) {
116 log.error("Closing memory database", e);
117 }
118 }
119
120 servlet.getServletContext().removeAttribute(Constants.DATABASE_KEY);
121 database = null;
122 servlet = null;
123 database = null;
124
125 }
126
127
128 /**
129 * Initialize and load our initial database from persistent storage.
130 *
131 * @param servlet The ActionServlet for this web application
132 * @param config The ApplicationConfig for our owning module
133 *
134 * @exception ServletException if we cannot configure ourselves correctly
135 */
136 public void init(ActionServlet servlet, ModuleConfig config)
137 throws ServletException {
138
139 log.info("Initializing memory database plug in from '" +
140 pathname + "'");
141
142 // Remember our associated configuration and servlet
143 this.servlet = servlet;
144
145 // Construct a new database and make it available
146 database = new MemoryUserDatabase();
147 try {
148 String path = calculatePath();
149 if (log.isDebugEnabled()) {
150 log.debug(" Loading database from '" + path + "'");
151 }
152 database.setPathname(path);
153 database.open();
154 } catch (Exception e) {
155 log.error("Opening memory database", e);
156 throw new ServletException("Cannot load database from '" +
157 pathname + "'", e);
158 }
159
160 // Make the initialized database available
161 servlet.getServletContext().setAttribute(Constants.DATABASE_KEY,
162 database);
163
164 // Setup and cache other required data
165 setupCache(servlet, config);
166
167 }
168
169
170 // --------------------------------------------------------- Public Methods
171
172
173 // ------------------------------------------------------ Protected Methods
174
175
176 /**
177 * <p>Cache commonly required data as servlet context attributes.</p>
178 *
179 * @param servlet The <code>ActionServlet</code> instance running
180 * this webapp
181 * @param config The <code>ModuleConfig</code> for this application module
182 */
183 protected void setupCache(ActionServlet servlet, ModuleConfig config) {
184
185 // Set up list of server types under "serverTypes"
186 ArrayList serverTypes = new ArrayList();
187 serverTypes.add(new LabelValueBean("IMAP Protocol", "imap"));
188 serverTypes.add(new LabelValueBean("POP3 Protocol", "pop3"));
189 servlet.getServletContext().setAttribute("serverTypes", serverTypes);
190
191 }
192
193
194
195
196 // -------------------------------------------------------- Private Methods
197
198
199 /**
200 * Calculate and return an absolute pathname to the XML file to contain
201 * our persistent storage information.
202 *
203 * @exception Exception if an input/output error occurs
204 */
205 private String calculatePath() throws Exception {
206
207 // Can we access the database via file I/O?
208 String path = servlet.getServletContext().getRealPath(pathname);
209 if (path != null) {
210 return (path);
211 }
212
213 // Does a copy of this file already exist in our temporary directory
214 File dir = (File)
215 servlet.getServletContext().getAttribute
216 ("javax.servlet.context.tempdir");
217 File file = new File(dir, "struts-example-database.xml");
218 if (file.exists()) {
219 return (file.getAbsolutePath());
220 }
221
222 // Copy the static resource to a temporary file and return its path
223 InputStream is =
224 servlet.getServletContext().getResourceAsStream(pathname);
225 BufferedInputStream bis = new BufferedInputStream(is, 1024);
226 FileOutputStream os =
227 new FileOutputStream(file);
228 BufferedOutputStream bos = new BufferedOutputStream(os, 1024);
229 byte buffer[] = new byte[1024];
230 while (true) {
231 int n = bis.read(buffer);
232 if (n <= 0) {
233 break;
234 }
235 bos.write(buffer, 0, n);
236 }
237 bos.close();
238 bis.close();
239 return (file.getAbsolutePath());
240
241 }
242
243
244 }