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 package org.apache.struts.apps.mailreader.plugin;
22
23
24 import org.apache.commons.logging.Log;
25 import org.apache.commons.logging.LogFactory;
26 import org.apache.struts.action.ActionServlet;
27 import org.apache.struts.action.PlugIn;
28 import org.apache.struts.apps.mailreader.Constants;
29 import org.apache.struts.apps.mailreader.dao.impl.memory.MemoryUserDatabase;
30 import org.apache.struts.config.ModuleConfig;
31
32 import javax.servlet.ServletException;
33 import java.io.BufferedInputStream;
34 import java.io.BufferedOutputStream;
35 import java.io.File;
36 import java.io.FileOutputStream;
37 import java.io.InputStream;
38
39 /**
40 * <p><strong>MemoryDatabasePlugIn</strong> initializes and finalizes the
41 * persistent storage of User and Subscription information for the Struts
42 * Demonstration Application, using an in-memory database backed by an
43 * XML file.</p>
44 *
45 * <p><strong>IMPLEMENTATION WARNING</strong> - If this web application is run
46 * from a WAR file, or in another environment where reading and writing of the
47 * web application resource is impossible, the initial contents will be copied
48 * to a file in the web application temporary directory provided by the
49 * container. This is for demonstration purposes only - you should
50 * <strong>NOT</strong> assume that files written here will survive a restart
51 * of your servlet container.</p>
52 *
53 * @version $Rev: 471754 $ $Date: 2006-11-06 08:55:09 -0600 (Mon, 06 Nov 2006) $
54 */
55
56 public final class MemoryDatabasePlugIn implements PlugIn {
57
58 // ---- Instance Variables ----
59
60 /**
61 * The {@link MemoryUserDatabase} object we construct and make available.
62 */
63 private MemoryUserDatabase database = null;
64
65
66 /**
67 * Logging output for this plug in instance.
68 */
69 private Log log = LogFactory.getLog(this.getClass());
70
71
72 /**
73 * The {@link ActionServlet} owning this application.
74 */
75 private ActionServlet servlet = null;
76
77 // ---- Properties ----
78
79 /**
80 * The web application resource path of our persistent database
81 * storage file.
82 */
83 private String pathname = "/WEB-INF/database.xml";
84
85 public String getPathname() {
86 return (this.pathname);
87 }
88
89 public void setPathname(String pathname) {
90 this.pathname = pathname;
91 }
92
93 // ---- PlugIn Methods ----
94
95
96 /**
97 * Gracefully shut down this database, releasing any resources
98 * that were allocated at initialization.
99 */
100 public void destroy() {
101
102 log.info("Finalizing memory database plug in");
103
104 if (database != null) {
105 try {
106 database.close();
107 } catch (Exception e) {
108 log.error("Closing memory database", e);
109 }
110 }
111
112 servlet.getServletContext().removeAttribute(Constants.DATABASE_KEY);
113 database = null;
114 servlet = null;
115 database = null;
116 }
117
118
119 /**
120 * Initialize and load our initial database from persistent storage.
121 *
122 * @param servlet The ActionServlet for this web application
123 * @param config The ApplicationConfig for our owning module
124 * @throws ServletException if we cannot configure ourselves correctly
125 */
126 public void init(ActionServlet servlet, ModuleConfig config)
127 throws ServletException {
128
129 log.info("Initializing memory database plug in from '" +
130 pathname + "'");
131
132 // Remember our associated configuration and servlet
133 this.servlet = servlet;
134
135 // Construct a new database and make it available
136 database = new MemoryUserDatabase();
137 try {
138 String path = calculatePath();
139 if (log.isDebugEnabled()) {
140 log.debug(" Loading database from '" + path + "'");
141 }
142 database.setPathname(path);
143 database.open();
144 } catch (Exception e) {
145 log.error("Opening memory database", e);
146 throw new ServletException("Cannot load database from '" +
147 pathname + "'", e);
148 }
149
150 // Make the initialized database available
151 servlet.getServletContext().setAttribute(Constants.DATABASE_KEY,
152 database);
153
154 }
155
156 // ---- Private Methods ----
157
158 /**
159 * Calculate and return an absolute pathname to the XML file to contain
160 * our persistent storage information.
161 *
162 * @throws Exception if an input/output error occurs
163 */
164 private String calculatePath() throws Exception {
165
166 // Can we access the database via file I/O?
167 String path = servlet.getServletContext().getRealPath(pathname);
168 if (path != null) {
169 return (path);
170 }
171
172 // Does a copy of this file already exist in our temporary directory
173 File dir = (File)
174 servlet.getServletContext().getAttribute
175 ("javax.servlet.context.tempdir");
176 File file = new File(dir, "struts-example-database.xml");
177 if (file.exists()) {
178 return (file.getAbsolutePath());
179 }
180
181 // Copy the static resource to a temporary file and return its path
182 InputStream is =
183 servlet.getServletContext().getResourceAsStream(pathname);
184 BufferedInputStream bis = new BufferedInputStream(is, 1024);
185 FileOutputStream os =
186 new FileOutputStream(file);
187 BufferedOutputStream bos = new BufferedOutputStream(os, 1024);
188 byte buffer[] = new byte[1024];
189 while (true) {
190 int n = bis.read(buffer);
191 if (n <= 0) {
192 break;
193 }
194 bos.write(buffer, 0, n);
195 }
196 bos.close();
197 bis.close();
198 return (file.getAbsolutePath());
199
200 }
201
202 }