1
2
3 /*
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
5 *
6 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
7 *
8 * Portions Copyright Apache Software Foundation.
9 *
10 * The contents of this file are subject to the terms of either the GNU
11 * General Public License Version 2 only ("GPL") or the Common Development
12 * and Distribution License("CDDL") (collectively, the "License"). You
13 * may not use this file except in compliance with the License. You can obtain
14 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
15 * or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
16 * language governing permissions and limitations under the License.
17 *
18 * When distributing the software, include this License Header Notice in each
19 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
20 * Sun designates this particular file as subject to the "Classpath" exception
21 * as provided by Sun in the GPL Version 2 section of the License file that
22 * accompanied this code. If applicable, add the following below the License
23 * Header, with the fields enclosed by brackets [] replaced by your own
24 * identifying information: "Portions Copyrighted [year]
25 * [name of copyright owner]"
26 *
27 * Contributor(s):
28 *
29 * If you wish your version of this file to be governed by only the CDDL or
30 * only the GPL Version 2, indicate your decision by adding "[Contributor]
31 * elects to include this software in this distribution under the [CDDL or GPL
32 * Version 2] license." If you don't indicate a single choice of license, a
33 * recipient has the option to distribute your version of this file under
34 * either the CDDL, the GPL Version 2 or to extend the choice of license to
35 * its licensees as provided above. However, if you add GPL Version 2 code
36 * and therefore, elected the GPL Version 2 license, then the option applies
37 * only if the new code is made subject to such option by the copyright
38 * holder.
39 */
40
41 package javax.servlet;
42
43 import java.io.IOException;
44 import java.util.Enumeration;
45 import java.util.ResourceBundle;
46
47 /**
48 *
49 * Defines a generic, protocol-independent
50 * servlet. To write an HTTP servlet for use on the
51 * Web, extend {@link javax.servlet.http.HttpServlet} instead.
52 *
53 * <p><code>GenericServlet</code> implements the <code>Servlet</code>
54 * and <code>ServletConfig</code> interfaces. <code>GenericServlet</code>
55 * may be directly extended by a servlet, although it's more common to extend
56 * a protocol-specific subclass such as <code>HttpServlet</code>.
57 *
58 * <p><code>GenericServlet</code> makes writing servlets
59 * easier. It provides simple versions of the lifecycle methods
60 * <code>init</code> and <code>destroy</code> and of the methods
61 * in the <code>ServletConfig</code> interface. <code>GenericServlet</code>
62 * also implements the <code>log</code> method, declared in the
63 * <code>ServletContext</code> interface.
64 *
65 * <p>To write a generic servlet, you need only
66 * override the abstract <code>service</code> method.
67 *
68 *
69 * @author Various
70 */
71
72
73 public abstract class GenericServlet
74 implements Servlet, ServletConfig, java.io.Serializable
75 {
76 private static final String LSTRING_FILE = "javax.servlet.LocalStrings";
77 private static ResourceBundle lStrings =
78 ResourceBundle.getBundle(LSTRING_FILE);
79
80 private transient ServletConfig config;
81
82
83 /**
84 *
85 * Does nothing. All of the servlet initialization
86 * is done by one of the <code>init</code> methods.
87 *
88 */
89
90 public GenericServlet() { }
91
92
93
94 /**
95 * Called by the servlet container to indicate to a servlet that the
96 * servlet is being taken out of service. See {@link Servlet#destroy}.
97 *
98 *
99 */
100
101 public void destroy() {
102 }
103
104
105
106 /**
107 * Returns a <code>String</code> containing the value of the named
108 * initialization parameter, or <code>null</code> if the parameter does
109 * not exist. See {@link ServletConfig#getInitParameter}.
110 *
111 * <p>This method is supplied for convenience. It gets the
112 * value of the named parameter from the servlet's
113 * <code>ServletConfig</code> object.
114 *
115 * @param name a <code>String</code> specifying the name
116 * of the initialization parameter
117 *
118 * @return String a <code>String</code> containing the value
119 * of the initialization parameter
120 *
121 */
122
123 public String getInitParameter(String name) {
124 ServletConfig sc = getServletConfig();
125 if (sc == null) {
126 throw new IllegalStateException(
127 lStrings.getString("err.servlet_config_not_initialized"));
128 }
129
130 return sc.getInitParameter(name);
131 }
132
133
134
135 /**
136 * Returns the names of the servlet's initialization parameters
137 * as an <code>Enumeration</code> of <code>String</code> objects,
138 * or an empty <code>Enumeration</code> if the servlet has no
139 * initialization parameters. See {@link
140 * ServletConfig#getInitParameterNames}.
141 *
142 * <p>This method is supplied for convenience. It gets the
143 * parameter names from the servlet's <code>ServletConfig</code> object.
144 *
145 *
146 * @return Enumeration an enumeration of <code>String</code>
147 * objects containing the names of
148 * the servlet's initialization parameters
149 *
150 */
151
152 public Enumeration getInitParameterNames() {
153 ServletConfig sc = getServletConfig();
154 if (sc == null) {
155 throw new IllegalStateException(
156 lStrings.getString("err.servlet_config_not_initialized"));
157 }
158
159 return sc.getInitParameterNames();
160 }
161
162
163
164
165
166 /**
167 * Returns this servlet's {@link ServletConfig} object.
168 *
169 * @return ServletConfig the <code>ServletConfig</code> object
170 * that initialized this servlet
171 *
172 */
173
174 public ServletConfig getServletConfig() {
175 return config;
176 }
177
178
179
180
181 /**
182 * Returns a reference to the {@link ServletContext} in which this servlet
183 * is running. See {@link ServletConfig#getServletContext}.
184 *
185 * <p>This method is supplied for convenience. It gets the
186 * context from the servlet's <code>ServletConfig</code> object.
187 *
188 *
189 * @return ServletContext the <code>ServletContext</code> object
190 * passed to this servlet by the <code>init</code>
191 * method
192 *
193 */
194
195 public ServletContext getServletContext() {
196 ServletConfig sc = getServletConfig();
197 if (sc == null) {
198 throw new IllegalStateException(
199 lStrings.getString("err.servlet_config_not_initialized"));
200 }
201
202 return sc.getServletContext();
203 }
204
205
206
207
208
209 /**
210 * Returns information about the servlet, such as
211 * author, version, and copyright.
212 * By default, this method returns an empty string. Override this method
213 * to have it return a meaningful value. See {@link
214 * Servlet#getServletInfo}.
215 *
216 *
217 * @return String information about this servlet, by default an
218 * empty string
219 *
220 */
221
222 public String getServletInfo() {
223 return "";
224 }
225
226
227
228
229 /**
230 *
231 * Called by the servlet container to indicate to a servlet that the
232 * servlet is being placed into service. See {@link Servlet#init}.
233 *
234 * <p>This implementation stores the {@link ServletConfig}
235 * object it receives from the servlet container for later use.
236 * When overriding this form of the method, call
237 * <code>super.init(config)</code>.
238 *
239 * @param config the <code>ServletConfig</code> object
240 * that contains configutation
241 * information for this servlet
242 *
243 * @exception ServletException if an exception occurs that
244 * interrupts the servlet's normal
245 * operation
246 *
247 *
248 * @see UnavailableException
249 *
250 */
251
252 public void init(ServletConfig config) throws ServletException {
253 this.config = config;
254 this.init();
255 }
256
257
258
259
260
261 /**
262 *
263 * A convenience method which can be overridden so that there's no need
264 * to call <code>super.init(config)</code>.
265 *
266 * <p>Instead of overriding {@link #init(ServletConfig)}, simply override
267 * this method and it will be called by
268 * <code>GenericServlet.init(ServletConfig config)</code>.
269 * The <code>ServletConfig</code> object can still be retrieved via {@link
270 * #getServletConfig}.
271 *
272 * @exception ServletException if an exception occurs that
273 * interrupts the servlet's
274 * normal operation
275 *
276 */
277
278 public void init() throws ServletException {
279
280 }
281
282
283
284
285 /**
286 *
287 * Writes the specified message to a servlet log file, prepended by the
288 * servlet's name. See {@link ServletContext#log(String)}.
289 *
290 * @param msg a <code>String</code> specifying
291 * the message to be written to the log file
292 *
293 */
294
295 public void log(String msg) {
296 getServletContext().log(getServletName() + ": "+ msg);
297 }
298
299
300
301
302 /**
303 * Writes an explanatory message and a stack trace
304 * for a given <code>Throwable</code> exception
305 * to the servlet log file, prepended by the servlet's name.
306 * See {@link ServletContext#log(String, Throwable)}.
307 *
308 *
309 * @param message a <code>String</code> that describes
310 * the error or exception
311 *
312 * @param t the <code>java.lang.Throwable</code> error
313 * or exception
314 *
315 *
316 */
317
318 public void log(String message, Throwable t) {
319 getServletContext().log(getServletName() + ": " + message, t);
320 }
321
322
323
324 /**
325 * Called by the servlet container to allow the servlet to respond to
326 * a request. See {@link Servlet#service}.
327 *
328 * <p>This method is declared abstract so subclasses, such as
329 * <code>HttpServlet</code>, must override it.
330 *
331 *
332 *
333 * @param req the <code>ServletRequest</code> object
334 * that contains the client's request
335 *
336 * @param res the <code>ServletResponse</code> object
337 * that will contain the servlet's response
338 *
339 * @exception ServletException if an exception occurs that
340 * interferes with the servlet's
341 * normal operation occurred
342 *
343 * @exception IOException if an input or output
344 * exception occurs
345 *
346 */
347
348 public abstract void service(ServletRequest req, ServletResponse res)
349 throws ServletException, IOException;
350
351
352
353 /**
354 * Returns the name of this servlet instance.
355 * See {@link ServletConfig#getServletName}.
356 *
357 * @return the name of this servlet instance
358 *
359 *
360 *
361 */
362
363 public String getServletName() {
364 ServletConfig sc = getServletConfig();
365 if (sc == null) {
366 throw new IllegalStateException(
367 lStrings.getString("err.servlet_config_not_initialized"));
368 }
369
370 return sc.getServletName();
371 }
372 }
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