1 /**
2 *
3 * Copyright 2003-2004 The Apache Software Foundation
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * 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
18
19
20
21
22
23
24 package javax.servlet;
25
26 import java.io.InputStream;
27 import java.net.MalformedURLException;
28 import java.net.URL;
29 import java.util.Enumeration;
30 import java.util.Set;
31
32 /**
33 * Defines a set of methods that a servlet uses to communicate with its
34 * servlet container, for example, to get the MIME type of a file, dispatch
35 * requests, or write to a log file.
36 *
37 * <p>There is one context per "web application" per Java Virtual Machine. (A
38 * "web application" is a collection of servlets and content installed under a
39 * specific subset of the server's URL namespace such as <code>/catalog</code>
40 * and possibly installed via a <code>.war</code> file.)
41 *
42 * <p>In the case of a web
43 * application marked "distributed" in its deployment descriptor, there will
44 * be one context instance for each virtual machine. In this situation, the
45 * context cannot be used as a location to share global information (because
46 * the information won't be truly global). Use an external resource like
47 * a database instead.
48 *
49 * <p>The <code>ServletContext</code> object is contained within
50 * the {@link ServletConfig} object, which the Web server provides the
51 * servlet when the servlet is initialized.
52 *
53 * @see Servlet#getServletConfig
54 * @see ServletConfig#getServletContext
55 *
56 * @version $Rev: 46019 $ $Date: 2004-09-14 02:56:06 -0700 (Tue, 14 Sep 2004) $
57 */
58 public interface ServletContext {
59 /**
60 * Returns a <code>ServletContext</code> object that
61 * corresponds to a specified URL on the server.
62 *
63 * <p>This method allows servlets to gain
64 * access to the context for various parts of the server, and as
65 * needed obtain {@link RequestDispatcher} objects from the context.
66 * The given path must be begin with "/", is interpreted relative
67 * to the server's document root and is matched against the context roots of
68 * other web applications hosted on this container.
69 *
70 * <p>In a security conscious environment, the servlet container may
71 * return <code>null</code> for a given URL.
72 *
73 * @param uripath a <code>String</code> specifying the context path of
74 * another web application in the container.
75 * @return the <code>ServletContext</code> object that
76 * corresponds to the named URL, or null if either none exists or the
77 * container wishes to restrict this access.
78 *
79 * @see RequestDispatcher
80 */
81 public ServletContext getContext(String uripath);
82
83 /**
84 * Returns the major version of the Java Servlet API that this
85 * servlet container supports. All implementations that comply
86 * with Version 2.4 must have this method
87 * return the integer 2.
88 *
89 * @return 2
90 */
91 public int getMajorVersion();
92
93 /**
94 * Returns the minor version of the Servlet API that this
95 * servlet container supports. All implementations that comply
96 * with Version 2.4 must have this method
97 * return the integer 4.
98 *
99 * @return 4
100 */
101 public int getMinorVersion();
102
103 /**
104 * Returns the MIME type of the specified file, or <code>null</code> if
105 * the MIME type is not known. The MIME type is determined
106 * by the configuration of the servlet container, and may be specified
107 * in a web application deployment descriptor. Common MIME
108 * types are <code>"text/html"</code> and <code>"image/gif"</code>.
109 *
110 * @param file a <code>String</code> specifying the name
111 * of a file
112 *
113 * @return a <code>String</code> specifying the file's MIME type
114 */
115 public String getMimeType(String file);
116
117 /**
118 * Returns a directory-like listing of all the paths to resources within
119 * the web application whose longest sub-path matches the supplied path
120 * argument. Paths indicating subdirectory paths end with a '/'. The
121 * returned paths are all relative to the root of the web application and
122 * have a leading '/'. For example, for a web application containing<br>
123 * <br>
124 * /welcome.html<br>
125 * /catalog/index.html<br>
126 * /catalog/products.html<br>
127 * /catalog/offers/books.html<br>
128 * /catalog/offers/music.html<br>
129 * /customer/login.jsp<br>
130 * /WEB-INF/web.xml<br>
131 * /WEB-INF/classes/com.acme.OrderServlet.class,<br><br>
132 *
133 * getResourcePaths("/") returns {"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}<br>
134 * getResourcePaths("/catalog/") returns {"/catalog/index.html", "/catalog/products.html", "/catalog/offers/"}.<br>
135 *
136 * @param path the partial path used to match the resources,
137 * which must start with a /
138 * @return a Set containing the directory listing, or null if there are no
139 * resources in the web application whose path begins with the supplied path.
140 *
141 * @since Servlet 2.3
142 */
143 public Set getResourcePaths(String path);
144
145 /**
146 * Returns a URL to the resource that is mapped to a specified
147 * path. The path must begin with a "/" and is interpreted
148 * as relative to the current context root.
149 *
150 * <p>This method allows the servlet container to make a resource
151 * available to servlets from any source. Resources
152 * can be located on a local or remote
153 * file system, in a database, or in a <code>.war</code> file.
154 *
155 * <p>The servlet container must implement the URL handlers
156 * and <code>URLConnection</code> objects that are necessary
157 * to access the resource.
158 *
159 * <p>This method returns <code>null</code>
160 * if no resource is mapped to the pathname.
161 *
162 * <p>Some containers may allow writing to the URL returned by
163 * this method using the methods of the URL class.
164 *
165 * <p>The resource content is returned directly, so be aware that
166 * requesting a <code>.jsp</code> page returns the JSP source code.
167 * Use a <code>RequestDispatcher</code> instead to include results of
168 * an execution.
169 *
170 * <p>This method has a different purpose than
171 * <code>java.lang.Class.getResource</code>,
172 * which looks up resources based on a class loader. This
173 * method does not use class loaders.
174 *
175 * @param path a <code>String</code> specifying the path to the resource
176 *
177 * @return the resource located at the named path, or <code>null</code>
178 * if there is no resource at that path
179 *
180 * @exception MalformedURLException if the pathname is not given in
181 * the correct form
182 */
183 public URL getResource(String path) throws MalformedURLException;
184
185 /**
186 * Returns the resource located at the named path as
187 * an <code>InputStream</code> object.
188 *
189 * <p>The data in the <code>InputStream</code> can be
190 * of any type or length. The path must be specified according
191 * to the rules given in <code>getResource</code>.
192 * This method returns <code>null</code> if no resource exists at
193 * the specified path.
194 *
195 * <p>Meta-information such as content length and content type
196 * that is available via <code>getResource</code>
197 * method is lost when using this method.
198 *
199 * <p>The servlet container must implement the URL handlers
200 * and <code>URLConnection</code> objects necessary to access
201 * the resource.
202 *
203 * <p>This method is different from
204 * <code>java.lang.Class.getResourceAsStream</code>,
205 * which uses a class loader. This method allows servlet containers
206 * to make a resource available
207 * to a servlet from any location, without using a class loader.
208 *
209 * @param path a <code>String</code> specifying the path
210 * to the resource
211 *
212 * @return the <code>InputStream</code> returned to the
213 * servlet, or <code>null</code> if no resource exists at the
214 * specified path
215 */
216 public InputStream getResourceAsStream(String path);
217
218 /**
219 * Returns a {@link RequestDispatcher} object that acts
220 * as a wrapper for the resource located at the given path.
221 * A <code>RequestDispatcher</code> object can be used to forward
222 * a request to the resource or to include the resource in a response.
223 * The resource can be dynamic or static.
224 *
225 * <p>The pathname must begin with a "/" and is interpreted as relative
226 * to the current context root. Use <code>getContext</code> to obtain
227 * a <code>RequestDispatcher</code> for resources in foreign contexts.
228 * This method returns <code>null</code> if the <code>ServletContext</code>
229 * cannot return a <code>RequestDispatcher</code>.
230 *
231 * @param path a <code>String</code> specifying the pathname
232 * to the resource
233 *
234 * @return a <code>RequestDispatcher</code> object that acts as a wrapper
235 * for the resource at the specified path, or <code>null</code> if the
236 * <code>ServletContext</code> cannot return a <code>RequestDispatcher</code>
237 *
238 * @see RequestDispatcher
239 * @see ServletContext#getContext
240 */
241 public RequestDispatcher getRequestDispatcher(String path);
242
243 /**
244 * Returns a {@link RequestDispatcher} object that acts
245 * as a wrapper for the named servlet.
246 *
247 * <p>Servlets (and JSP pages also) may be given names via server
248 * administration or via a web application deployment descriptor.
249 * A servlet instance can determine its name using
250 * {@link ServletConfig#getServletName}.
251 *
252 * <p>This method returns <code>null</code> if the
253 * <code>ServletContext</code>
254 * cannot return a <code>RequestDispatcher</code> for any reason.
255 *
256 * @param name a <code>String</code> specifying the name
257 * of a servlet to wrap
258 *
259 * @return a <code>RequestDispatcher</code> object
260 * that acts as a wrapper for the named servlet,
261 * or <code>null</code> if the <code>ServletContext</code>
262 * cannot return a <code>RequestDispatcher</code>
263 *
264 * @see RequestDispatcher
265 * @see ServletContext#getContext
266 * @see ServletConfig#getServletName
267 */
268 public RequestDispatcher getNamedDispatcher(String name);
269
270 /**
271 * @deprecated As of Java Servlet API 2.1, with no direct replacement.
272 *
273 * <p>This method was originally defined to retrieve a servlet
274 * from a <code>ServletContext</code>. In this version, this method
275 * always returns <code>null</code> and remains only to preserve
276 * binary compatibility. This method will be permanently removed
277 * in a future version of the Java Servlet API.
278 *
279 * <p>In lieu of this method, servlets can share information using the
280 * <code>ServletContext</code> class and can perform shared business logic
281 * by invoking methods on common non-servlet classes.
282 */
283 public Servlet getServlet(String name) throws ServletException;
284
285 /**
286 * @deprecated As of Java Servlet API 2.0, with no replacement.
287 *
288 * <p>This method was originally defined to return an <code>Enumeration</code>
289 * of all the servlets known to this servlet context. In this
290 * version, this method always returns an empty enumeration and
291 * remains only to preserve binary compatibility. This method
292 * will be permanently removed in a future version of the Java
293 * Servlet API.
294 */
295 public Enumeration getServlets();
296
297 /**
298 * @deprecated As of Java Servlet API 2.1, with no replacement.
299 *
300 * <p>This method was originally defined to return an
301 * <code>Enumeration</code>
302 * of all the servlet names known to this context. In this version,
303 * this method always returns an empty <code>Enumeration</code> and
304 * remains only to preserve binary compatibility. This method will
305 * be permanently removed in a future version of the Java Servlet API.
306 */
307 public Enumeration getServletNames();
308
309 /**
310 * Writes the specified message to a servlet log file, usually
311 * an event log. The name and type of the servlet log file is
312 * specific to the servlet container.
313 *
314 * @param msg a <code>String</code> specifying the
315 * message to be written to the log file
316 */
317 public void log(String msg);
318
319 /**
320 * @deprecated As of Java Servlet API 2.1, use
321 * {@link #log(String message, Throwable throwable)}
322 * instead.
323 *
324 * <p>This method was originally defined to write an
325 * exception's stack trace and an explanatory error message
326 * to the servlet log file.
327 */
328 public void log(Exception exception, String msg);
329
330 /**
331 * Writes an explanatory message and a stack trace
332 * for a given <code>Throwable</code> exception
333 * to the servlet log file. The name and type of the servlet log
334 * file is specific to the servlet container, usually an event log.
335 *
336 * @param message a <code>String</code> that
337 * describes the error or exception
338 *
339 * @param throwable the <code>Throwable</code> error
340 * or exception
341 */
342 public void log(String message, Throwable throwable);
343
344 /**
345 * Returns a <code>String</code> containing the real path
346 * for a given virtual path. For example, the path "/index.html"
347 * returns the absolute file path on the server's filesystem would be
348 * served by a request for "http://host/contextPath/index.html",
349 * where contextPath is the context path of this ServletContext..
350 *
351 * <p>The real path returned will be in a form
352 * appropriate to the computer and operating system on
353 * which the servlet container is running, including the
354 * proper path separators. This method returns <code>null</code>
355 * if the servlet container cannot translate the virtual path
356 * to a real path for any reason (such as when the content is
357 * being made available from a <code>.war</code> archive).
358 *
359 * @param path a <code>String</code> specifying a virtual path
360 *
361 * @return a <code>String</code> specifying the real path,
362 * or null if the translation cannot be performed
363 */
364 public String getRealPath(String path);
365
366 /**
367 * Returns the name and version of the servlet container on which
368 * the servlet is running.
369 *
370 * <p>The form of the returned string is
371 * <i>servername</i>/<i>versionnumber</i>.
372 * For example, the JavaServer Web Development Kit may return the string
373 * <code>JavaServer Web Dev Kit/1.0</code>.
374 *
375 * <p>The servlet container may return other optional information
376 * after the primary string in parentheses, for example,
377 * <code>JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86)</code>.
378 *
379 * @return a <code>String</code> containing at least the
380 * servlet container name and version number
381 */
382 public String getServerInfo();
383
384 /**
385 * Returns a <code>String</code> containing the value of the named
386 * context-wide initialization parameter, or <code>null</code> if the
387 * parameter does not exist.
388 *
389 * <p>This method can make available configuration information useful
390 * to an entire "web application". For example, it can provide a
391 * webmaster's email address or the name of a system that holds
392 * critical data.
393 *
394 * @param name a <code>String</code> containing the name of the
395 * parameter whose value is requested
396 *
397 * @return a <code>String</code> containing at least the
398 * servlet container name and version number
399 *
400 * @see ServletConfig#getInitParameter
401 */
402 public String getInitParameter(String name);
403
404 /**
405 * Returns the names of the context's initialization parameters as an
406 * <code>Enumeration</code> of <code>String</code> objects, or an
407 * empty <code>Enumeration</code> if the context has no initialization
408 * parameters.
409 *
410 * @return an <code>Enumeration</code> of <code>String</code>
411 * objects containing the names of the context's initialization parameters
412 *
413 * @see ServletConfig#getInitParameter
414 */
415 public Enumeration getInitParameterNames();
416
417
418 /**
419 * Returns the servlet container attribute with the given name,
420 * or <code>null</code> if there is no attribute by that name.
421 * An attribute allows a servlet container to give the
422 * servlet additional information not
423 * already provided by this interface. See your
424 * server documentation for information about its attributes.
425 * A list of supported attributes can be retrieved using
426 * <code>getAttributeNames</code>.
427 *
428 * <p>The attribute is returned as a <code>java.lang.Object</code>
429 * or some subclass.
430 * Attribute names should follow the same convention as package
431 * names. The Java Servlet API specification reserves names
432 * matching <code>java.*</code>, <code>javax.*</code>,
433 * and <code>sun.*</code>.
434 *
435 * @param name a <code>String</code> specifying the name
436 * of the attribute
437 *
438 * @return an <code>Object</code> containing the value
439 * of the attribute, or <code>null</code> if no attribute
440 * exists matching the given name
441 *
442 * @see ServletContext#getAttributeNames
443 */
444 public Object getAttribute(String name);
445
446 /**
447 * Returns an <code>Enumeration</code> containing the
448 * attribute names available
449 * within this servlet context. Use the
450 * {@link #getAttribute} method with an attribute name
451 * to get the value of an attribute.
452 *
453 * @return an <code>Enumeration</code> of attribute names
454 *
455 * @see #getAttribute
456 */
457 public Enumeration getAttributeNames();
458
459 /**
460 * Binds an object to a given attribute name in this servlet context. If
461 * the name specified is already used for an attribute, this
462 * method will replace the attribute with the new to the new attribute.
463 * <p>If listeners are configured on the <code>ServletContext</code> the
464 * container notifies them accordingly.
465 * <p>
466 * If a null value is passed, the effect is the same as calling
467 * <code>removeAttribute()</code>.
468 *
469 * <p>Attribute names should follow the same convention as package
470 * names. The Java Servlet API specification reserves names
471 * matching <code>java.*</code>, <code>javax.*</code>, and
472 * <code>sun.*</code>.
473 *
474 * @param name a <code>String</code> specifying the name
475 * of the attribute
476 *
477 * @param object an <code>Object</code> representing the
478 * attribute to be bound
479 */
480 public void setAttribute(String name, Object object);
481
482 /**
483 * Removes the attribute with the given name from
484 * the servlet context. After removal, subsequent calls to
485 * {@link #getAttribute} to retrieve the attribute's value
486 * will return <code>null</code>.
487 *
488 * <p>If listeners are configured on the <code>ServletContext</code> the
489 * container notifies them accordingly.
490 *
491 * @param name a <code>String</code> specifying the name
492 * of the attribute to be removed
493 */
494 public void removeAttribute(String name);
495
496 /**
497 * Returns the name of this web application correponding to this ServletContext as specified in the deployment
498 * descriptor for this web application by the display-name element.
499 *
500 * @return The name of the web application or null if no name has been declared in the deployment descriptor.
501 * @since Servlet 2.3
502 */
503 public String getServletContextName();
504 }