001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *  http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing,
013     * software distributed under the License is distributed on an
014     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015     * KIND, either express or implied.  See the License for the
016     * specific language governing permissions and limitations
017     * under the License.
018     */
019    
020    //
021    // This source code implements specifications defined by the Java
022    // Community Process. In order to remain compliant with the specification
023    // DO NOT add / change / or delete method signatures!
024    //
025    
026    package javax.servlet;
027    
028    import java.io.InputStream;
029    import java.net.MalformedURLException;
030    import java.net.URL;
031    import java.util.Enumeration;
032    import java.util.Set;
033    
034    /**
035     * Defines a set of methods that a servlet uses to communicate with its
036     * servlet container, for example, to get the MIME type of a file, dispatch
037     * requests, or write to a log file.
038     *
039     * <p>There is one context per "web application" per Java Virtual Machine.  (A
040     * "web application" is a collection of servlets and content installed under a
041     * specific subset of the server's URL namespace such as <code>/catalog</code>
042     * and possibly installed via a <code>.war</code> file.)
043     *
044     * <p>In the case of a web
045     * application marked "distributed" in its deployment descriptor, there will
046     * be one context instance for each virtual machine.  In this situation, the
047     * context cannot be used as a location to share global information (because
048     * the information won't be truly global).  Use an external resource like
049     * a database instead.
050     *
051     * <p>The <code>ServletContext</code> object is contained within
052     * the {@link ServletConfig} object, which the Web server provides the
053     * servlet when the servlet is initialized.
054     *
055     * @see Servlet#getServletConfig
056     * @see ServletConfig#getServletContext
057     *
058     * @version $Rev: 467553 $ $Date: 2006-10-25 06:01:51 +0200 (Mi, 25. Okt 2006) $
059     */
060    public interface ServletContext {
061        /**
062         * Returns a <code>ServletContext</code> object that
063         * corresponds to a specified URL on the server.
064         *
065         * <p>This method allows servlets to gain
066         * access to the context for various parts of the server, and as
067         * needed obtain {@link RequestDispatcher} objects from the context.
068         * The given path must be begin with "/", is interpreted relative
069         * to the server's document root and is matched against the context roots of
070         * other web applications hosted on this container.
071         *
072         * <p>In a security conscious environment, the servlet container may
073         * return <code>null</code> for a given URL.
074         *
075         * @param uripath a <code>String</code> specifying the context path of
076         * another web application in the container.
077         * @return the <code>ServletContext</code> object that
078         * corresponds to the named URL, or null if either none exists or the
079         * container wishes to restrict this access.
080         *
081         * @see RequestDispatcher
082         */
083        public ServletContext getContext(String uripath);
084    
085        /**
086         * Returns the major version of the Java Servlet API that this
087         * servlet container supports. All implementations that comply
088         * with Version 2.4 must have this method
089         * return the integer 2.
090         *
091         * @return 2
092         */
093        public int getMajorVersion();
094    
095        /**
096         * Returns the minor version of the Servlet API that this
097         * servlet container supports. All implementations that comply
098         * with Version 2.4 must have this method
099         * return the integer 4.
100         *
101         * @return 4
102         */
103        public int getMinorVersion();
104    
105        /**
106         * Returns the MIME type of the specified file, or <code>null</code> if
107         * the MIME type is not known. The MIME type is determined
108         * by the configuration of the servlet container, and may be specified
109         * in a web application deployment descriptor. Common MIME
110         * types are <code>"text/html"</code> and <code>"image/gif"</code>.
111         *
112         * @param file a <code>String</code> specifying the name
113         * of a file
114         *
115         * @return a <code>String</code> specifying the file's MIME type
116         */
117        public String getMimeType(String file);
118    
119        /**
120         * Returns a directory-like listing of all the paths to resources within
121         * the web application whose longest sub-path matches the supplied path
122         * argument. Paths indicating subdirectory paths end with a '/'. The
123         * returned paths are all relative to the root of the web application and
124         * have a leading '/'. For example, for a web application containing<br>
125         * <br>
126         * /welcome.html<br>
127         * /catalog/index.html<br>
128         * /catalog/products.html<br>
129         * /catalog/offers/books.html<br>
130         * /catalog/offers/music.html<br>
131         * /customer/login.jsp<br>
132         * /WEB-INF/web.xml<br>
133         * /WEB-INF/classes/com.acme.OrderServlet.class,<br><br>
134         *
135         * getResourcePaths("/") returns {"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}<br>
136         * getResourcePaths("/catalog/") returns {"/catalog/index.html", "/catalog/products.html", "/catalog/offers/"}.<br>
137         *
138         * @param path the partial path used to match the resources,
139         *  which must start with a /
140         * @return a Set containing the directory listing, or null if there are no
141         * resources in the web application whose path begins with the supplied path.
142         *
143         * @since Servlet 2.3
144         */
145        public Set getResourcePaths(String path);
146    
147        /**
148         * Returns a URL to the resource that is mapped to a specified
149         * path. The path must begin with a "/" and is interpreted
150         * as relative to the current context root.
151         *
152         * <p>This method allows the servlet container to make a resource
153         * available to servlets from any source. Resources
154         * can be located on a local or remote
155         * file system, in a database, or in a <code>.war</code> file.
156         *
157         * <p>The servlet container must implement the URL handlers
158         * and <code>URLConnection</code> objects that are necessary
159         * to access the resource.
160         *
161         * <p>This method returns <code>null</code>
162         * if no resource is mapped to the pathname.
163         *
164         * <p>Some containers may allow writing to the URL returned by
165         * this method using the methods of the URL class.
166         *
167         * <p>The resource content is returned directly, so be aware that
168         * requesting a <code>.jsp</code> page returns the JSP source code.
169         * Use a <code>RequestDispatcher</code> instead to include results of
170         * an execution.
171         *
172         * <p>This method has a different purpose than
173         * <code>java.lang.Class.getResource</code>,
174         * which looks up resources based on a class loader. This
175         * method does not use class loaders.
176         *
177         * @param path a <code>String</code> specifying the path to the resource
178         *
179         * @return the resource located at the named path, or <code>null</code>
180         * if there is no resource at that path
181         *
182         * @exception MalformedURLException if the pathname is not given in
183         * the correct form
184         */
185        public URL getResource(String path) throws MalformedURLException;
186    
187        /**
188         * Returns the resource located at the named path as
189         * an <code>InputStream</code> object.
190         *
191         * <p>The data in the <code>InputStream</code> can be
192         * of any type or length. The path must be specified according
193         * to the rules given in <code>getResource</code>.
194         * This method returns <code>null</code> if no resource exists at
195         * the specified path.
196         *
197         * <p>Meta-information such as content length and content type
198         * that is available via <code>getResource</code>
199         * method is lost when using this method.
200         *
201         * <p>The servlet container must implement the URL handlers
202         * and <code>URLConnection</code> objects necessary to access
203         * the resource.
204         *
205         * <p>This method is different from
206         * <code>java.lang.Class.getResourceAsStream</code>,
207         * which uses a class loader. This method allows servlet containers
208         * to make a resource available
209         * to a servlet from any location, without using a class loader.
210         *
211         * @param path a <code>String</code> specifying the path
212         * to the resource
213         *
214         * @return the <code>InputStream</code> returned to the
215         * servlet, or <code>null</code> if no resource exists at the
216         * specified path
217         */
218        public InputStream getResourceAsStream(String path);
219    
220        /**
221         * Returns a {@link RequestDispatcher} object that acts
222         * as a wrapper for the resource located at the given path.
223         * A <code>RequestDispatcher</code> object can be used to forward
224         * a request to the resource or to include the resource in a response.
225         * The resource can be dynamic or static.
226         *
227         * <p>The pathname must begin with a "/" and is interpreted as relative
228         * to the current context root.  Use <code>getContext</code> to obtain
229         * a <code>RequestDispatcher</code> for resources in foreign contexts.
230         * This method returns <code>null</code> if the <code>ServletContext</code>
231         * cannot return a <code>RequestDispatcher</code>.
232         *
233         * @param path a <code>String</code> specifying the pathname
234         * to the resource
235         *
236         * @return a <code>RequestDispatcher</code> object that acts as a wrapper
237         * for the resource at the specified path, or <code>null</code> if the
238         * <code>ServletContext</code> cannot return a <code>RequestDispatcher</code>
239         *
240         * @see RequestDispatcher
241         * @see ServletContext#getContext
242         */
243        public RequestDispatcher getRequestDispatcher(String path);
244    
245        /**
246         * Returns a {@link RequestDispatcher} object that acts
247         * as a wrapper for the named servlet.
248         *
249         * <p>Servlets (and JSP pages also) may be given names via server
250         * administration or via a web application deployment descriptor.
251         * A servlet instance can determine its name using
252         * {@link ServletConfig#getServletName}.
253         *
254         * <p>This method returns <code>null</code> if the
255         * <code>ServletContext</code>
256         * cannot return a <code>RequestDispatcher</code> for any reason.
257         *
258         * @param name a <code>String</code> specifying the name
259         * of a servlet to wrap
260         *
261         * @return a <code>RequestDispatcher</code> object
262         * that acts as a wrapper for the named servlet,
263         * or <code>null</code> if the <code>ServletContext</code>
264         * cannot return a <code>RequestDispatcher</code>
265         *
266         * @see RequestDispatcher
267         * @see ServletContext#getContext
268         * @see ServletConfig#getServletName
269         */
270        public RequestDispatcher getNamedDispatcher(String name);
271    
272        /**
273         * @deprecated As of Java Servlet API 2.1, with no direct replacement.
274         *
275         * <p>This method was originally defined to retrieve a servlet
276         * from a <code>ServletContext</code>. In this version, this method
277         * always returns <code>null</code> and remains only to preserve
278         * binary compatibility. This method will be permanently removed
279         * in a future version of the Java Servlet API.
280         *
281         * <p>In lieu of this method, servlets can share information using the
282         * <code>ServletContext</code> class and can perform shared business logic
283         * by invoking methods on common non-servlet classes.
284         */
285        public Servlet getServlet(String name) throws ServletException;
286    
287        /**
288         * @deprecated As of Java Servlet API 2.0, with no replacement.
289         *
290         * <p>This method was originally defined to return an <code>Enumeration</code>
291         * of all the servlets known to this servlet context. In this
292         * version, this method always returns an empty enumeration and
293         * remains only to preserve binary compatibility. This method
294         * will be permanently removed in a future version of the Java
295         * Servlet API.
296         */
297        public Enumeration getServlets();
298    
299        /**
300         * @deprecated As of Java Servlet API 2.1, with no replacement.
301         *
302         * <p>This method was originally defined to return an
303         * <code>Enumeration</code>
304         * of all the servlet names known to this context. In this version,
305         * this method always returns an empty <code>Enumeration</code> and
306         * remains only to preserve binary compatibility. This method will
307         * be permanently removed in a future version of the Java Servlet API.
308         */
309        public Enumeration getServletNames();
310    
311        /**
312         * Writes the specified message to a servlet log file, usually
313         * an event log. The name and type of the servlet log file is
314         * specific to the servlet container.
315         *
316         * @param msg a <code>String</code> specifying the
317         * message to be written to the log file
318         */
319        public void log(String msg);
320    
321        /**
322         * @deprecated As of Java Servlet API 2.1, use
323         * {@link #log(String message, Throwable throwable)}
324         * instead.
325         *
326         * <p>This method was originally defined to write an
327         * exception's stack trace and an explanatory error message
328         * to the servlet log file.
329         */
330        public void log(Exception exception, String msg);
331    
332        /**
333         * Writes an explanatory message and a stack trace
334         * for a given <code>Throwable</code> exception
335         * to the servlet log file. The name and type of the servlet log
336         * file is specific to the servlet container, usually an event log.
337         *
338         * @param message a <code>String</code> that
339         * describes the error or exception
340         *
341         * @param throwable the <code>Throwable</code> error
342         * or exception
343         */
344        public void log(String message, Throwable throwable);
345    
346        /**
347         * Returns a <code>String</code> containing the real path
348         * for a given virtual path. For example, the path "/index.html"
349         * returns the absolute file path on the server's filesystem would be
350         * served by a request for "http://host/contextPath/index.html",
351         * where contextPath is the context path of this ServletContext..
352         *
353         * <p>The real path returned will be in a form
354         * appropriate to the computer and operating system on
355         * which the servlet container is running, including the
356         * proper path separators. This method returns <code>null</code>
357         * if the servlet container cannot translate the virtual path
358         * to a real path for any reason (such as when the content is
359         * being made available from a <code>.war</code> archive).
360         *
361         * @param path a <code>String</code> specifying a virtual path
362         *
363         * @return a <code>String</code> specifying the real path,
364         * or null if the translation cannot be performed
365         */
366        public String getRealPath(String path);
367    
368        /**
369         * Returns the name and version of the servlet container on which
370         * the servlet is running.
371         *
372         * <p>The form of the returned string is
373         * <i>servername</i>/<i>versionnumber</i>.
374         * For example, the JavaServer Web Development Kit may return the string
375         * <code>JavaServer Web Dev Kit/1.0</code>.
376         *
377         * <p>The servlet container may return other optional information
378         * after the primary string in parentheses, for example,
379         * <code>JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86)</code>.
380         *
381         * @return a <code>String</code> containing at least the
382         * servlet container name and version number
383         */
384        public String getServerInfo();
385    
386        /**
387         * Returns a <code>String</code> containing the value of the named
388         * context-wide initialization parameter, or <code>null</code> if the
389         * parameter does not exist.
390         *
391         * <p>This method can make available configuration information useful
392         * to an entire "web application".  For example, it can provide a
393         * webmaster's email address or the name of a system that holds
394         * critical data.
395         *
396         * @param name a <code>String</code> containing the name of the
397         * parameter whose value is requested
398         *
399         * @return a <code>String</code> containing at least the
400         * servlet container name and version number
401         *
402         * @see ServletConfig#getInitParameter
403         */
404        public String getInitParameter(String name);
405    
406        /**
407         * Returns the names of the context's initialization parameters as an
408         * <code>Enumeration</code> of <code>String</code> objects, or an
409         * empty <code>Enumeration</code> if the context has no initialization
410         * parameters.
411         *
412         * @return an <code>Enumeration</code> of <code>String</code>
413         * objects containing the names of the context's initialization parameters
414         *
415         * @see ServletConfig#getInitParameter
416         */
417        public Enumeration getInitParameterNames();
418    
419    
420        /**
421         * Returns the servlet container attribute with the given name,
422         * or <code>null</code> if there is no attribute by that name.
423         * An attribute allows a servlet container to give the
424         * servlet additional information not
425         * already provided by this interface. See your
426         * server documentation for information about its attributes.
427         * A list of supported attributes can be retrieved using
428         * <code>getAttributeNames</code>.
429         *
430         * <p>The attribute is returned as a <code>java.lang.Object</code>
431         * or some subclass.
432         * Attribute names should follow the same convention as package
433         * names. The Java Servlet API specification reserves names
434         * matching <code>java.*</code>, <code>javax.*</code>,
435         * and <code>sun.*</code>.
436         *
437         * @param name a <code>String</code> specifying the name
438         * of the attribute
439         *
440         * @return an <code>Object</code> containing the value
441         * of the attribute, or <code>null</code> if no attribute
442         * exists matching the given name
443         *
444         * @see ServletContext#getAttributeNames
445         */
446        public Object getAttribute(String name);
447    
448        /**
449         * Returns an <code>Enumeration</code> containing the
450         * attribute names available
451         * within this servlet context. Use the
452         * {@link #getAttribute} method with an attribute name
453         * to get the value of an attribute.
454         *
455         * @return an <code>Enumeration</code> of attribute names
456         *
457         * @see #getAttribute
458         */
459        public Enumeration getAttributeNames();
460    
461        /**
462         * Binds an object to a given attribute name in this servlet context. If
463         * the name specified is already used for an attribute, this
464         * method will replace the attribute with the new to the new attribute.
465         * <p>If listeners are configured on the <code>ServletContext</code> the
466         * container notifies them accordingly.
467         * <p>
468         * If a null value is passed, the effect is the same as calling
469         * <code>removeAttribute()</code>.
470         *
471         * <p>Attribute names should follow the same convention as package
472         * names. The Java Servlet API specification reserves names
473         * matching <code>java.*</code>, <code>javax.*</code>, and
474         * <code>sun.*</code>.
475         *
476         * @param name a <code>String</code> specifying the name
477         * of the attribute
478         *
479         * @param object an <code>Object</code> representing the
480         * attribute to be bound
481         */
482        public void setAttribute(String name, Object object);
483    
484        /**
485         * Removes the attribute with the given name from
486         * the servlet context. After removal, subsequent calls to
487         * {@link #getAttribute} to retrieve the attribute's value
488         * will return <code>null</code>.
489         *
490         * <p>If listeners are configured on the <code>ServletContext</code> the
491         * container notifies them accordingly.
492         *
493         * @param name a <code>String</code> specifying the name
494         * of the attribute to be removed
495         */
496        public void removeAttribute(String name);
497    
498        /**
499         * Returns the name of this web application correponding to this ServletContext as specified in the deployment
500         * descriptor for this web application by the display-name element.
501         *
502         * @return The name of the web application or null if no name has been declared in the deployment descriptor.
503         * @since Servlet 2.3
504         */
505        public String getServletContextName();
506    }