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 }