001 /**
002 *
003 * Copyright 2003-2004 The Apache Software Foundation
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 //
019 // This source code implements specifications defined by the Java
020 // Community Process. In order to remain compliant with the specification
021 // DO NOT add / change / or delete method signatures!
022 //
023
024 package javax.servlet;
025
026 import java.io.IOException;
027 import java.io.PrintWriter;
028 import java.util.Locale;
029
030
031 /**
032 * Defines an object to assist a servlet in sending a response to the client.
033 * The servlet container creates a <code>ServletResponse</code> object and
034 * passes it as an argument to the servlet's <code>service</code> method.
035 *
036 * <p>To send binary data in a MIME body response, use
037 * the {@link ServletOutputStream} returned by {@link #getOutputStream}.
038 * To send character data, use the <code>PrintWriter</code> object
039 * returned by {@link #getWriter}. To mix binary and text data,
040 * for example, to create a multipart response, use a
041 * <code>ServletOutputStream</code> and manage the character sections
042 * manually.
043 *
044 * <p>The charset for the MIME body response can be specified
045 * explicitly using the {@link #setCharacterEncoding} and
046 * {@link #setContentType} methods, or implicitly
047 * using the {@link #setLocale} method.
048 * Explicit specifications take precedence over
049 * implicit specifications. If no charset is specified, ISO-8859-1 will be
050 * used. The <code>setCharacterEncoding</code>,
051 * <code>setContentType</code>, or <code>setLocale</code> method must
052 * be called before <code>getWriter</code> and before committing
053 * the response for the character encoding to be used.
054 *
055 * <p>See the Internet RFCs such as
056 * <a href="http://www.ietf.org/rfc/rfc2045.txt">
057 * RFC 2045</a> for more information on MIME. Protocols such as SMTP
058 * and HTTP define profiles of MIME, and those standards
059 * are still evolving.
060 *
061 * @see ServletOutputStream
062 *
063 * @version $Rev: 46019 $ $Date: 2004-09-14 02:56:06 -0700 (Tue, 14 Sep 2004) $
064 */
065 public interface ServletResponse {
066 /**
067 * Returns the name of the character encoding (MIME charset)
068 * used for the body sent in this response.
069 * The character encoding may have been specified explicitly
070 * using the {@link #setCharacterEncoding} or
071 * {@link #setContentType} methods, or implicitly using the
072 * {@link #setLocale} method. Explicit specifications take
073 * precedence over implicit specifications. Calls made
074 * to these methods after <code>getWriter</code> has been
075 * called or after the response has been committed have no
076 * effect on the character encoding. If no character encoding
077 * has been specified, <code>ISO-8859-1</code> is returned.
078 * <p>See RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt)
079 * for more information about character encoding and MIME.
080 *
081 * @return a <code>String</code> specifying the
082 * name of the character encoding, for example, <code>UTF-8</code>
083 */
084 public String getCharacterEncoding();
085
086 /**
087 * Returns the content type used for the MIME body
088 * sent in this response. The content type proper must
089 * have been specified using {@link #setContentType}
090 * before the response is committed. If no content type
091 * has been specified, this method returns null.
092 * If a content type has been specified and a
093 * character encoding has been explicitly or implicitly
094 * specified as described in {@link #getCharacterEncoding},
095 * the charset parameter is included in the string returned.
096 * If no character encoding has been specified, the
097 * charset parameter is omitted.
098 *
099 * @return a <code>String</code> specifying the
100 *
101 * content type, for example, <code>text/html; charset=UTF-8</code>,
102 * or null
103 *
104 * @since Servlet 2.4
105 */
106 public String getContentType();
107
108 /**
109 * Returns a {@link ServletOutputStream} suitable for writing binary
110 * data in the response. The servlet container does not encode the
111 * binary data.
112 *
113 * <p> Calling flush() on the ServletOutputStream commits the response.
114 *
115 * Either this method or {@link #getWriter} may
116 * be called to write the body, not both.
117 *
118 * @return a {@link ServletOutputStream} for writing binary data
119 *
120 * @exception IllegalStateException if the <code>getWriter</code> method
121 * has been called on this response
122 *
123 * @exception IOException if an input or output exception occurred
124 *
125 * @see #getWriter
126 */
127 public ServletOutputStream getOutputStream() throws IOException;
128
129 /**
130 * Returns a <code>PrintWriter</code> object that
131 * can send character text to the client.
132 * The <code>PrintWriter</code> uses the character
133 * encoding returned by {@link #getCharacterEncoding}.
134 * If the response's character encoding has not been
135 * specified as described in <code>getCharacterEncoding</code>
136 * (i.e., the method just returns the default value
137 * <code>ISO-8859-1</code>), <code>getWriter</code>
138 * updates it to <code>ISO-8859-1</code>.
139 * <p>Calling flush() on the <code>PrintWriter</code>
140 * commits the response.
141 * <p>Either this method or {@link #getOutputStream} may be called
142 * to write the body, not both.
143 *
144 * @return a <code>PrintWriter</code> object that
145 * can return character data to the client
146 *
147 * @exception UnsupportedEncodingException if the character encoding
148 * returned by <code>getCharacterEncoding</code> cannot be used
149 *
150 * @exception IllegalStateException if the <code>getOutputStream</code>
151 * method has already been called for this response object
152 *
153 * @exception IOException if an input or output exception occurred
154 *
155 * @see #getOutputStream
156 * @see #setCharacterEncoding
157 */
158 public PrintWriter getWriter() throws IOException;
159
160
161 /**
162 * Sets the character encoding (MIME charset) of the response
163 * being sent to the client, for example, to UTF-8.
164 * If the character encoding has already been set by
165 * {@link #setContentType} or {@link #setLocale},
166 * this method overrides it.
167 * Calling {@link #setContentType} with the <code>String</code>
168 * of <code>text/html</code> and calling
169 * this method with the <code>String</code> of <code>UTF-8</code>
170 * is equivalent with calling
171 * <code>setContentType</code> with the <code>String</code> of
172 * <code>text/html; charset=UTF-8</code>.
173 * <p>This method can be called repeatedly to change the character
174 * encoding.
175 * This method has no effect if it is called after
176 * <code>getWriter</code> has been
177 * called or after the response has been committed.
178 * <p>Containers must communicate the character encoding used for
179 * the servlet response's writer to the client if the protocol
180 * provides a way for doing so. In the case of HTTP, the character
181 * encoding is communicated as part of the <code>Content-Type</code>
182 * header for text media types. Note that the character encoding
183 * cannot be communicated via HTTP headers if the servlet does not
184 * specify a content type; however, it is still used to encode text
185 * written via the servlet response's writer.
186 *
187 * @param charset a String specifying only the character set
188 * defined by IANA Character Sets
189 * (http://www.iana.org/assignments/character-sets)
190 *
191 * @see #setContentType
192 * @see #setLocale
193 *
194 * @since Servlet 2.4
195 */
196 public void setCharacterEncoding(String charset);
197
198 /**
199 * Sets the length of the content body in the response
200 * In HTTP servlets, this method sets the HTTP Content-Length header.
201 *
202 * @param len an integer specifying the length of the
203 * content being returned to the client; sets
204 * the Content-Length header
205 */
206 public void setContentLength(int len);
207
208 /**
209 * Sets the content type of the response being sent to
210 * the client, if the response has not been committed yet.
211 * The given content type may include a character encoding
212 * specification, for example, <code>text/html;charset=UTF-8</code>.
213 * The response's character encoding is only set from the given
214 * content type if this method is called before <code>getWriter</code>
215 * is called.
216 * <p>This method may be called repeatedly to change content type and
217 * character encoding.
218 * This method has no effect if called after the response
219 * has been committed. It does not set the response's character
220 * encoding if it is called after <code>getWriter</code>
221 * has been called or after the response has been committed.
222 * <p>Containers must communicate the content type and the character
223 * encoding used for the servlet response's writer to the client if
224 * the protocol provides a way for doing so. In the case of HTTP,
225 * the <code>Content-Type</code> header is used.
226 *
227 * @param type a <code>String</code> specifying the MIME
228 * type of the content
229 *
230 * @see #setLocale
231 * @see #setCharacterEncoding
232 * @see #getOutputStream
233 * @see #getWriter
234 */
235 public void setContentType(String type);
236
237 /**
238 * Sets the preferred buffer size for the body of the response.
239 * The servlet container will use a buffer at least as large as
240 * the size requested. The actual buffer size used can be found
241 * using <code>getBufferSize</code>.
242 *
243 * <p>A larger buffer allows more content to be written before anything is
244 * actually sent, thus providing the servlet with more time to set
245 * appropriate status codes and headers. A smaller buffer decreases
246 * server memory load and allows the client to start receiving data more
247 * quickly.
248 *
249 * <p>This method must be called before any response body content is
250 * written; if content has been written or the response object has
251 * been committed, this method throws an
252 * <code>IllegalStateException</code>.
253 *
254 * @param size the preferred buffer size
255 *
256 * @exception IllegalStateException if this method is called after
257 * content has been written
258 *
259 * @see #getBufferSize
260 * @see #flushBuffer
261 * @see #isCommitted
262 * @see #reset
263 */
264 public void setBufferSize(int size);
265
266 /**
267 * Returns the actual buffer size used for the response. If no buffering
268 * is used, this method returns 0.
269 *
270 * @return the actual buffer size used
271 *
272 * @see #setBufferSize
273 * @see #flushBuffer
274 * @see #isCommitted
275 * @see #reset
276 */
277 public int getBufferSize();
278
279 /**
280 * Forces any content in the buffer to be written to the client. A call
281 * to this method automatically commits the response, meaning the status
282 * code and headers will be written.
283 *
284 * @see #setBufferSize
285 * @see #getBufferSize
286 * @see #isCommitted
287 * @see #reset
288 */
289 public void flushBuffer() throws IOException;
290
291 /**
292 * Clears the content of the underlying buffer in the response without
293 * clearing headers or status code. If the
294 * response has been committed, this method throws an
295 * <code>IllegalStateException</code>.
296 *
297 * @see #setBufferSize
298 * @see #getBufferSize
299 * @see #isCommitted
300 * @see #reset
301 *
302 * @since Servlet 2.3
303 */
304 public void resetBuffer();
305
306 /**
307 * Returns a boolean indicating if the response has been
308 * committed. A commited response has already had its status
309 * code and headers written.
310 *
311 * @return a boolean indicating if the response has been committed
312 *
313 * @see #setBufferSize
314 * @see #getBufferSize
315 * @see #flushBuffer
316 * @see #reset
317 */
318 public boolean isCommitted();
319
320 /**
321 * Clears any data that exists in the buffer as well as the status code and
322 * headers. If the response has been committed, this method throws an
323 * <code>IllegalStateException</code>.
324 *
325 * @exception IllegalStateException if the response has already been
326 * committed
327 *
328 * @see #setBufferSize
329 * @see #getBufferSize
330 * @see #flushBuffer
331 * @see #isCommitted
332 */
333 public void reset();
334
335 /**
336 * Sets the locale of the response, if the response has not been
337 * committed yet. It also sets the response's character encoding
338 * appropriately for the locale, if the character encoding has not
339 * been explicitly set using {@link #setContentType} or
340 * {@link #setCharacterEncoding}, <code>getWriter</code> hasn't
341 * been called yet, and the response hasn't been committed yet.
342 * If the deployment descriptor contains a
343 * <code>locale-encoding-mapping-list</code> element, and that
344 * element provides a mapping for the given locale, that mapping
345 * is used. Otherwise, the mapping from locale to character
346 * encoding is container dependent.
347 * <p>This method may be called repeatedly to change locale and
348 * character encoding. The method has no effect if called after the
349 * response has been committed. It does not set the response's
350 * character encoding if it is called after {@link #setContentType}
351 * has been called with a charset specification, after
352 * {@link #setCharacterEncoding} has been called, after
353 * <code>getWriter</code> has been called, or after the response
354 * has been committed.
355 * <p>Containers must communicate the locale and the character encoding
356 * used for the servlet response's writer to the client if the protocol
357 * provides a way for doing so. In the case of HTTP, the locale is
358 * communicated via the <code>Content-Language</code> header,
359 * the character encoding as part of the <code>Content-Type</code>
360 * header for text media types. Note that the character encoding
361 * cannot be communicated via HTTP headers if the servlet does not
362 * specify a content type; however, it is still used to encode text
363 * written via the servlet response's writer.
364 *
365 * @param loc the locale of the response
366 *
367 * @see #getLocale
368 * @see #setContentType
369 * @see #setCharacterEncoding
370 */
371 public void setLocale(Locale loc);
372
373 /**
374 * Returns the locale specified for this response
375 * using the {@link #setLocale} method. Calls made to
376 * <code>setLocale</code> after the response is committed
377 * have no effect. If no locale has been specified,
378 * the container's default locale is returned.
379 *
380 * @see #setLocale
381 */
382 public Locale getLocale();
383 }
384
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