ServletResponse


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14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17  package javax.servlet;
18  
19  import java.io.IOException  ;
20  import java.io.PrintWriter  ;
21  import java.util.Locale  ;
22  
23  
24  /**
25   * Defines an object to assist a servlet in sending a response to the client.
26   * The servlet container creates a <code>ServletResponse</code> object and
27   * passes it as an argument to the servlet's <code>service</code> method.
28   *
29   * <p>To send binary data in a MIME body response, use
30   * the {@link ServletOutputStream} returned by {@link #getOutputStream}.
31   * To send character data, use the <code>PrintWriter</code> object 
32   * returned by {@link #getWriter}. To mix binary and text data,
33   * for example, to create a multipart response, use a
34   * <code>ServletOutputStream</code> and manage the character sections
35   * manually.
36   *
37   * <p>The charset for the MIME body response can be specified
38   * explicitly using the {@link #setCharacterEncoding} and
39   * {@link #setContentType} methods, or implicitly
40   * using the {@link #setLocale} method.
41   * Explicit specifications take precedence over
42   * implicit specifications. If no charset is specified, ISO-8859-1 will be
43   * used. The <code>setCharacterEncoding</code>,
44   * <code>setContentType</code>, or <code>setLocale</code> method must
45   * be called before <code>getWriter</code> and before committing
46   * the response for the character encoding to be used.
47   * 
48   * <p>See the Internet RFCs such as 
49   * <a HREF="http://www.ietf.org/rfc/rfc2045.txt">
50   * RFC 2045</a> for more information on MIME. Protocols such as SMTP
51   * and HTTP define profiles of MIME, and those standards
52   * are still evolving.
53   *
54   * @author  Various
55   * @version     $Version$
56   *
57   * @see     ServletOutputStream
58   *
59   */
60   
61  public interface ServletResponse {
62  
63  
64      
65      /**
66       * Returns the name of the character encoding (MIME charset)
67       * used for the body sent in this response.
68       * The character encoding may have been specified explicitly
69       * using the {@link #setCharacterEncoding} or
70       * {@link #setContentType} methods, or implicitly using the
71       * {@link #setLocale} method. Explicit specifications take
72       * precedence over implicit specifications. Calls made
73       * to these methods after <code>getWriter</code> has been
74       * called or after the response has been committed have no
75       * effect on the character encoding. If no character encoding
76       * has been specified, <code>ISO-8859-1</code> is returned.
77       * <p>See RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt)
78       * for more information about character encoding and MIME.
79       *
80       * @return      a <code>String</code> specifying the
81       *          name of the character encoding, for
82       *          example, <code>UTF-8</code>
83       *
84       */
85    
86      public String   getCharacterEncoding();
87      
88      
89  
90      /**
91       * Returns the content type used for the MIME body
92       * sent in this response. The content type proper must
93       * have been specified using {@link #setContentType}
94       * before the response is committed. If no content type
95       * has been specified, this method returns null.
96       * If a content type has been specified and a
97       * character encoding has been explicitly or implicitly
98       * specified as described in {@link #getCharacterEncoding},
99       * the charset parameter is included in the string returned.
100      * If no character encoding has been specified, the
101      * charset parameter is omitted.
102      *
103      * @return      a <code>String</code> specifying the
104      *          content type, for example,
105      *          <code>text/html; charset=UTF-8</code>,
106      *          or null
107      *
108      * @since 2.4
109      */
110   
111     public String   getContentType();
112     
113     
114 
115     /**
116      * Returns a {@link ServletOutputStream} suitable for writing binary 
117      * data in the response. The servlet container does not encode the
118      * binary data.  
119      
120      * <p> Calling flush() on the ServletOutputStream commits the response.
121      
122      * Either this method or {@link #getWriter} may 
123      * be called to write the body, not both.
124      *
125      * @return              a {@link ServletOutputStream} for writing binary data   
126      *
127      * @exception IllegalStateException if the <code>getWriter</code> method
128      *                  has been called on this response
129      *
130      * @exception IOException       if an input or output exception occurred
131      *
132      * @see                 #getWriter
133      *
134      */
135 
136     public ServletOutputStream   getOutputStream() throws IOException  ;
137     
138     
139 
140     /**
141      * Returns a <code>PrintWriter</code> object that
142      * can send character text to the client.
143      * The <code>PrintWriter</code> uses the character
144      * encoding returned by {@link #getCharacterEncoding}.
145      * If the response's character encoding has not been
146      * specified as described in <code>getCharacterEncoding</code>
147      * (i.e., the method just returns the default value 
148      * <code>ISO-8859-1</code>), <code>getWriter</code>
149      * updates it to <code>ISO-8859-1</code>.
150      * <p>Calling flush() on the <code>PrintWriter</code>
151      * commits the response.
152      * <p>Either this method or {@link #getOutputStream} may be called
153      * to write the body, not both.
154      *
155      * 
156      * @return      a <code>PrintWriter</code> object that 
157      *          can return character data to the client 
158      *
159      * @exception UnsupportedEncodingException
160      *          if the character encoding returned
161      *          by <code>getCharacterEncoding</code> cannot be used
162      *
163      * @exception IllegalStateException
164      *          if the <code>getOutputStream</code>
165      *          method has already been called for this 
166      *          response object
167      *
168      * @exception IOException
169      *          if an input or output exception occurred
170      *
171      * @see         #getOutputStream
172      * @see         #setCharacterEncoding
173      *
174      */
175 
176     public PrintWriter   getWriter() throws IOException  ;
177     
178     
179     
180     
181     /**
182      * Sets the character encoding (MIME charset) of the response
183      * being sent to the client, for example, to UTF-8.
184      * If the character encoding has already been set by
185      * {@link #setContentType} or {@link #setLocale},
186      * this method overrides it.
187      * Calling {@link #setContentType} with the <code>String</code>
188      * of <code>text/html</code> and calling
189      * this method with the <code>String</code> of <code>UTF-8</code>
190      * is equivalent with calling
191      * <code>setContentType</code> with the <code>String</code> of
192      * <code>text/html; charset=UTF-8</code>.
193      * <p>This method can be called repeatedly to change the character
194      * encoding.
195      * This method has no effect if it is called after
196      * <code>getWriter</code> has been
197      * called or after the response has been committed.
198      * <p>Containers must communicate the character encoding used for
199      * the servlet response's writer to the client if the protocol
200      * provides a way for doing so. In the case of HTTP, the character
201      * encoding is communicated as part of the <code>Content-Type</code>
202      * header for text media types. Note that the character encoding
203      * cannot be communicated via HTTP headers if the servlet does not
204      * specify a content type; however, it is still used to encode text
205      * written via the servlet response's writer.
206      *
207      * @param charset   a String specifying only the character set
208      *          defined by IANA Character Sets
209      *          (http://www.iana.org/assignments/character-sets)
210      *
211      * @see     #setContentType
212      *          #setLocale
213      *
214      * @since 2.4
215      *
216      */
217 
218     public void setCharacterEncoding(String   charset);
219     
220     
221 
222 
223     /**
224      * Sets the length of the content body in the response
225      * In HTTP servlets, this method sets the HTTP Content-Length header.
226      *
227      *
228      * @param len   an integer specifying the length of the 
229      *          content being returned to the client; sets
230      *          the Content-Length header
231      *
232      */
233 
234     public void setContentLength(int len);
235     
236     
237 
238     /**
239      * Sets the content type of the response being sent to
240      * the client, if the response has not been committed yet.
241      * The given content type may include a character encoding
242      * specification, for example, <code>text/html;charset=UTF-8</code>.
243      * The response's character encoding is only set from the given
244      * content type if this method is called before <code>getWriter</code>
245      * is called.
246      * <p>This method may be called repeatedly to change content type and
247      * character encoding.
248      * This method has no effect if called after the response
249      * has been committed. It does not set the response's character
250      * encoding if it is called after <code>getWriter</code>
251      * has been called or after the response has been committed.
252      * <p>Containers must communicate the content type and the character
253      * encoding used for the servlet response's writer to the client if
254      * the protocol provides a way for doing so. In the case of HTTP,
255      * the <code>Content-Type</code> header is used.
256      *
257      * @param type  a <code>String</code> specifying the MIME 
258      *          type of the content
259      *
260      * @see         #setLocale
261      * @see         #setCharacterEncoding
262      * @see         #getOutputStream
263      * @see         #getWriter
264      *
265      */
266 
267     public void setContentType(String   type);
268     
269 
270     /**
271      * Sets the preferred buffer size for the body of the response.  
272      * The servlet container will use a buffer at least as large as 
273      * the size requested.  The actual buffer size used can be found
274      * using <code>getBufferSize</code>.
275      *
276      * <p>A larger buffer allows more content to be written before anything is
277      * actually sent, thus providing the servlet with more time to set
278      * appropriate status codes and headers.  A smaller buffer decreases 
279      * server memory load and allows the client to start receiving data more
280      * quickly.
281      *
282      * <p>This method must be called before any response body content is
283      * written; if content has been written or the response object has
284      * been committed, this method throws an 
285      * <code>IllegalStateException</code>.
286      *
287      * @param size  the preferred buffer size
288      *
289      * @exception  IllegalStateException    if this method is called after
290      *                      content has been written
291      *
292      * @see         #getBufferSize
293      * @see         #flushBuffer
294      * @see         #isCommitted
295      * @see         #reset
296      *
297      */
298 
299     public void setBufferSize(int size);
300     
301     
302 
303     /**
304      * Returns the actual buffer size used for the response.  If no buffering
305      * is used, this method returns 0.
306      *
307      * @return      the actual buffer size used
308      *
309      * @see         #setBufferSize
310      * @see         #flushBuffer
311      * @see         #isCommitted
312      * @see         #reset
313      *
314      */
315 
316     public int getBufferSize();
317     
318     
319 
320     /**
321      * Forces any content in the buffer to be written to the client.  A call
322      * to this method automatically commits the response, meaning the status 
323      * code and headers will be written.
324      *
325      * @see         #setBufferSize
326      * @see         #getBufferSize
327      * @see         #isCommitted
328      * @see         #reset
329      *
330      */
331 
332     public void flushBuffer() throws IOException  ;
333     
334     
335     
336     /**
337      * Clears the content of the underlying buffer in the response without
338      * clearing headers or status code. If the 
339      * response has been committed, this method throws an 
340      * <code>IllegalStateException</code>.
341      *
342      * @see         #setBufferSize
343      * @see         #getBufferSize
344      * @see         #isCommitted
345      * @see         #reset
346      *
347      * @since 2.3
348      */
349 
350     public void resetBuffer();
351     
352 
353     /**
354      * Returns a boolean indicating if the response has been
355      * committed.  A committed response has already had its status 
356      * code and headers written.
357      *
358      * @return      a boolean indicating if the response has been
359      *          committed
360      *
361      * @see         #setBufferSize
362      * @see         #getBufferSize
363      * @see         #flushBuffer
364      * @see         #reset
365      *
366      */
367 
368     public boolean isCommitted();
369     
370     
371 
372     /**
373      * Clears any data that exists in the buffer as well as the status code and
374      * headers.  If the response has been committed, this method throws an 
375      * <code>IllegalStateException</code>.
376      *
377      * @exception IllegalStateException  if the response has already been
378      *                                   committed
379      *
380      * @see         #setBufferSize
381      * @see         #getBufferSize
382      * @see         #flushBuffer
383      * @see         #isCommitted
384      *
385      */
386 
387     public void reset();
388     
389     
390 
391     /**
392      * Sets the locale of the response, if the response has not been
393      * committed yet. It also sets the response's character encoding
394      * appropriately for the locale, if the character encoding has not
395      * been explicitly set using {@link #setContentType} or
396      * {@link #setCharacterEncoding}, <code>getWriter</code> hasn't
397      * been called yet, and the response hasn't been committed yet.
398      * If the deployment descriptor contains a 
399      * <code>locale-encoding-mapping-list</code> element, and that
400      * element provides a mapping for the given locale, that mapping
401      * is used. Otherwise, the mapping from locale to character
402      * encoding is container dependent.
403      * <p>This method may be called repeatedly to change locale and
404      * character encoding. The method has no effect if called after the
405      * response has been committed. It does not set the response's
406      * character encoding if it is called after {@link #setContentType}
407      * has been called with a charset specification, after
408      * {@link #setCharacterEncoding} has been called, after
409      * <code>getWriter</code> has been called, or after the response
410      * has been committed.
411      * <p>Containers must communicate the locale and the character encoding
412      * used for the servlet response's writer to the client if the protocol
413      * provides a way for doing so. In the case of HTTP, the locale is
414      * communicated via the <code>Content-Language</code> header,
415      * the character encoding as part of the <code>Content-Type</code>
416      * header for text media types. Note that the character encoding
417      * cannot be communicated via HTTP headers if the servlet does not
418      * specify a content type; however, it is still used to encode text
419      * written via the servlet response's writer.
420      * 
421      * @param loc  the locale of the response
422      *
423      * @see         #getLocale
424      * @see         #setContentType
425      * @see         #setCharacterEncoding
426      *
427      */
428 
429     public void setLocale(Locale   loc);
430     
431     
432 
433     /**
434      * Returns the locale specified for this response
435      * using the {@link #setLocale} method. Calls made to
436      * <code>setLocale</code> after the response is committed
437      * have no effect. If no locale has been specified,
438      * the container's default locale is returned.
439      * 
440      * @see         #setLocale
441      *
442      */
443 
444     public Locale   getLocale();
445 
446 
447 
448 }
449 
450 
451 
452 
453 
454
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