ServletResponse object and
+ * passes it as an argument to the servlet's service method.
+ *
+ * To send binary data in a MIME body response, use the
+ * {@link ServletOutputStream} returned by {@link #getOutputStream}. To send
+ * character data, use the PrintWriter object returned by
+ * {@link #getWriter}. To mix binary and text data, for example, to create a
+ * multipart response, use a ServletOutputStream and manage the
+ * character sections manually.
+ *
+ * The charset for the MIME body response can be specified explicitly using the
+ * {@link #setCharacterEncoding} and {@link #setContentType} methods, or
+ * implicitly using the {@link #setLocale} method. Explicit specifications take
+ * precedence over implicit specifications. If no charset is specified,
+ * ISO-8859-1 will be used. The setCharacterEncoding,
+ * setContentType, or setLocale method must be called
+ * before getWriter and before committing the response for the
+ * character encoding to be used.
+ *
+ * See the Internet RFCs such as
+ * RFC 2045 for more information on MIME. Protocols such as SMTP and HTTP
+ * define profiles of MIME, and those standards are still evolving.
+ *
+ * @see ServletOutputStream
+ */
+public interface ServletResponse {
+
+ /**
+ * Returns the name of the character encoding (MIME charset) used for the
+ * body sent in this response. The character encoding may have been
+ * specified explicitly using the {@link #setCharacterEncoding} or
+ * {@link #setContentType} methods, or implicitly using the
+ * {@link #setLocale} method. Explicit specifications take precedence over
+ * implicit specifications. Calls made to these methods after
+ * getWriter has been called or after the response has been
+ * committed have no effect on the character encoding. If no character
+ * encoding has been specified, ISO-8859-1 is returned.
+ *
+ * See RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt) for more information
+ * about character encoding and MIME.
+ *
+ * @return a String specifying the name of the character
+ * encoding, for example, UTF-8
+ */
+ public String getCharacterEncoding();
+
+ /**
+ * Returns the content type used for the MIME body sent in this response.
+ * The content type proper must have been specified using
+ * {@link #setContentType} before the response is committed. If no content
+ * type has been specified, this method returns null. If a content type has
+ * been specified and a character encoding has been explicitly or implicitly
+ * specified as described in {@link #getCharacterEncoding}, the charset
+ * parameter is included in the string returned. If no character encoding
+ * has been specified, the charset parameter is omitted.
+ *
+ * @return a String specifying the content type, for example,
+ * text/html; charset=UTF-8, or null
+ * @since 2.4
+ */
+ public String getContentType();
+
+ /**
+ * Returns a {@link ServletOutputStream} suitable for writing binary data in
+ * the response. The servlet container does not encode the binary data.
+ *
+ * Calling flush() on the ServletOutputStream commits the response. Either
+ * this method or {@link #getWriter} may be called to write the body, not
+ * both.
+ *
+ * @return a {@link ServletOutputStream} for writing binary data
+ * @exception IllegalStateException
+ * if the getWriter method has been called on
+ * this response
+ * @exception IOException
+ * if an input or output exception occurred
+ * @see #getWriter
+ */
+ public ServletOutputStream getOutputStream() throws IOException;
+
+ /**
+ * Returns a PrintWriter object that can send character text to
+ * the client. The PrintWriter uses the character encoding
+ * returned by {@link #getCharacterEncoding}. If the response's character
+ * encoding has not been specified as described in
+ * getCharacterEncoding (i.e., the method just returns the
+ * default value ISO-8859-1), getWriter updates it
+ * to ISO-8859-1.
+ *
+ * Calling flush() on the PrintWriter commits the response.
+ *
+ * Either this method or {@link #getOutputStream} may be called to write the
+ * body, not both.
+ *
+ * @return a PrintWriter object that can return character data
+ * to the client
+ * @exception java.io.UnsupportedEncodingException
+ * if the character encoding returned by
+ * getCharacterEncoding cannot be used
+ * @exception IllegalStateException
+ * if the getOutputStream method has already
+ * been called for this response object
+ * @exception IOException
+ * if an input or output exception occurred
+ * @see #getOutputStream
+ * @see #setCharacterEncoding
+ */
+ public PrintWriter getWriter() throws IOException;
+
+ /**
+ * Sets the character encoding (MIME charset) of the response being sent to
+ * the client, for example, to UTF-8. If the character encoding has already
+ * been set by {@link #setContentType} or {@link #setLocale}, this method
+ * overrides it. Calling {@link #setContentType} with the
+ * String of text/html and calling this method
+ * with the String of UTF-8 is equivalent with
+ * calling setContentType with the String of
+ * text/html; charset=UTF-8.
+ *
+ * This method can be called repeatedly to change the character encoding.
+ * This method has no effect if it is called after getWriter
+ * has been called or after the response has been committed.
+ *
+ * Containers must communicate the character encoding used for the servlet
+ * response's writer to the client if the protocol provides a way for doing
+ * so. In the case of HTTP, the character encoding is communicated as part
+ * of the Content-Type header for text media types. Note that
+ * the character encoding cannot be communicated via HTTP headers if the
+ * servlet does not specify a content type; however, it is still used to
+ * encode text written via the servlet response's writer.
+ *
+ * @param charset
+ * a String specifying only the character set defined by IANA
+ * Character Sets
+ * (http://www.iana.org/assignments/character-sets)
+ * @see #setContentType #setLocale
+ * @since 2.4
+ */
+ public void setCharacterEncoding(String charset);
+
+ /**
+ * Sets the length of the content body in the response In HTTP servlets,
+ * this method sets the HTTP Content-Length header.
+ *
+ * @param len
+ * an integer specifying the length of the content being returned
+ * to the client; sets the Content-Length header
+ */
+ public void setContentLength(int len);
+
+ /**
+ * TODO SERVLET 3.1
+ */
+ public void setContentLengthLong(long length);
+
+ /**
+ * Sets the content type of the response being sent to the client, if the
+ * response has not been committed yet. The given content type may include a
+ * character encoding specification, for example,
+ * text/html;charset=UTF-8. The response's character encoding
+ * is only set from the given content type if this method is called before
+ * getWriter is called.
+ *
+ * This method may be called repeatedly to change content type and character
+ * encoding. This method has no effect if called after the response has been
+ * committed. It does not set the response's character encoding if it is
+ * called after getWriter has been called or after the response
+ * has been committed.
+ *
+ * Containers must communicate the content type and the character encoding
+ * used for the servlet response's writer to the client if the protocol
+ * provides a way for doing so. In the case of HTTP, the
+ * Content-Type header is used.
+ *
+ * @param type
+ * a String specifying the MIME type of the content
+ * @see #setLocale
+ * @see #setCharacterEncoding
+ * @see #getOutputStream
+ * @see #getWriter
+ */
+ public void setContentType(String type);
+
+ /**
+ * Sets the preferred buffer size for the body of the response. The servlet
+ * container will use a buffer at least as large as the size requested. The
+ * actual buffer size used can be found using getBufferSize.
+ *
+ * A larger buffer allows more content to be written before anything is + * actually sent, thus providing the servlet with more time to set + * appropriate status codes and headers. A smaller buffer decreases server + * memory load and allows the client to start receiving data more quickly. + *
+ * This method must be called before any response body content is written;
+ * if content has been written or the response object has been committed,
+ * this method throws an IllegalStateException.
+ *
+ * @param size
+ * the preferred buffer size
+ * @exception IllegalStateException
+ * if this method is called after content has been written
+ * @see #getBufferSize
+ * @see #flushBuffer
+ * @see #isCommitted
+ * @see #reset
+ */
+ public void setBufferSize(int size);
+
+ /**
+ * Returns the actual buffer size used for the response. If no buffering is
+ * used, this method returns 0.
+ *
+ * @return the actual buffer size used
+ * @see #setBufferSize
+ * @see #flushBuffer
+ * @see #isCommitted
+ * @see #reset
+ */
+ public int getBufferSize();
+
+ /**
+ * Forces any content in the buffer to be written to the client. A call to
+ * this method automatically commits the response, meaning the status code
+ * and headers will be written.
+ *
+ * @see #setBufferSize
+ * @see #getBufferSize
+ * @see #isCommitted
+ * @see #reset
+ */
+ public void flushBuffer() throws IOException;
+
+ /**
+ * Clears the content of the underlying buffer in the response without
+ * clearing headers or status code. If the response has been committed, this
+ * method throws an IllegalStateException.
+ *
+ * @see #setBufferSize
+ * @see #getBufferSize
+ * @see #isCommitted
+ * @see #reset
+ * @since 2.3
+ */
+ public void resetBuffer();
+
+ /**
+ * Returns a boolean indicating if the response has been committed. A
+ * committed response has already had its status code and headers written.
+ *
+ * @return a boolean indicating if the response has been committed
+ * @see #setBufferSize
+ * @see #getBufferSize
+ * @see #flushBuffer
+ * @see #reset
+ */
+ public boolean isCommitted();
+
+ /**
+ * Clears any data that exists in the buffer as well as the status code and
+ * headers. If the response has been committed, this method throws an
+ * IllegalStateException.
+ *
+ * @exception IllegalStateException
+ * if the response has already been committed
+ * @see #setBufferSize
+ * @see #getBufferSize
+ * @see #flushBuffer
+ * @see #isCommitted
+ */
+ public void reset();
+
+ /**
+ * Sets the locale of the response, if the response has not been committed
+ * yet. It also sets the response's character encoding appropriately for the
+ * locale, if the character encoding has not been explicitly set using
+ * {@link #setContentType} or {@link #setCharacterEncoding},
+ * getWriter hasn't been called yet, and the response hasn't
+ * been committed yet. If the deployment descriptor contains a
+ * locale-encoding-mapping-list element, and that element
+ * provides a mapping for the given locale, that mapping is used. Otherwise,
+ * the mapping from locale to character encoding is container dependent.
+ *
+ * This method may be called repeatedly to change locale and character
+ * encoding. The method has no effect if called after the response has been
+ * committed. It does not set the response's character encoding if it is
+ * called after {@link #setContentType} has been called with a charset
+ * specification, after {@link #setCharacterEncoding} has been called, after
+ * getWriter has been called, or after the response has been
+ * committed.
+ *
+ * Containers must communicate the locale and the character encoding used
+ * for the servlet response's writer to the client if the protocol provides
+ * a way for doing so. In the case of HTTP, the locale is communicated via
+ * the Content-Language header, the character encoding as part
+ * of the Content-Type header for text media types. Note that
+ * the character encoding cannot be communicated via HTTP headers if the
+ * servlet does not specify a content type; however, it is still used to
+ * encode text written via the servlet response's writer.
+ *
+ * @param loc
+ * the locale of the response
+ * @see #getLocale
+ * @see #setContentType
+ * @see #setCharacterEncoding
+ */
+ public void setLocale(Locale loc);
+
+ /**
+ * Returns the locale specified for this response using the
+ * {@link #setLocale} method. Calls made to setLocale after the
+ * response is committed have no effect. If no locale has been specified,
+ * the container's default locale is returned.
+ *
+ * @see #setLocale
+ */
+ public Locale getLocale();
+
+}