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package jakarta.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Locale;

Defines an object to assist a servlet in sending a response to the client. The servlet container creates a 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 ServletOutputStream returned by getOutputStream. To send character data, use the PrintWriter object returned by 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 or implicitly. The priority order for specifying the response body is:

  1. explicitly per request using setCharacterEncoding and setContentType
  2. implicitly per request using setLocale
  3. per web application via the deployment descriptor or ServletContext.setRequestCharacterEncoding(String)
  4. container default via vendor specific configuration
  5. ISO-8859-1
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 Also:
/** * Defines an object to assist a servlet in sending a response to the client. * The servlet container creates a <code>ServletResponse</code> object and * passes it as an argument to the servlet's <code>service</code> method. * <p> * To send binary data in a MIME body response, use the * {@link ServletOutputStream} returned by {@link #getOutputStream}. To send * character data, use the <code>PrintWriter</code> object returned by * {@link #getWriter}. To mix binary and text data, for example, to create a * multipart response, use a <code>ServletOutputStream</code> and manage the * character sections manually. * <p> * The charset for the MIME body response can be specified explicitly or * implicitly. The priority order for specifying the response body is: * <ol> * <li>explicitly per request using {@link #setCharacterEncoding} and * {@link #setContentType}</li> * <li>implicitly per request using {@link #setLocale}</li> * <li>per web application via the deployment descriptor or * {@link ServletContext#setRequestCharacterEncoding(String)}</li> * <li>container default via vendor specific configuration</li> * <li>ISO-8859-1</li> * </ol> * The <code>setCharacterEncoding</code>, <code>setContentType</code>, or * <code>setLocale</code> method must be called before <code>getWriter</code> * and before committing the response for the character encoding to be used. * <p> * See the Internet RFCs such as <a href="http://www.ietf.org/rfc/rfc2045.txt"> * RFC 2045</a> 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 charset for the MIME body response can be specified explicitly or implicitly. The priority order for specifying the response body is:
  1. explicitly per request using setCharacterEncoding and setContentType
  2. implicitly per request using setLocale
  3. per web application via the deployment descriptor or ServletContext.setRequestCharacterEncoding(String)
  4. container default via vendor specific configuration
  5. ISO-8859-1
Calls made to setCharacterEncoding, setContentType or setLocale 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.

Returns:a String specifying the name of the character encoding, for example, UTF-8
/** * Returns the name of the character encoding (MIME charset) used for the * body sent in this response. * The charset for the MIME body response can be specified explicitly or * implicitly. The priority order for specifying the response body is: * <ol> * <li>explicitly per request using {@link #setCharacterEncoding} and * {@link #setContentType}</li> * <li>implicitly per request using {@link #setLocale}</li> * <li>per web application via the deployment descriptor or * {@link ServletContext#setRequestCharacterEncoding(String)}</li> * <li>container default via vendor specific configuration</li> * <li>ISO-8859-1</li> * </ol> * Calls made to {@link #setCharacterEncoding}, {@link #setContentType} or * {@link #setLocale} after <code>getWriter</code> has been called or after * the response has been committed have no effect on the character encoding. * If no character encoding has been specified, <code>ISO-8859-1</code> is * returned. * <p> * See RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt) for more information * about character encoding and MIME. * * @return a <code>String</code> specifying the name of the character * encoding, for example, <code>UTF-8</code> */
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 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 getCharacterEncoding, the charset parameter is included in the string returned. If no character encoding has been specified, the charset parameter is omitted.
Returns:a String specifying the content type, for example, text/html; charset=UTF-8, or null
Since:2.4
/** * 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 <code>String</code> specifying the content type, for example, * <code>text/html; charset=UTF-8</code>, or null * @since 2.4 */
public String getContentType();
Returns a 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 getWriter may be called to write the body, not both.

Throws:
See Also:
Returns:a ServletOutputStream for writing binary data
/** * Returns a {@link ServletOutputStream} suitable for writing binary data in * the response. The servlet container does not encode the binary data. * <p> * 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 <code>getWriter</code> 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 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 getOutputStream may be called to write the body, not both.

Throws:
See Also:
Returns:a PrintWriter object that can return character data to the client
/** * Returns a <code>PrintWriter</code> object that can send character text to * the client. The <code>PrintWriter</code> uses the character encoding * returned by {@link #getCharacterEncoding}. If the response's character * encoding has not been specified as described in * <code>getCharacterEncoding</code> (i.e., the method just returns the * default value <code>ISO-8859-1</code>), <code>getWriter</code> updates it * to <code>ISO-8859-1</code>. * <p> * Calling flush() on the <code>PrintWriter</code> commits the response. * <p> * Either this method or {@link #getOutputStream} may be called to write the * body, not both. * * @return a <code>PrintWriter</code> object that can return character data * to the client * @exception java.io.UnsupportedEncodingException * if the character encoding returned by * <code>getCharacterEncoding</code> cannot be used * @exception IllegalStateException * if the <code>getOutputStream</code> 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 container default, ServletContext default, setContentType or setLocale, this method overrides it. Calling 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.

Params:
  • charset – a String specifying only the character set defined by IANA Character Sets (http://www.iana.org/assignments/character-sets)
See Also:
Since:2.4
/** * 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 container default, ServletContext default, * {@link #setContentType} or {@link #setLocale}, this method overrides it. * Calling {@link #setContentType} with the <code>String</code> of * <code>text/html</code> and calling this method with the * <code>String</code> of <code>UTF-8</code> is equivalent with calling * <code>setContentType</code> with the <code>String</code> of * <code>text/html; charset=UTF-8</code>. * <p> * This method can be called repeatedly to change the character encoding. * This method has no effect if it is called after <code>getWriter</code> * has been called or after the response has been committed. * <p> * 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 <code>Content-Type</code> 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.
Params:
  • len – an integer specifying the length of the content being returned to the client; sets the Content-Length header
/** * 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);
Sets the length of the content body in the response In HTTP servlets, this method sets the HTTP Content-Length header.
Params:
  • length – an integer specifying the length of the content being returned to the client; sets the Content-Length header
Since:Servlet 3.1
/** * Sets the length of the content body in the response In HTTP servlets, * this method sets the HTTP Content-Length header. * * @param length * an integer specifying the length of the content being returned * to the client; sets the Content-Length header * * @since 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.

Params:
  • type – a String specifying the MIME type of the content
See Also:
/** * 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, * <code>text/html;charset=UTF-8</code>. The response's character encoding * is only set from the given content type if this method is called before * <code>getWriter</code> is called. * <p> * 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 <code>getWriter</code> has been called or after the response * has been committed. * <p> * 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 * <code>Content-Type</code> header is used. * * @param type * a <code>String</code> 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.

Params:
  • size – the preferred buffer size
Throws:
See Also:
/** * 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 <code>getBufferSize</code>. * <p> * 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. * <p> * 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 <code>IllegalStateException</code>. * * @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.
See Also:
Returns:the actual buffer size used
/** * 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.
Throws:
  • IOException – if an I/O occurs during the flushing of the response
See Also:
/** * 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. * * @throws IOException if an I/O occurs during the flushing of the response * * @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 Also:
Since:2.3
/** * 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 <code>IllegalStateException</code>. * * @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.
See Also:
Returns:a boolean indicating if the response has been committed
/** * 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.
Throws:
  • IllegalStateException – if the response has already been committed
See Also:
/** * 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 * <code>IllegalStateException</code>. * * @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 setContentType or 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 setContentType has been called with a charset specification, after 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.

Params:
  • loc – the locale of the response
See Also:
/** * 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}, * <code>getWriter</code> hasn't been called yet, and the response hasn't * been committed yet. If the deployment descriptor contains a * <code>locale-encoding-mapping-list</code> 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. * <p> * 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 * <code>getWriter</code> has been called, or after the response has been * committed. * <p> * 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 <code>Content-Language</code> header, the character encoding as part * of the <code>Content-Type</code> 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 setLocale method. Calls made to setLocale after the response is committed have no effect.
See Also:
Returns:The locale specified for this response using the setLocale method. If no locale has been specified, the container's default locale is returned.
/** * Returns the locale specified for this response using the * {@link #setLocale} method. Calls made to <code>setLocale</code> after the * response is committed have no effect. * * @return The locale specified for this response using the * {@link #setLocale} method. If no locale has been specified, the * container's default locale is returned. * * @see #setLocale */
public Locale getLocale(); }