ServletResponse.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jakarta.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.charset.Charset;
import java.util.Locale;
/**
* 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:
* <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>
*/
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 <code>String</code> specifying the content type, for example, <code>text/html; charset=UTF-8</code>, or
* null
*
* @since Servlet 2.4
*/
String getContentType();
/**
* 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
*/
ServletOutputStream getOutputStream() throws IOException;
/**
* 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
*/
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,
* {@link #setCharacterEncoding(Charset)}, {@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
* @see #setCharacterEncoding(Charset)
*
* @since Servlet 2.4
*/
void setCharacterEncoding(String charset);
/**
* 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 #setCharacterEncoding(String)}, {@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>StandardCharsets.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 encoding The encoding to use or {@code null}
*
* @see #setContentType #setLocale
* @see #setCharacterEncoding(String)
*
* @since Servlet 6.1
*/
default void setCharacterEncoding(Charset encoding) {
if (encoding == null) {
setCharacterEncoding((String) null);
} else {
setCharacterEncoding(encoding.name());
}
}
/**
* 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
*/
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.
*
* @param length an integer specifying the length of the content being returned to the client; sets the
* Content-Length header
*
* @since Servlet 3.1
*/
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,
* <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
*/
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 <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
*/
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
*/
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 #setBufferSize
* @see #getBufferSize
* @see #isCommitted
* @see #reset
*/
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 <code>IllegalStateException</code>.
*
* @see #setBufferSize
* @see #getBufferSize
* @see #isCommitted
* @see #reset
*
* @since Servlet 2.3
*/
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
*/
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 <code>IllegalStateException</code>.
*
* @exception IllegalStateException if the response has already been committed
*
* @see #setBufferSize
* @see #getBufferSize
* @see #flushBuffer
* @see #isCommitted
*/
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}, {@link #setCharacterEncoding(String)} or {@link #setCharacterEncoding(Charset)},
* <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(String)
* @see #setCharacterEncoding(Charset)
*/
void setLocale(Locale loc);
/**
* 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
*/
Locale getLocale();
}