jakarta.servlet.ServletResponse Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2023 Oracle and/or its affiliates and others.
* All rights reserved.
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
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 {@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 any of the following techniques: per
* request, per web-app (using {@link ServletContext#setRequestCharacterEncoding}, deployment descriptor), and per
* container (for all web applications deployed in that container, using vendor specific configuration). If multiple of
* the preceding techniques have been employed, the priority is the order listed. For per request, the charset for the
* response can be specified explicitly using the {@link #setCharacterEncoding(String)},
* {@link #setCharacterEncoding(Charset)} and {@link #setContentType} methods, or implicitly using the
* {@link #setLocale} method. Explicit specifications take precedence over implicit specifications. If no charset is
* explicitly 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.
*
* @author Various
*
* @see ServletOutputStream
*/
public interface ServletResponse {
/**
* Returns the name of the character encoding (MIME charset) used for the body sent in this response. The following
* methods for specifying the response character encoding are consulted, in decreasing order of priority: per request,
* perweb-app (using {@link ServletContext#setResponseCharacterEncoding}, deployment descriptor), and per container (for
* all web applications deployed in that container, using vendor specific configuration). The first one of these methods
* that yields a result is returned. Per-request, the charset for the response can be specified explicitly using the
* {@link #setCharacterEncoding(String)}, {@link #setCharacterEncoding(Charset)} and {@link #setContentType} methods, or
* implicitly using the setLocale(java.util.Locale) 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
*/
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} or {@link #getWriter} has been called, 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 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.
*
*
* Calling flush() on the ServletOutputStream commits the response.
*
* Either this method or {@link #getWriter} may be called to write the body, not both, except when {@link #reset} has
* been called.
*
* @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
* @see #reset
*/
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, except when {@link #reset}
* has been called.
*
* @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
* @see #reset
*/
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
* response character encoding has already been set by {@link ServletContext#setResponseCharacterEncoding}, the
* deployment descriptor, or using the {@link #setCharacterEncoding(Charset)}, {@link #setContentType} or
* {@link #setLocale} methods, the value set in this method overrides all of those values. Calling
* {@link #setContentType} with the String of text/html and calling this method with the
* String of UTF-8 is equivalent to calling {@link #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.
*
* If calling this method has an effect (as per the previous paragraph), calling this method with {@code null} clears
* any character encoding set via a previous call to this method, {@link #setCharacterEncoding(Charset)},
* {@link #setContentType} or {@link #setLocale} but does not affect any default character encoding configured via
* {@link ServletContext#setResponseCharacterEncoding} or the deployment descriptor.
*
* If this method is called with an invalid or unrecognised character encoding, then a subsequent call to
* {@link #getWriter()} will throw a {@link UnsupportedEncodingException}. Content for an unknown encoding can be sent
* with the {@link ServletOutputStream} returned from {@link #getOutputStream()}.
*
* Containers may choose to log calls to this method that use an invalid or unrecognised character encoding.
*
* 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 encoding a String specifying only the character set defined by IANA Character Sets
* (http://www.iana.org/assignments/character-sets) or {@code null}
*
* @see #setCharacterEncoding(Charset)
* @see #setContentType
* @see #setLocale
*
* @since Servlet 2.4
*/
void setCharacterEncoding(String encoding);
/**
* Sets the character encoding (MIME charset) of the response being sent to the client, for example, to UTF-8. If the
* response character encoding has already been set by {@link ServletContext#setResponseCharacterEncoding}, the
* deployment descriptor, or using the {@link #setCharacterEncoding(String)}, {@link #setContentType} or
* {@link #setLocale} methods, the value set in this method overrides all of those values. Calling
* {@link #setContentType} with the String of text/html and calling this method with
* {@link StandardCharsets#UTF_8} is equivalent to calling {@link #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.
*
* If calling this method has an effect (as per the previous paragraph), calling this method with {@code null} clears
* any character encoding set via a previous call to this method, {@link #setCharacterEncoding(String)},
* {@link #setContentType} or {@link #setLocale} but does not affect any default character encoding configured via
* {@link ServletContext#setResponseCharacterEncoding} or the deployment descriptor.
*
* 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.
*
* Implementations are strongly encouraged to override this default method and provide a more efficient implementation.
*
* @param encoding a Charset instance representing the encoding to use or {@code null}
*
* @see #setCharacterEncoding(String)
* @see #setContentType
* @see #setLocale
*
* @since Servlet 6.1
*/
default void setCharacterEncoding(Charset encoding) {
setCharacterEncoding(encoding.name());
}
/**
* Sets the length of the content body in the response In HTTP servlets, this method sets the HTTP Content-Length
* header.
*
* This method may be called repeatedly to change the content length. This method has no effect if called after the
* response has been committed.
*
* @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.
*
* This method may be called repeatedly to change the content length. This method has no effect if called after the
* response has been committed.
*
* @param len a long specifying the length of the content being returned to the client; sets the Content-Length header
*
* @since Servlet 3.1
*/
void setContentLengthLong(long len);
/**
* 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
* {@link #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.
*
* If calling this method has an effect (as per the previous paragraph), calling this method with {@code null} clears
* any content type set via a previous call to this method and clears any character encoding set via a previous call to
* this method, {@link #setCharacterEncoding(String)}, {@link #setCharacterEncoding(Charset)} or {@link #setLocale} but
* does not affect any default character encoding configured via {@link ServletContext#setResponseCharacterEncoding} or
* the deployment descriptor.
*
* If this method is called with an invalid or unrecognised character encoding, then a subsequent call to
* {@link #getWriter()} will throw a {@link UnsupportedEncodingException}. Content for an unknown encoding can be sent
* with the {@link ServletOutputStream} returned from {@link #getOutputStream()}.
*
* Containers may choose to log calls to this method that use an invalid or unrecognised character encoding.
*
* 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 or {@code null}
*
* @see #setLocale
* @see #setCharacterEncoding(String)
* @see #setCharacterEncoding(Charset)
* @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 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
*/
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.
*
* @see #setBufferSize
* @see #getBufferSize
* @see #isCommitted
* @see #reset
*
* @throws IOException if the act of flushing the buffer cannot be completed.
*
*/
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 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, headers. The state of calling
* {@link #getWriter} or {@link #getOutputStream} is also cleared. It is legal, for instance, to call
* {@link #getWriter}, {@link #reset} and then {@link #getOutputStream}. If {@link #getWriter} or
* {@link #getOutputStream} have been called before this method, then the corrresponding returned Writer or OutputStream
* will be staled and the behavior of using the stale object is undefined. 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
*/
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)},
* 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(String)} has
* been called, after {@link #setCharacterEncoding(Charset)} has been called, after getWriter has been
* called, or after the response has been committed.
*
* If calling this method has an effect on the locale (as per the previous paragraph), calling this method with
* {@code null} clears any locale set via a previous call to this method. If calling this method has an effect on the
* character encoding, calling this method with {@code null} clears the previously set character encoding.
*
* 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 or {code @null}
*
* @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
* setLocale after the response is committed have no effect. If no locale has been specified, the
* container's default locale is returned.
*
* @return the Locale for this response.
*
* @see #setLocale
*/
Locale getLocale();
}