FileDocCategorySizeDatePackage
ServletResponse.javaAPI DocApache Tomcat 6.0.1416110Fri Jul 20 04:20:34 BST 2007javax.servlet

ServletResponse

public interface ServletResponse
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 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.

author
Various
version
$Version$
see
ServletOutputStream

Fields Summary
Constructors Summary
Methods Summary
public voidflushBuffer()
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 intgetBufferSize()
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 java.lang.StringgetCharacterEncoding()
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 java.lang.StringgetContentType()
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 java.util.LocalegetLocale()
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 javax.servlet.ServletOutputStreamgetOutputStream()
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 java.io.PrintWritergetWriter()
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
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 booleanisCommitted()
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 voidreset()
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 voidresetBuffer()
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 voidsetBufferSize(int size)
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 voidsetCharacterEncoding(java.lang.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 {@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 voidsetContentLength(int len)
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 voidsetContentType(java.lang.String type)
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 voidsetLocale(java.util.Locale loc)
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