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ServletResponse (Servlet and JavaServer Pages API Documentation)

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javax.servlet
Interface ServletResponse

All Known Subinterfaces:: HttpServletResponse

All Known Implementing Classes:: HttpServletResponseWrapper, ServletResponseWrapper

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 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 with setContentType(java.lang.String). For example, "text/html; charset=Shift_JIS". The charset can alternately be set using setLocale(java.util.Locale). If no charset is specified, ISO-8859-1 will be used. The setContentType or setLocale method must be called before getWriter for the charset to affect the construction of the writer.

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.

Version:: $Version$
Author:: Various
See Also:: ServletOutputStream

Method Summary

void flushBuffer()
          Forces any content in the buffer to be written to the client.

int getBufferSize()
          Returns the actual buffer size used for the response.

java.lang.String getCharacterEncoding()
          Returns the name of the charset used for the MIME body sent in this response.

java.util.Locale getLocale()
          Returns the locale assigned to the response.

ServletOutputStream getOutputStream()
          Returns a ServletOutputStream suitable for writing binary data in the response.

java.io.PrintWriter getWriter()
          Returns a PrintWriter object that can send character text to the client.

boolean isCommitted()
          Returns a boolean indicating if the response has been committed.

void reset()
          Clears any data that exists in the buffer as well as the status code and headers.

void resetBuffer()
          Clears the content of the underlying buffer in the response without clearing headers or status code.

void setBufferSize(int size)
          Sets the preferred buffer size for the body of the response.

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.

void setContentType(java.lang.String type)
          Sets the content type of the response being sent to the client.

void setLocale(java.util.Locale loc)
          Sets the locale of the response, setting the headers (including the Content-Type's charset) as appropriate.

Method Detail

getCharacterEncoding


public java.lang.String getCharacterEncoding()

Returns the name of the charset used for the MIME body sent in this response.

If no charset has been assigned, it is implicitly set to ISO-8859-1 (Latin-1).

See RFC 2047 (http://ds.internic.net/rfc/rfc2045.txt) for more information about character encoding and MIME.

Returns:: a String specifying the name of the charset, for example, ISO-8859-1

getOutputStream


public ServletOutputStream getOutputStream()
                                    throws java.io.IOException

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.

Returns:: a ServletOutputStream for writing binary data
Throws:: java.lang.IllegalStateException - if the getWriter method has been called on this response; java.io.IOException - if an input or output exception occurred
See Also:: getWriter()

getWriter


public java.io.PrintWriter getWriter()
                              throws java.io.IOException

Returns a PrintWriter object that can send character text to the client. The character encoding used is the one specified in the charset= property of the setContentType(java.lang.String) method, which must be called before calling this method for the charset to take effect.

If necessary, the MIME type of the response is modified to reflect the character encoding used.

Calling flush() on the PrintWriter commits the response.

Either this method or getOutputStream() may be called to write the body, not both.

Returns:: a PrintWriter object that can return character data to the client
Throws:: java.io.UnsupportedEncodingException - if the charset specified in setContentType cannot be used; java.lang.IllegalStateException - if the getOutputStream method has already been called for this response object; java.io.IOException - if an input or output exception occurred
See Also:: getOutputStream(), setContentType(java.lang.String)

setContentLength


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.

Parameters:: len - an integer specifying the length of the content being returned to the client; sets the Content-Length header

setContentType


public void setContentType(java.lang.String type)

Sets the content type of the response being sent to the client. The content type may include the type of character encoding used, for example, text/html; charset=ISO-8859-4.

If obtaining a PrintWriter, this method should be called first.

Parameters:: type - a String specifying the MIME type of the content
See Also:: getOutputStream(), getWriter()

setBufferSize


public void setBufferSize(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, this method throws an IllegalStateException.

Parameters:: size - the preferred buffer size
Throws:: java.lang.IllegalStateException - if this method is called after content has been written
See Also:: getBufferSize(), flushBuffer(), isCommitted(), reset()

getBufferSize


public int getBufferSize()

Returns the actual buffer size used for the response. If no buffering is used, this method returns 0.

Returns:: the actual buffer size used
See Also:: setBufferSize(int), flushBuffer(), isCommitted(), reset()

flushBuffer


public void flushBuffer()
                 throws java.io.IOException

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.

java.io.IOException
See Also:: setBufferSize(int), getBufferSize(), isCommitted(), reset()

resetBuffer


public void resetBuffer()

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.

Since:: 2.3

isCommitted


public boolean isCommitted()

Returns a boolean indicating if the response has been committed. A commited response has already had its status code and headers written.

Returns:: a boolean indicating if the response has been committed
See Also:: setBufferSize(int), getBufferSize(), flushBuffer(), reset()

reset


public void reset()

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:: java.lang.IllegalStateException - if the response has already been committed
See Also:: setBufferSize(int), getBufferSize(), flushBuffer(), isCommitted()

setLocale


public void setLocale(java.util.Locale loc)

Sets the locale of the response, setting the headers (including the Content-Type's charset) as appropriate. This method should be called before a call to getWriter(). By default, the response locale is the default locale for the server.

Parameters:: loc - the locale of the response
See Also:: getLocale()

getLocale


public java.util.Locale getLocale()

Returns the locale assigned to the response.

See Also:: setLocale(java.util.Locale)