Interface: javax.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 javax.servlet.ServletOutputStream returned by javax.servlet.ServletResponse.getOutputStream().
To send character data, use the PrintWriter object
returned by javax.servlet.ServletResponse.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 javax.servlet.ServletResponse.setCharacterEncoding(java.lang.String) and
javax.servlet.ServletResponse.setContentType(java.lang.String) methods, or implicitly
using the javax.servlet.ServletResponse.setLocale(java.util.Locale) 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.
Methods
-
flushBuffertop
public void flushBuffer() throws IOExceptionForces 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. -
getBufferSizetop
public int getBufferSize()Returns the actual buffer size used for the response. If no buffering is used, this method returns 0. -
getCharacterEncodingtop
public String getCharacterEncoding()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 javax.servlet.ServletResponse.setCharacterEncoding(java.lang.String) or javax.servlet.ServletResponse.setContentType(java.lang.String) methods, or implicitly using the javax.servlet.ServletResponse.setLocale(java.util.Locale) method. Explicit specifications take precedence over implicit specifications. Calls made to these methods aftergetWriterhas been called or after the response has been committed have no effect on the character encoding. If no character encoding has been specified,ISO-8859-1is returned.See RFC 2047 (http://www.ietf.org/rfc/rfc2047.txt) for more information about character encoding and MIME.
-
getContentTypetop
public String getContentType()Returns the content type used for the MIME body sent in this response. The content type proper must have been specified using javax.servlet.ServletResponse.setContentType(java.lang.String) 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 javax.servlet.ServletResponse.getCharacterEncoding() or javax.servlet.ServletResponse.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. -
getLocaletop
public Locale getLocale()Returns the locale specified for this response using the javax.servlet.ServletResponse.setLocale(java.util.Locale) method. Calls made tosetLocaleafter the response is committed have no effect. If no locale has been specified, the container's default locale is returned. -
getOutputStreamtop
public ServletOutputStream getOutputStream() throws IOExceptionReturns a javax.servlet.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 javax.servlet.ServletResponse.getWriter() may be called to write the body, not both.
-
getWritertop
public PrintWriter getWriter() throws IOExceptionReturns aPrintWriterobject that can send character text to the client. ThePrintWriteruses the character encoding returned by javax.servlet.ServletResponse.getCharacterEncoding(). If the response's character encoding has not been specified as described ingetCharacterEncoding(i.e., the method just returns the default valueISO-8859-1),getWriterupdates it toISO-8859-1.Calling flush() on the
PrintWritercommits the response.Either this method or javax.servlet.ServletResponse.getOutputStream() may be called to write the body, not both.
-
isCommittedtop
public boolean isCommitted()Returns a boolean indicating if the response has been committed. A committed response has already had its status code and headers written. -
resettop
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 anIllegalStateException. -
resetBuffertop
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 anIllegalStateException. -
setBufferSizetop
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 usinggetBufferSize.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. -
setCharacterEncodingtop
public 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 javax.servlet.ServletResponse.setContentType(java.lang.String) or javax.servlet.ServletResponse.setLocale(java.util.Locale), this method overrides it. Calling javax.servlet.ServletResponse.setContentType(java.lang.String) with theStringoftext/htmland calling this method with theStringofUTF-8is equivalent with callingsetContentTypewith theStringoftext/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
getWriterhas 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-Typeheader 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. -
setContentLengthtop
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. -
setContentTypetop
public void setContentType(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 beforegetWriteris 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
getWriterhas 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-Typeheader is used. -
setLocaletop
public void setLocale(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 javax.servlet.ServletResponse.setContentType(java.lang.String) or javax.servlet.ServletResponse.setCharacterEncoding(java.lang.String),getWriterhasn't been called yet, and the response hasn't been committed yet. If the deployment descriptor contains alocale-encoding-mapping-listelement, 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 javax.servlet.ServletResponse.setContentType(java.lang.String) has been called with a charset specification, after javax.servlet.ServletResponse.setCharacterEncoding(java.lang.String) has been called, after
getWriterhas 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-Languageheader, the character encoding as part of theContent-Typeheader 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.