HttpServletResponse

HttpServletResponse is an interface in the Java Servlet API that represents the HTTP response to be sent to a client. It is provided to servlet methods such as doGet and doPost by the servlet container, which uses it to construct and transmit the response. Implementations are supplied by the web server or container and control how the response is delivered.

The interface exposes methods to control status codes, headers, and the response body. Key operations include setStatus(int sc) and sendError(int sc) for signaling status or errors; sendRedirect(String location) for client redirection. Headers can be set or added with setHeader(String name, String value) and addHeader(String name, String value). Content type and encoding are configured with setContentType(String) and setCharacterEncoding(String). The response body can be produced via getOutputStream() for binary data or getWriter() for character data. Content length can be specified with setContentLength(int) or setContentLengthLong(long).

Additional controls include buffering via setBufferSize(int), flushBuffer(), and resetBuffer(); and state management with isCommitted() and reset(). Cookies can be added with addCookie(Cookie). Date and integer headers can be set with setDateHeader and setIntHeader. The interface also supports setLocale(Locale) to influence localization of the response.

HttpServletResponse is part of javax.servlet.http in older specifications and jakarta.servlet.http in newer ones; the exact package depends on the servlet API version used. In practice, the response object allows a servlet to construct the HTTP response before the data is returned to the client, with the container handling the details of network transmission.