Java tutorial
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.net.*; public class MyServlet extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setBufferSize(8 * 1024); // 8K buffer res.setContentType("text/html"); PrintWriter out = res.getWriter(); int size = res.getBufferSize(); // returns 8096 or greater // Record the default size, in the log log("The default buffer size is " + size); out.println("The client won't see this"); res.reset(); out.println("And this won't be seen if sendError() is called"); if (req.getParameter("important_parameter") == null) { res.sendError(res.SC_BAD_REQUEST, "important_parameter needed"); } } }