/* * @(#)KeepAliveServlet.java 1.3 97/05/22 * * Copyright (c) 1995-1997 Sun Microsystems, Inc. All Rights Reserved. * * This software is the confidential and proprietary information of Sun * Microsystems, Inc. ("Confidential Information"). You shall not * disclose such Confidential Information and shall use it only in * accordance with the terms of the license agreement you entered into * with Sun. * * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING * THIS SOFTWARE OR ITS DERIVATIVES. * * CopyrightVersion 1.0 */ import java.io.*; import javax.servlet.*; import javax.servlet.http.*; /** * This is an example of different ways to do keepalive connections * with servlets. The Content-Length header needs to be set for * keep-alive to work. This is done automatically for servlets with * small amounts of output (<4K), but needs to be done manually * otherwise. *

* What is keep-alive, and why should you care?
*

* When a browser talks to a server, it needs to establish a TCP connection. * Establishing this connection is expensive in terms of time. Keep-Alive * connections are connections which keep the connection open for subsequent * requests, greatly speeding the downloading of data from the server. * By ensuring that you follow the simple rules illustrated below, you * can enable automatic establishment of Keep-Alive connections from your * servlet. * * @author Jim Driscoll * @version 1.3 05/22/97 * */ public class KeepAliveServlet extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("text/html"); ServletOutputStream out = res.getOutputStream(); //Set up the strings we will use for output String str1 = " Keep-Alive Servlet Output"; str1 = str1 + "\r\n"; String str2 = "

Keep-Alive Servlet Output

\r\n"; String str3 = "

This is output from Keep-Alive Servlet.\r\n"; String str4 = "\r\n"; int strlen1 = str1.length(); int strlen2 = str2.length(); int strlen3 = str3.length(); int strlen4 = str4.length(); String runType = req.getParameter("runType"); if (runType == null ||runType.equals("short nohead")) {; // First the "normal" way - keepalive and content-length should // be automatically set out.print(str1); out.print(str2); out.print(str3); out.print(str4); out.close(); } else if (runType.equals("short nohead flush")) { // If you have a flush() of the output stream, // content length can't be determined - so, // keepalive will not be enabled! (Don't worry, // the output stream is flushed on close - you // won't lose any data) out.print(str1); out.print(str2); out.print(str3); out.flush(); out.print(str4); out.close(); } else if (runType.equals("long nohead")) { // This way tests a large body with no content-length specified // It will not, normally, have keepalive enabled // Note that the cut-off for automatic determination of // content-length is 4k bytes in JavaWebServer out.print(str1); out.print(str2); for (int i = 0; i < 100;i++) { out.println(str3); } out.print(str4); out.close(); } else if (runType.equals("short head")) { // This way manually sets the content-length, // keepalive should be on automatically res.setContentLength(strlen1+strlen2+strlen3+strlen4); out.print(str1); out.print(str2); out.print(str3); out.print(str4); out.close(); } else if (runType.equals("long head")) { // This way manually sets the content-length on long output, // which should cause keepalive to be enabled res.setContentLength(strlen1+strlen2+(strlen3*100)+strlen4); out.print(str1); out.print(str2); for (int i = 0; i < 100;i++) { out.print(str3); } out.print(str4); out.close(); } else { //Bogus value out.println(" Keep-Alive Servlet Output "); out.println("

Keep-Alive Servlet Output

"); out.println("

Bogus value set for querystring."); out.println("

Set the runType parameter to one of:."); out.println("short+nohead"); out.println("short+head"); out.println("long+nohead"); out.println("long+head"); out.println(""); out.close(); } } public String getServletInfo() { return "A servlet which demonstrates keep-alive programming"; } }