Servlet. Web Server. Servlets are modules of Java code that run in web server. Internet Explorer. Servlet. Fire Fox. Servlet.

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Emory Snow
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1 Servlet OOS Lab

2 Servlet OOS Servlets are modules of Java code that run in web server. Internet Explorer Web Server Fire Fox Servlet Servlet Servlet Java Application 2

3 Servlet - Example OOS import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloClientServlet extends HttpServlet { protected void doget (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setcontenttype("text/html"); PrintWriter out = res.getwriter(); out.println("<html><head><title>hello Client!</TITLE>"+ "</HEAD><BODY>Hello Client!</BODY></HTML>"); out.close(); public String getservletinfo() { return SimpleServlet ; 3

4 Servlet For Dynamic Content OOS 4

5 Servlet For Dynamic Content OOS import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloClientServlet extends HttpServlet { protected void doget (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setcontenttype("text/html"); PrintWriter out = res.getwriter(); out.println("<html><head><title>hello Client!</TITLE>"+ "</HEAD><BODY>Hello Client!<P><HR> ) ; out.println( You are from + req.getremotehost() + : + req.getremoteport() + at + req.getrequesturl() ) ; out.println( </BODY></HTML>"); out.close(); public String getservletinfo() { return Simple Servlet with Dynamic Info. ; 5

6 Processing GET Request OOS GreetingServlet handles both pages 6

7 public class GreetingServlet extends HttpServlet { public void doget ( HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html"); response.setbuffersize(8192); PrintWriter out = response.getwriter(); out.println("<html>" + "<head><title>hello</title></head>"); out.println( "<body><img src=\"duke.waving.gif\" alt=\"duke waving\">" + "<h2>hello, my name is Duke. What's yours?</h2>" + "<form method=\"get\">" + "<input type=\"text\" name=\"username\" size=\"25\">" + "<p></p>" + "<input type=\"submit\" value=\"submit\">" + "<input type=\"reset\" value=\"reset\">" + "</form>"); String username = request.getparameter("username"); if ((username!= null) && (username.length() > 0)) { RequestDispatcher dispatcher = getservletcontext().getrequestdispatcher("/response"); if (dispatcher!= null) { dispatcher.include(request, response); out.println("</body></html>"); out.close(); public String getservletinfo() { return "The Hello servlet says hello.";

8 Form Processing Servlet OOS process form data manage persistent data use init parameters by Stefan Zeiger 8

9 import java.util.vector; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class ListManagerServlet extends HttpServlet { private Vector addresses; private String filename; public void init(servletconfig config) throws ServletException { super.init(config); filename = config.getinitparameter("addressfile"); try { WEB-INF\web.xml ObjectInputStream in = new ObjectInputStream(new FileInputStream(filename)); addresses = (Vector)in.readObject(); in.close(); catch(ioexception e) { addresses = new Vector(); catch(classnotfoundexception e) {addresses = new Vector();

10 protected void doget(httpservletrequest req, HttpServletResponse res) throws ServletException, IOException 37: { res.setcontenttype("text/html"); res.setheader("pragma", "no-cache"); PrintWriter out = res.getwriter(); out.print("<html><head><title>list Manager</TITLE></HEAD>"); out.print("<body><h3>members:</h3><ul>"); for(int i=0; i<addresses.size(); i++) out.print("<li>" + addresses.elementat(i)); out.print("</ul><hr><form METHOD=POST>"); out.print("enter your address: <INPUT TYPE=TEXT NAME= ><BR>"); out.print("<input TYPE=SUBMIT NAME=action VALUE=subscribe>"); out.print("<input TYPE=SUBMIT NAME=action VALUE=unsubscribe>"); out.print("</form></body></html>"); out.close();

11 protected void dopost (HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { String = req.getparameter(" "); String msg; if( == null) { res.senderror(res.sc_bad_request, "No address specified."); return; if(req.getparameter("action").equals("subscribe")) { if ( subscribe( ) ) msg = "Address " + + " has been subscribed."; else { res.senderror(res.sc_bad_request, "Address " + + " was already subscribed."); return; else { // unsubscribe is requested. if ( unsubscribe( ) ) msg = "Address " + + " has been removed."; else { res.senderror(res.sc_bad_request, "Address " + + " was not subscribed."); return; res.setcontenttype("text/html"); res.setheader("pragma", "no-cache"); PrintWriter out = res.getwriter(); out.print("<html><head><title>list Manager</TITLE></HEAD><BODY>"); out.print(msg); out.print("<hr><a HREF=\""); out.print(req.getrequesturi()); out.print("\">show the list</a></body></html>"); out.close(); public String getservletinfo() { return "ListManagerServlet 1.0 by Stefan Zeiger";

12 private synchronized boolean subscribe (String ) throws IOException { if ( addresses.contains( ) ) return false; addresses.addelement( ); save(); return true; private synchronized boolean unsubscribe (String ) throws IOException { if (!addresses.removeelement( ) ) return false; save(); return true; private void save() throws IOException { ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(filename)); out.writeobject(addresses); out.close();

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&' () - #-& -#-!& 2 - % (3 3 !!! + #%!%,)& ! # * +, ! "# # $! " &' ()!"#$$&$'(!!! ($) * + #!,)& - #-& +"- #!(-& #& #$.//0& -#-!& #-$$!& 1+#& 2-2" (3" 3 * * +, - -! #.// HttpServlet $ Servlet 2 $"!4)$5 #& 5 5 6! 0 -.// # 1 7 8 5 9 2 35-4 2 3+ -4 2 36-4 $