Listing 9 - Listing 9.1 ShowSession.java package...

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Unformatted text preview: Listing 9.1 ShowSession.java package coreservlets; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; /** Servlet that uses session tracking to keep per-client * access counts. Also shows other info about the session. */ public class ShowSession extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); HttpSession session = request.getSession(); String heading; Integer accessCount = (Integer)session.getAttribute("accessCount"); if (accessCount == null) { accessCount = new Integer(0); heading = "Welcome, Newcomer"; } else { heading = "Welcome Back"; accessCount = new Integer(accessCount.intValue() + 1); } // Integer is an immutable data structure. So, you // cannot modify the old one in-place. Instead, you // have to allocate a new one and redo setAttribute. session.setAttribute("accessCount", accessCount); PrintWriter out = response.getWriter(); String title = "Session Tracking Example"; String docType = "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " + "Transitional//EN\">\n"; out.println(docType + "<HTML>\n" + "<HEAD><TITLE>" + title + "</TITLE></HEAD>\n" + "<BODY BGCOLOR=\"#FDF5E6\">\n" + "<CENTER>\n" + "<H1>" + heading + "</H1>\n" + "<H2>Information on Your Session:</H2>\n" + "<TABLE BORDER=1>\n" + "<TR BGCOLOR=\"#FFAD00\">\n" + " <TH>Info Type<TH>Value\n" + "<TR>\n" + " <TD>ID\n" + " <TD>" + session.getId() + "\n" + "<TR>\n" + " <TD>Creation Time\n" + " <TD>" + new Date(session.getCreationTime()) + "\n" + "<TR>\n" + " <TD>Time of Last Access\n" + " <TD>" + new Date(session.getLastAccessedTime()) + "\n" + "<TR>\n" + " <TD>Number of Previous Accesses\n" + " <TD>" + accessCount + "\n" + "</TABLE>\n" + "</CENTER></BODY></HTML>"); } } Listing 9.2 ShowItems.java package coreservlets; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; /** Servlet that displays a list of items being ordered. * Accumulates them in an ArrayList with no attempt at * detecting repeated items. Used to demonstrate basic * session tracking. */ public class ShowItems extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); ArrayList previousItems = (ArrayList)session.getAttribute("previousItems"); if (previousItems == null) { previousItems = new ArrayList(); session.setAttribute("previousItems", previousItems); } String newItem = request.getParameter("newItem"); response.setContentType("text/html"); PrintWriter out = response.getWriter(); String title = "Items Purchased"; String docType = "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " + "Transitional//EN\">\n"; out.println(docType + "<HTML>\n" + "<HEAD><TITLE>" + title + "</TITLE></HEAD>\n" + "<BODY BGCOLOR=\"#FDF5E6\">\n" + "<H1>" + title + "</H1>"); synchronized(previousItems) { if (newItem != null) { previousItems.add(newItem);previousItems....
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Listing 9 - Listing 9.1 ShowSession.java package...

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