Maintaining State Using Sessions in our JEE 8 Web App Module

Jakarta Servlet Specification - Sessions

We will now add a Session Activity Example in order to learn more about Session Management.

It has the same index.jsp and base.jspf file as our previous example but implements a different re-direct

Maintaining State Using Sessions Part 2 Branch

1. Storing more Complex data in Session

You can store any class object in the Session however to satisfy requirements for clustering your web servers and deploying to cloud platforms the class needs to implement Serializable.

We use the PageVisit Class to store our session

public class PageVisit implements Serializable
{
  private long enteredTimestamp; //Allow for null value

 private Long leftTimestamp;

 private String request;

 private InetAddress ipAddress;  }	

We use the ActivityServlet Class to update our session

@WebServlet(
    name = "activitySessionServlet",
    urlPatterns = "/activitySession"
)
public class ActivityServlet extends HttpServlet {
    private static final long serialVersionUID = -6775967155118931064L;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.recordSessionActivity(request);

        this.viewSessionActivity(request, response);
    }

    private void recordSessionActivity(HttpServletRequest request) {
        HttpSession session = request.getSession();

        if (session.getAttribute("activity") == null)
            session.setAttribute("activity", new ArrayList<PageVisit>());

        @SuppressWarnings("unchecked")
        List<PageVisit> visits =
                (List<PageVisit>) session.getAttribute("activity");

        if (!visits.isEmpty()) {
            PageVisit last = visits.get(visits.size() - 1);
            last.setLeftTimestamp(System.currentTimeMillis());
        }

        PageVisit now = new PageVisit();
        now.setEnteredTimestamp(System.currentTimeMillis());
        if (request.getQueryString() == null)
            now.setRequest(request.getRequestURL().toString());
        else
            now.setRequest(request.getRequestURL() + "?" + request.getQueryString());
        try {
            now.setIpAddress(InetAddress.getByName(request.getRemoteAddr()));
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
        visits.add(now);
    }

    private void viewSessionActivity(HttpServletRequest request,
                                     HttpServletResponse response)
            throws ServletException, IOException {
        request.getRequestDispatcher("/WEB-INF/jsp/view/viewSessionActivity.jsp")
                .forward(request, response);
    }
}

We use the viewSessionActivity.jsp to display our session

<%@ page import="java.util.Vector, com.nicordesigns.PageVisit, java.util.Date" %>
<%@ page import="java.text.SimpleDateFormat" %>
<%!
    private static String toString(long timeInterval)
    {
        if(timeInterval < 1_000)
            return "less than one second";
        if(timeInterval < 60_000)
            return (timeInterval / 1_000) + " seconds";
        return "about " + (timeInterval / 60_000) + " minutes";
    }
%>
<%
    SimpleDateFormat f = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss Z");
%>
<!DOCTYPE html>
<html>
    <head>
        <title>Session Activity Tracker</title>
    </head>
    <body>
        <h2>Session Properties</h2>
        Session ID: <%= session.getId() %><br />
        Session is new: <%= session.isNew() %><br />
        Session created: <%= f.format(new Date(session.getCreationTime()))%><br />

        <h2>Page Activity This Session</h2>
        <%
            @SuppressWarnings("unchecked")
            Vector<PageVisit> visits =
                    (Vector<PageVisit>)session.getAttribute("activity");

            for(PageVisit visit : visits)
            {
                out.print(visit.getRequest());
                if(visit.getIpAddress() != null)
                    out.print(" from IP " + visit.getIpAddress().getHostAddress());
                out.print(" (" + f.format(new Date(visit.getEnteredTimestamp())));
                if(visit.getLeftTimestamp() != null)
                {
                    out.print(", stayed for " + toString(
                            visit.getLeftTimestamp() - visit.getEnteredTimestamp()
                    ));
                }
                out.println(")<br />");
            }
        %>
    </body>
</html>

2. Compiling, testing and debugging our session-activity web application

We will demonstrate that different browsers each get assigned a different session id and associated session object by running our sample session object.

JakartaJEEWebDevelopment

Jakarta JEE8 Enterprise Web Development