21.9 Java4580: session tracking using the session tracking api  (Page 12/9)

Table of contents

• Preface
  • Viewing tip
    • Figures
    • Listings
• General background information
  • Introduction
  • Program output
  • The HttpSession Interface
• Discussion and sample code
• Run the program
• Miscellaneous
• Complete program listing

Preface

This module is one in a collection of modules designed for teaching INEW 2338 Advanced Java (Web) at Austin Community College in Austin, TX. The purpose of this module is to explainsession tracking using a servlet and the session tracking API .

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figures and Listings while you are reading about them.

Figures

• Figure 1 . Output from access #1.
• Figure 2 . Output from access #2.
• Figure 3 . Output from access #3.
• Figure 4 . Output from access #4.
• Figure 5 . Output from access #5.
• Figure 6 . Output from access #6.
• Figure 7 . Output from access #7.

Listings

• Listing 1 . Beginning of the doGet method.
• Listing 2 . Get the session object.
• Listing 3 . Get an output stream.
• Listing 4 . A hit counter.
• Listing 5 . Insert a Date object into the session.
• Listing 6 . An object of type MyClass.
• Listing 7 . Display information about the session.
• Listing 8 . Display information about the objects.
• Listing 9 . The inner class named MyClass.
• Listing 10 . The servlet named Java4580a.java.

General background information

Introduction

This is the fourth in a series of modules designed to show you how to implement session tracking using servlets. As mentioned earlier, the purpose of this module is to illustrate session tracking using the session tracking API .

Earlier modules have illustrated three different ways to implement session tracking with servlets

• hidden fields
• URL rewriting
• cookies

A higher-level approach to session tracking

The servlet programs in those earlier modules were written at a fairly low level. The session tracking API allows you to program at a somewhat higher level. Before you get too excited, however,be aware that this may or may not be the answer to your needs. In some cases, depending on the server involved, you may find that the session tracking APIrelies exclusively on cookies. If that is the case with your server and if your clients don't allow cookies, then the API may not meet your needs. Youmay find yourself back at square one -- hidden fields or URL rewriting .

The HttpSession interface

The capability that I have referred to as the session tracking API is primarily based on the HttpSession interface that I will discuss later. It alsoincludes some other interfaces and classes as well.

Program output

Figure 1 through Figure 7 show the output produced by the servlet named Java4580a for each of the first seven times it is accessed by the same browser. You might just want to glance over these Figures now. I willrefer back to them and explain their meaning throughout the discussion of the servlet.

Figure 1 - Output from access #1.

Figure 2 - Output from access #2.