21.7 Java4570: session tracking using cookies  (Page 12/7)

Table of contents

• Preface
  • Viewing tip
    • Figures
    • Listings
• General background information
  • Program output
  • What are cookies?
  • The Java Cookie class
• Discussion and sample code
  • The servlet program
    • Interesting code fragments
  • The JSP program
• Run the programs
• 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 cookies, and to compare a servlet with a JSP to accomplish the same objective.

If you haven't already done so, I strongly recommend that you study Java4370: Cookies with JSP before continuing with this module. Dr. Martinez explains many aspects ofcookies in that module. Most of those aspects apply to both JSP and servlets and many of them won't be repeated in this module.

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 the servlet program.
• Figure 2 . Output from the JSP program.
• Figure 3 . Description of the Cookie constructor.

Listings

• Listing 1 . Beginning of the doGet method.
• Listing 2 . Construct a unique session ID.
• Listing 3 . Get all of the cookies into an array of type Cookie.
• Listing 4 . Get and save submitted value.
• Listing 5 . Create a new session ID cookie.
• Listing 6 . Create, name, and populate a new Cookie object.
• Listing 7 . Familiar code.
• Listing 8 . Get and display cookie names and values.
• Listing 9 . Display currently submitted field value.
• Listing 10 . The servlet program named Java4570a.java.
• Listing 11 . The JSP program named Java4570b.jsp.

General background information

Program output

I will explain a servlet program and present a comparable JSP program in this module. The purpose is to show you how to write servlets that use cookies for sessiontracking and to make it possible to compare a servlet and a JSP that both achieve the same objective.

The servlet output

Figure 1 shows the output produced by requesting the servlet from the localhost server using the Chrome browser and then submitting the names Tom,Dick, and Harry using the input text field and the submit button. I will refer back to this Figure later while explaining the servlet code.

Figure 1 - Output from the servlet program.

The JSP output

Figure 2 shows the output produced by requesting the JSP from the localhost server using the Firefox browser and then submitting the names Tom,Dick, and Harry using the input text field and the submit button. I will refer back to this Figure later while explaining the JSP code.

Figure 2 - Output from the JSP program.

(The main difference between Figure 1 and Figure 2 is the line that begins with JSESSIONID in Figure 2 . Also Figure 1 is displayed in a Chrome browser and Figure 2 is displayed in a Firefox browser.)