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Professional Java for Web Applications by Nicholas S. Williams

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Chapter 5Maintaining State Using Sessions

  • Why sessions are necessary
  • Working with cookies and URL parameters
  • How to store data in a session
  • Making sessions useful
  • How to cluster an application that uses sessions

WROX.COM CODE DOWNLOADS FOR THIS CHAPTER

You can find the wrox.com code downloads for this chapter at www.wrox.com/go/projavaforwebapps on the Download Code tab. The code for this chapter is divided into the following major examples:

  • Shopping-Cart Project
  • Session-Activity Project
  • Customer-Support-v3 Project

NEW MAVEN DEPENDENCIES FOR THIS CHAPTER

There are no new Maven dependencies for this chapter. Continue to use the Maven dependencies introduced in all previous chapters.

UNDERSTANDING WHY SESSIONS ARE NECESSARY

So far you’ve learned about web applications, web containers, Servlets, JSPs, and how Servlets and JSPs work together. You have also learned about the life cycle of a request, and it should be clear at this point that the tools you have been introduced to so far do not enable you to associate multiple requests coming from the same client and share data between those requests. You might think that you can use the IP address as a unique identifier and all requests from an IP address within some timeframe must belong to the same client. Unfortunately, due to Network Address Translation (NAT) this is not reliable. Thousands of students at a college campus can literally all use the same IP address, hidden behind a NAT router. For this reason ...

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