Book Image

Tomcat 6 Developer's Guide

Book Image

Tomcat 6 Developer's Guide

Overview of this book

While Tomcat is one of the most popular servlet containers, its inner workings still remain a mystery to many developers. If you only have a superficial familiarity of how this container actually functions, much of its power remains untapped and underutilized. This book will provide you with all that you need to undertand how to effectively use Apache Tomcat. This book begins by providing detailed instructions on building a Tomcat distribution. The next few chapters introduce you to the conceptual underpinnings of web servers, the Java EE and servlet specifications, and the Tomcat container. Subsequent chapters address the key Tomcat components, taking care to provide you with the information needed to understand the internal workings of each component. Detailed examples let you walk through a Tomcat installation, stepping into key Tomcat components, as well as into your own custom servlets. During the course of the book you will encounter various structural components such as the Server and Service; containers such as the Engine, Host, Context, and Wrapper; and helpers such as the Loader, Manager, and Valve. You will also see how Tomcat implements the JNDI API to provide both a directory service for storage agnostic access to its resources, as well as a naming service that implements the Java EE Environment Naming Context. Along the way you will learn how various elements of the servlet 2.5 specification, as well as the HTTP RFCs are implemented by a servlet container. By the end of your journey, you will be able to count yourself as part of the elite minority of Java EE web developers who truly understand what goes on under the covers of a servlet container.
Table of Contents (17 chapters)
Tomcat 6 Developer's Guide
Credits
About the author
Acknowledgement
About the reviewers
Preface

Session propagation mechanisms


Before we dive into the implementations of the session and its manager, let's address the issue of how the identifier is returned by the client to the server.

As was stated above, the server generates a unique identifier for the conversational state holder for a client and communicates this identifier to the client.

Statefulness will only work if the client returns that identifier back to the server, for each request that is part of that conversation.

When each new request is received, a server attempts to locate this identifier, and use it to look up the conversational state associated with this client.

If a request comes without this identifier, the server has no way of recognizing that client, and so it treats the request as having come from a brand new client.

There are two common mechanisms that are used to ensure that the session identifier is communicated across each interaction between the client and the server—cookies and URL rewriting.

Cookies

When using...