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

StandardWrapper


This image depicts some key aspects of the org.apache.catalina.core.StandardWrapper component. As shown, this component extends ContainerBase, marking it as a container. However, a wrapper exists at the lowest level of the container hierarchy, and any attempt to add a child to it will be met with scorn, and an IllegalStateException.

As the web.xml deployment descriptor is parsed, any<servlet> elements within it are converted into StandardWrapper instances and are added as children of the context.

Key members of the StandardWrapper instance include the following:

  • a mappings ArrayList which represents the collection of<servlet-mappings> elements in the web.xml file that are associated with this servlet

  • a parameters HashMap which holds the servlet's initialization parameters

  • a servletClass member that holds the implementation class for the servlet

  • a loadOnStartup integer which indicates whether this servlet should be loaded and initialized at context startup.

T...