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

ErrorReportValve


This valve is used to post-process the generated response, and so will fire only after the basic valve has finished its processing. This is possible because its invoke() method delegates to the remainder of the pipeline before actually doing any processing for itself.

If the response has already been committed, this valve does nothing more. This would be the case when a custom error resource has been found by the StandardHostValve for a Throwable or for a response status code and has been successfully dispatched using a RequestDispatcher.

However, if the response has not yet been handled, this valve will provide the default handling behavior.

If there is a javax.servlet.error.exception attribute on the request, then it marks this as an error response, and invokes response.sendError() with an internal server error (500) status code.

It then retrieves the response's message, filters it, and generates the HTML for a default error page.

Note

You can have the ErrorReportValve generate...