Head First Servlets and JSP, 2nd Edition.pdf

Head First Servlets and JSP™

Second Edition

by Bryan Basham, Kathy Sierra, and Bert Bates

Printed in the United States of America.

Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472.

O’Reilly Media books may be purchased for educational, business, or sales promotional use. Online editions are

also available for most titles ( safari.oreilly.com ). For more information, contact our corporate/institutional sales

department: (800) 998-9938 or corporate@oreilly.com .

Series Creators:

Kathy Sierra, Bert Bates

Series Editor:

Brett D. McLaughlin

Design Editor:

Louise Barr

Cover Designers:

Edie Freedman, Steve Fehler, Louise Barr

Production Editor:

Sanders Kleinfeld

Indexer:

Julie Hawks

Interior Decorators:

Kathy Sierra and Bert Bates

Servlet Wrangler:

Bryan Basham

Assistant to

the Front Controller:

Bert Bates

Printing History:

August 2004: First Edition.

March 2008: Second Edition.

The O’Reilly logo is a registered trademark of O’Reilly Media, Inc. The Head First series designations,

Head First Servlets and JSP™ , Second Edition, and related trade dress are trademarks of O’Reilly Media, Inc. Java

and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems,

Inc., in the United States and other countries. O’Reilly Media, Inc. is independent of Sun Microsystems.

Many of the designations used by manufacturers and sellers to distinguish their products are claimed as

trademarks. Where those designations appear in this book, and O’Reilly Media, Inc., was aware of a trademark

claim, the designations have been printed in caps or initial caps.

While every precaution has been taken in the preparation of this book, the publisher and the author assume no

responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.

In other words, if you use anything in Head First Servlets & JSP™ to, say, run a nuclear power plant or air

traffic control system, you’re on your own. Readers of this book should be advised that the authors hope

you remember them, should you create a huge, successful dotcom as a result of reading this book. We’ll

take stock options, beer, or dark chocolate

ISBN: 978-0-596-51668-0

[M]

table of contents

Table of Contents (Summary)

Intro

xix

Why use Servlets & JSPs: an introduction

Web App Architecture: high-level overview

Mini MVC Tutorial: hands-on MVC

Being a Servlet: request AND response

Being a Web App: attributes and listeners

147

Conversational state: session management

223

Being a JSP: using JSP

281

Script-free pages: scriptless JSP

343

Custom tags are powerful: using JSTL

439

When even JSTL is not enough: c ustom tag development

499

Deploying your web app: web app deployment

601

Keep it secret, keep it safe: web app security

649

The Power of Filters: wrappers and filters

701

Enterprise design patterns: patterns and struts

737

Appendix A: Final Mock Exam

791

Index

865

Table of Contents (the real thing)

Intro

Your brain on Servlets. Here you are trying to learn something, while here

your brain is doing you a favor by making sure the learning doesn’t stick . Your brain’s

thinking, “Better leave room for more important things, like which wild animals to avoid

and whether naked snowboarding is a bad idea.” So how do you trick your brain into

thinking that your life depends on knowing Servlets?

Who is this book for?

We know what your brain is thinking

xxi

Metacognition

xxiii

Bend your brain into submission

What you need for this book

xxvi

Passing the certification exam

xxviii

Technical reviewers

xxx

Acknowledgments

xxxi

table of contents

Why use Servlets & JSPs

Web applications are hot. How many GUI apps do you know that are used by

millions of users worldwide? As a web app developer, you can free yourself from the grip

of deployment problems all standalone apps have, and deliver your app to anyone with a

browser. But you need servlets and JSPs. Because plain old static HTML pages are so,

well, 1999. Learn to move from web site to web app .

Exam objectives

What web servers and clients do, and how they talk?

Two-minute guide to HTML

What is the HTTP protocol?

Anatomy of HTTP GET and POST requests and HTTP responses

Locating web pages using URLs

Web servers, static web pages, and CGI

Servlets Demystified: write, deploy, and run a servlet

JSP is what happened when somebody introduced Java to HTML

Web app architecture

Servlets need help. When a request comes in, somebody has to instantiate

the servlet or at least allocate a thread to handle the request. Somebody has to call the

servlet’s doPost() or doGet() method. Somebody has to get the request and the response

to the servlet. Somebody has to manage the life, death, and resources of the servlet. In

this chapter, we’ll look at the Container, and we’ll take a ﬁ rst look at the MVC pattern.

Exam Objectives

What is a Container and what does it give you?

How it looks in code (and what makes a servlet)

Naming servlets and mapping them to URLs using the DD

Story: Bob Builds a Matchmaking Site ( and MVC intro)

A Model-View-Controller (MVC) overview and example

A “working” Deployment Descriptor (DD)

How J2EE fits into all this

table of contents

Mini MVC tutorial

Create and deploy an MVC web app. It’s time to get your hands dirty

writing an HTML form, a servlet controller, a model (plain old Java class), an XML

deployment descriptor, and a JSP view. Time to build it, deploy it, and test it. But ﬁ rst, you

need to set up your development environment. Next, you need to set up your deployment

environment following the servlet and JSP specs and Tomcat requirements. True, this is a

small app... but there’s almost NO app that’s too small to use MVC.

Exam Objectives

Let’s build an MVC application; the first design

Create the development and deployment environments

Create and test the HTML for the initial form page

Create the Deployment Descriptor (DD)

Create, compile, deploy, and test the controller servlet

Design, build, and test the model component

Enhance the controller to call the model

Create and deploy the view component (it’s a JSP)

Enhance the controller servlet to call the JSP

Being a Servlet

Servlets need help. When a request A servlet’s job is to take a client’s request

and send back a response . The request might be simple: “ get me the Welcome page. ” Or

it might be complex: “ Complete my shopping cart check-out. ” The request carries crucial

data, and your servlet code has to know how to ﬁ nd it and how to use it. And your servlet

code has to know how to send a response . Or not ...

Exam Objectives

A servlet’s life in the Container

Servlet initialization and threads

101

A Servlet’s REAL job is to handle GET and POST requests.

105

The story of the non-idempotent request

112

What determines whether you get a GET or POST request?

117

Sending and using parameter(s)

119

So that’s the Request... now let’s see the Response

126

You can set response headers, you can add response headers

133

Servlet redirect vs. request dispatcher

136

Review: HttpServletResponse

140

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