Book Image

Learning Jakarta Struts 1.2: a concise and practical tutorial

By : Stephan Wiesner
Book Image

Learning Jakarta Struts 1.2: a concise and practical tutorial

By: Stephan Wiesner

Overview of this book

<p>Jakarta Struts is an Open Source Java framework for developing web applications. By cleanly separating logic and presentation, Struts makes applications more manageable and maintainable.<br />Since its donation to the Apache Foundation&nbsp; in 2001, Struts has been rapidly accepted as the leading Java web application framework, and community support and development is well established.<br /><br />Struts-based web sites are built from the ground up to be easily modifiable and maintainable, and internationalization and flexibility of design are deeply rooted. Struts uses the Model-View-Controller design pattern to enforce a strict separation between processing logic and presentation logic, and enables efficient object re-use.<br /><br />The book is written as a structured tutorial, with each chapter building on the last. The book begins by introducing the architecture of a Struts application in terms of the Model-View-Controller pattern. Having explained how to install Jakarta and Struts, the book then goes straight into an initial implementation of the book store. The well structured code of the book store application is explained and related simply to the architectural issues.<br /><br />Custom Actions, internationalization and the possibilities offered by Taglibs are covered early to illustrate the power and flexibility inherent in the framework. The bookstore application is then enhanced in functionality and quality through the addition of logging and configuration data, and well-crafted forms. At each stage of enhancement, the design issues are laid out succinctly, then the practical implementation explained clearly. This combination of theory and practical example lays a solid understanding of both the principles and the practice of building Struts applications.</p>
Table of Contents (20 chapters)
Learning Jakarta Struts 1.2
Credits
Preface
About the Book
Glossary
Literature

11.1 Verifying User Input with the Struts Validator


The implementation with three classes for each form, Book, BookForm, and BookAction, which we have used up until now, is relatively time-consuming. DynaForms help to lift the load somewhat, but there is still plenty of work left to do, which can be especially awkward for repetitive tasks that are boring and therefore error-prone.

The Validator, developed by David Winterfeldt, uses an XML file to contain the validation rules. The Validator can also generate JavaScript that can be used to provide client‑side verification. Its ability to use regular expressions in the validation rules is particularly helpful.

One disadvantage, as with many things in Struts, is that the Validator requires the context to be reloaded after every modification. This can make debugging difficult as any actions taken up to that point must be performed again.

Since Struts 1.1, the Validator and all the required JAR files have been packaged with the Struts download (in...