"State" is a central concern of all sorts of distributed applications, but especially of Web applications, as HTTP and its derivatives are intrinsically stateless. Clear thinking about how data persists across retrievals, sessions, processes, and other boundaries can help you improve your Web applications, both present and future.

In the first part of this series, you saw how to generate JavaScript code for sending Ajax requests and processing Ajax responses. The second part showed how to create HTML forms, using conventions and JSP tag files to minimize setup and configuration. In this third part of the series, you'll learn how to develop client-side validators based on JavaScript as well as server-side validators, which are implemented as JSP tag files backing up their JavaScript counterparts. You'll also learn how to use resource-bundles that are reloaded automatically when changed, without requiring the restart of the application.

Today's Web applications provide many benefits for online storage, access, and collaboration. Although some applications offer encryption of user data, most do not. This article provides tools and code needed to add basic encryption support for user data in one of the most popular online calendar applications. Building on the incredible flexibility of Firefox extensions and the Gnu Privacy Guard, this article shows you how to store only encrypted event descriptions in Google's Calendar application, while displaying a plain text version to anyone with the appropriate decryption keys.

Traditional Ajax development continues to be the leading method for producing rich Internet applications (RIAs). However, the popularity of Adobe Flex cannot be ignored. This article introduces the Adobe Flex Ajax Bridge (FABridge), a code library that enables an easy and consistent method for integrating Ajax and Flex content. By the end of this article, you'll be able to take advantage of the rich features available through Flash assets.

In this Mastering Grails installment, Scott Davis explores the various ways that Grails can use database tables that don't conform to the Grails naming standard. If you have Java classes that already map to your legacy databases, Grails allows you to use them unchanged. You'll see examples that use Hibernate HBM files and Enterprise JavaBeans 3 annotations with legacy Java classes.

The iPhone and iPod touch made Mobile Safari the most popular mobile browser in the United States. Although Mobile Safari is more than adequate at rendering normal Web pages, many Web developers created versions of applications aimed at the iPhone. Here in Part 3 of this "Developing iPhone applications using Ruby on Rails and Eclipse" series, we learn what you should do when the user reaches the end of the list structure and your application actually needs to display some content

The iPhone and iPod touch made Mobile Safari the most popular mobile browser in the United States. Although Mobile Safari is more than adequate at rendering normal Web pages, many Web developers created versions of applications aimed at the iPhone. Here in Part 2 of this "Developing iPhone applications using Ruby on Rails and Eclipse" series, we learn the common use of drill-down lists as a navigation method

You've seen reader comments on weblogs and other Web 2.0 sites, but the Atom protocol makes it possible to create and manage such comments in a very flexible way. Flexible Web annotations is an idea that will open up an entirely new class of Web applications with very little actual new invention. Learn how to create a system to manage annotations for anything on the Web, from nearly anywhere.

Ajax techniques have changed the face of large, commercial Web applications, but many smaller Web sites don't have the resources to rebuild their entire user interface overnight. New features should justify their costs by solving real-world interface problems and improving user experience. This series is teaching you to modernize your user interface incrementally using open source, client-side libraries. In this installment, you learn to turn slow, messy, annoying product-details pages into fast, elegant ones using DHTML and Ajax. You do so using the principle of progressive enhancement, ensuring that your site remains accessible to all sorts of user-agents.

Google Calendar allows Web application developers to access user-generated content and event information through its REST-based Developer API. PHP's SimpleXML extension and Zend's GData Library are ideal for processing the XML feeds generated by this API and using them to build customized PHP applications. This article introduces the Google Calendar Data API, demonstrates how you can use it to browse user-generated calendars; add and update calendar events; and perform keyword searches.

Ext JS is a powerful JavaScript library that simplifies Asynchronous JavaScript + XML (Ajax) development through the use of reusable objects and widgets. This article introduces Ext JS, providing an overview of the object-oriented JavaScript design concepts behind it, and shows how to use the Ext JS framework for rich Internet application UI elements.

Are you building a Web application? Is it supposed to look more like cragislist or flickr? If the answer is the former, then you can probably skip this article. Still reading? Well you are in luck. In this article, Part 2 of a three-part series on JavaScript libraries, you will see how to use the Scriptaculous JavaScript library to enhance your Web applications.

Detect intrusions, and prevent attacks from ruining your Web designs and application programming using Snort, a free and open source Network Intrusion Prevention System (NIPS) and Network Intrusion Detection System (NIDS) tool. In the first article in this series, you installed Snort and made sure it could detect packets, log traffic, and be prepared to detect intrusions. In this article, learn what the data inside those packets means, and how you can use that data to infer whether attacks are occurring and alert system administrators to those attacks.

Dodge common Web 2.0-based application attacks, such as cross-site scripting, and dramatically increase your Project Zero application's security using Active Content Filtering (ACF). ACF is a resolvable component within Project Zero that provides a library that can remove active content from request data (such as request parameters) and response output being sent to the client. Learn about the powerful capabilities of applying ACF to a Project Zero environment in which active content might exist.

Maybe you're trying to keep track of the traffic waiting for you on the commute home, or perhaps you're tracking the objects and people floating around Second Life or another virtual world. Wouldn't it be nice if you could track that kind of thing right from your browser? This tutorial shows you how to use Ajax to create an animated, self-updating radar screen.

The number of cell phone users worldwide is at 3.3 billion and rising, and Internet access from mobile phones is on a rapidly upward trajectory. Developing for the mobile Web has its unique demands. In this Mastering Grails installment, Scott Davis shows you how to make your Grails applications mobile phone friendly.

Mozilla Firefox 3 is a major release with many enhancements, some of which are targeted at users, and some at developers. One of the most interesting updates gives Web developers the ability to build Web applications that work even when the user is disconnected from the Internet. Use this article to learn more about these new Firefox 3 features, especially the new offline application support.

Access-control based security of application resources is one of the core features of Project Zero. With the goal of radical simplification in mind, the developers of Project Zero Security have made an effort to simplify the enablement of security and make it quick and easy. Learn about Project Zero Security and how to create a user registry, define security rules for the application, and leverage the two most common types of authentication -- basic and form-based. By the end of this article, you will have all the tools you need to build security into your Project Zero applications.

In this article, learn to use Dojo and Ajax to develop reusable components that can easily be integrated with core applications. A a step-by-step example shows how to develop a Web application that adds mailing capabilities to an existing blogging application, generates mailing widgets, and handles intricacies of cross domain communication.

The Ruby Java Bridge (RJB) lets you load Java classes directly to, and call them from, Ruby on Rails applications. This tutorial shows how you can put this toolkit to work by reusing your legacy Java Web application code in a modern Web development platform.