Ajax on Java

Chapter 5. Getting Useful Data

Google Suggest was one of the first Ajax applications: it’s actually older than the name Ajax. Google Suggest alters the experience of filling in an HTML form. Normally, you fill in your data, click Submit, and cross your fingers; more than likely, you’ll find out that you’ve requested a username that already exists, made a typo in your area code, or made some other simple error that you have to correct. Google Suggest changes all that: as you type in a field, it continuously shows you possible completions that match entries in the database.

Form Entry with Ajax

Order-entry applications aren’t sexy, but they’re everywhere—and Ajax could be one of the best things that’s ever happened to them. In the world of web applications, it’s all about ease of use and saving time. Google Suggest suggests a way of making the web experience much easier: using Suggest as a model, we can write web applications that tell users immediately when they have requested usernames that are already in use, that fill in a city and state automatically on the basis of a zip code, and that make it simpler to enter names (product names, customer names, etc.) that are already in the database.

That’s what we’ll do in this chapter, while exploring ways to make a signup page easier to use and manage. We’ll start with a Customer Sign-up page, shown in Figure 5-1. This page has two fields that get special treatment: the username field and the zip code field. We’ll call these fields suggestion ...