Dynamic Interaction With Your Web Application

Imagine you are working on a web application. A collection of servlets, HTML pages, classes, .jars, and other resources is now shaping into a fully complete application running on a web server. But something is just not right. Perhaps you are trying to investigate why certain forms seem to submit correctly but the database is not updating, or perhaps a generated web page reports that the server is in a state you would bet it cannot be in. Whatever the problem, you know you could gather a better understanding if only you could have access to the running servlet and check the current state of a few objects. Perhaps you could even temporarily fix it while you're at it.

In this article I will show you the code of a simple servlet. This servlet accepts just one attribute via the POST method. An equally simple HTML page consisting of a text area and a submit button is written to interact with it. Yet despite the simplicity of these two components, what we will have is a powerful tool to interactively analyze the state of any web application.