Practically Groovy: Go Server-Side Up, with Groovy
By Andrew Glover2005-05-05
The Groovlet, Please
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Writing Groovlets is indubitably simple, since Groovy poses few requirements in terms of class hierarchy extensions. With Groovlets, there is no need to extend from javax.servlet.http.HttpServlet, javax.servlet.GenericServlet, or some slick GroovyServlet class. In fact, creating a Groovlet is as simple as creating a Groovy script. You don't even have to create a class. In Listing 5, I've written a simple Groovlet that does two things: It prints some HTML, then it provides some information about the container it's running in.
Listing 5. Getting started with Groovlets
println """If you viewed this Groovlet in your browser, it would look something like what you see in Figure 1.
<html><head>
<title>Groovlets 101</title>
</head>
<body>
<p>
Welcome to Groovlets 101. As you can see
this Groovlet is fairly simple.
</p>
<p>
This course is being run on the following servlet container: </br>
${application.getServerInfo()}
</p>
</body>
</html>
"""
Figure 1. Output from the simple Groovlet
Looking closely at the Groovlet in Listing 5 should take you back to the time when you first started writing Groovy scripts. First, there is no main method or class definition, just some simple code. What's more, the Groovlet framework implicitly provides instance variables, such as ServletRequest, ServletResponse, ServletContext, and HttpSession. See how I was able to reference the instance of ServletContext via the application variable? If I wanted to grab the instance of HttpSession, I'd use the session variable name. Similarly, I can use request and response for ServletRequest and ServletResponse, respectively.
Tutorial Pages:
» On-the-fly Server-Side Programming with Groovlets and GSPs
» Defining Functions in Scripts
» Groovlets and GSPs
» The Groovlet, Please
» A Diagnostic Groovlet
» What About Those GSPs?
» Refactor me this ...
» Conclusion
» Resources
First published by IBM DeveloperWorks
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