Groovy supports multiple ways to generate text dynamically including GStrings,
printf if you are using Java 5, and MarkupBuilder just to name a few. In addition to these, there is a dedicated template framework which is well-suited to applications where the text to be generated follows the form of a static template.
The template framework in Groovy consists of a TemplateEngine abstract base class that engines must implement and a Template interface that the resulting templates they generate must implement.
Included with Groovy are several template engines. Shown here is the SimpleTemplateEngine that allows you to use JSP-like scriptlets (see example below), script, and EL expressions in your template in order to generate parameterized text. Here is an example of using the system:
While it is generally not deemed good practice to mix processing logic in your template (or view), sometimes very simple logic can be useful. E.g. in the example above, we could change this:
to this (assuming we have set up a static import for capitalize):
Also just an advanced usage note. Because templates are created using two passes under the covers (pass one converts to script code, pass two runs the script to generate the output) you have to escape any backslashes. E.g. if we wanted quotes around The Big Apple above, we would use:
<% print city == "New York" ? "
"The Big Apple
"" : city %>
Similarly if we wanted a newline, we would use "
" in any GString or template processing code. A normal "
\n" is fine within the static template itself.
Groovy also supports a
GStringTemplateEngine (stores the template as writable closures) and
XmlTemplateEngine (works well when the template and output are valid XML).
You can also plug in other templating solutions, e.g. GFreeMarker, Velocity, StringTemplate and others.
Using TemplateServlet to serve single JSP-like HTML files
Here is a simple example helloworld.html file which is not validating and does not have a
head element. But it demonstrates, how to let Groovy compile and serve your HTML files to web clients. The tag syntax close to JSP and should be easy to read:
The first Groovy block - a for loop - spans the
HelloWorld! text. Guess what happens? And the second Groovy statement prints the servlet's session id - if there is a session avaiable. The variable
session is one of some default bound keys. More details reveals the documentation of
Here is some sample code using http://jetty.mortbay.orgs servlet container. With jetty6.0, copy jetty-6.1.3.jar and jetty-util-6.1.3.jar into $HOME/.groovy/lib, create a tiny web server with the following. To test it, add your above helloworld.html file into your current directory and browse http://localhost:1234/helloworld.html
Here is a similiar web.xml example.