Groovlets

You can write normal Java servlets in Groovy (i.e. Groovlets).
There is also a GroovyServlet which automatically compile your .groovy source files, turn them into bytecode, load the Class and cache it until you change the source file.

Here's a simple example to show you the kind of thing you can do from a Groovlet.
Notice the use of implicit variables to access the session, output & request.

Error rendering macro 'code' : Invalid value specified for parameter lang

Or, do the same thing using MarkupBuilder:

Error rendering macro 'code' : Invalid value specified for parameter lang

Implicit variables

The following variables are ready for use in Groovlets:

variable name	bound to	note
request	ServletRequest
response	ServletResponse
context	ServletContext
application	ServletContext	unlike Struts
session	getSession(false)	can be null! (**)
out	response.getWriter()	see below
sout	response.getOutputStream()	see below
html	new MarkupBuilder(out)	see below

These variables cannot be reassigned inside a Groovlet.
They are bound on first access, allowing to e.g. calling
methods on the 'response' object before using 'out'.

(**) The session variable is only set, if there was already
a session object. See the 'if (session == null)' checks in
the examples above.

Setting up groovylets

Put the following in your web.xml:

Then all the groovy jar files into WEB-INF/lib. You should only need to put the groovy.jar, the antlr.jar and the asm.jar. Or copy the groovy-all-xyz.jar into WEB-INF/lib - this almost all jar contains the antlr and asm jars.

Now put the .groovy files in, say, the root directory (i.e. where you would put your html files). The groovy servlet takes care of compiling the .groovy files.

So for example using tomcat you could edit tomcat/conf/server.xml like so:

Then access it with http://localhost:8080/groovy/hello.groovy