groovy/groovy-core — pull request #582 by uehaj (2015-01-01 07:59:22+00:00)
Title: TempateServlet requires default constroctor at TemplateEngine

TemplateServlet requires template engine which have default constructor to run.
If it is, you can use MarkupTempateEngine with http request through TemplateServlet without even single code.

template
groovy.servlet.TemplateServlet

template.engine
groovy.text.markup.MarkupTemplateEngine

Other siblings of groovy.text.TemplateEngines have default constructor.