Starting with 1.4.0 release, it is possible to use Groovy DSL to build the WroModel. In order to use it, just create the wro.groovy file instead of wro.xml and place it to the same location (in WEB-INF folder).


Here is an example of how wroModel built with Groovy:

groups {
  group1 {
  group2 {
    css(minimize: false, "/css/*.css")
    css "/css/*.less"
    js "/js/*.js"
    js "/js/"
  "just-another-group" {
  all {

As you can see in this example, groovy DSL is very flexible and allows you specify groups & resources in multiple ways. It is less verbose than XML and can be easily used as the first choice.

The class handling the creation of wroModel using Groovy DSL is called !GroovyModelFactory. This class is located in wro4j-extensions project, because it requires groovy dependency.

Using Groovy DSL

If you like the groovy DSL, in order to switch from the xml, all you have to do is to create wro.groovy and remove old wro.xml. This will work out of the box, because the default model used by !WroManagerFactory is called SmartWroModelFactory which will use all existing model factories in order to build the model. It will try to build model in that order: xml, groovy, json. If none of these DSL is found, it will throw an exception.

Another explicit way of using groovy DSL is to override the newModelFactory method from BaseWroManagerFactory class:

public CustomWroManagerFactory extends BaseWroManagerFactory() {
  protected WroModelFactory newModelFactory(final ServletContext servletContext) {
    return new GroovyModelFactory() {
      protected InputStream getModelResourceAsStream() throws IOException {
        return //the stream of the groovy object describing the model.

The above code creates an extension of !BaseWroManagerFactory and inform the WroManager to use a new factory for creating WroModel object based on Groovy.