Grails Filters

Since Grails 1.0, Grails supports the concept of filters that can be applied independently of controllers by users or plug-ins. The filters are executed in the order they are defined.

Note on filters from plugins: Filters from plugins are loaded in the order in which the plugins are loaded. It is therefore important that if you want a filter to be executed after another known filter within another plug-in, you must "depend on" that plug-in using the dependsOn attribute. See Plugin Dependencies.

Defining Filters

To create a filter create a class that ends with "Filters" in the grails-app/conf directory. Within this class define a code block called filters that contains the filter definitions:

class MyFilters {
   def filters = {
        // your filters here
   }
}

myFilter(controller:'*', action:'*') {
}

• A controller and/or action name pairing with optional wildcards
• A URI

all(controller:'*', action:'*') {
}
justBook(controller:'book', action:'*') {
}
someURIs(uri:'/book/*') {
}
allURIs(uri:'/**') {
}

Filter Interceptors

Within the body of the filter you can then define one of the following interceptors for the filter:

• before - Executed before the action. Can return false to indicate all future filters and the action should not execute.
• after - Executed after an action. Called with the view model as first argument
• afterView - Executed after view rendering

class SecurityFilters {
   def filters = {
       loginCheck(controller:'*', action:'*') {
           before = {
              if (params.controller == null) { 
                 redirect(action:'login')
                 /* When using Tomcat and the controller is null you must 
                    return true. Otherwise an exception is thrown. */
                 return true
              }
              else if(!session.user && !actionName.equals('login')) {
                  redirect(action:'login')
                  return false
               }
           }
       }
   }
}

Filter Dynamic Methods/Properties

Filters support most of the common properties available to controllers and tag libraries including:

• request - The HttpServletRequest object
• response - The HttpServletResponse object
• session - The HttpSession object
• servletContext - The ServletContext object
• applicationContext - The ApplicationContext object
• params - The request parameters object
• actionName - The action name that is being dispatched to
• controllerName - The controller name that is being dispatched to

• redirect
• render