Filters

Added by Mike Aizatsky, last edited by Matthew Lachman on Nov 25, 2007  (view change)

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 and plug-ins:
In the case of plug-ins in the order in which the plug-ins load (please clarify previous sentence). 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
   }
}

Each filter you define has a name and a scope. The name is the method name and the scope is defined as named arguments:

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

}

The scope can be one of the following things:

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

Some examples:

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. Takes a first argument as the view model
  • afterView - Executed after view rendering

Some examples

class SecurityFilters {
   def filters = {
       loginCheck(controller:'*', action:'*') {
           before = {
              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

In addition filters support the following methods:

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