beforeInterceptor
Purpose
Allows the interception of an action before it is executed. A beforeInterceptor can optionally halt execution of the action.
Examples
Simple tracing interceptor:
def beforeInterceptor = {
println "Tracing action ${actionUri}"
}A trivial security interceptor to implement login functionality:
def beforeInterceptor = [action: this.&auth, except: 'login']// defined with private scope, so it's not considered an action private auth() { if (!session.user) { redirect(action: 'login') return false } }
def login() { // display login page }
Description
The beforeInterceptor intercepts processing before the action is executed. If it returns false then the action will not be executed. The interceptor can be defined for all actions in a controller as follows:
def beforeInterceptor = {
println "Tracing action ${actionUri}"
}This declaration must be a class-scope Closure in the controller class. It will execute before all actions and does not interfere with processing since it returns no value. A common use case however is for simple authentication (although a security plugin is preferred):
def beforeInterceptor = [action: this.&auth, except: 'login']// defined with private scope, so it's not considered an action private auth() { if (!session.user) { redirect(action: 'login') return false } }
def login() { // display login page }
This defines a method called auth. It is declared as a private method so it is not exposed as a controller action. The beforeInterceptor then defines an interceptor that is used on all actions except the login action and is configured using Groovy's method pointer syntax to execute the auth method. The auth method will redirect to another page if it doesn't find a user in the session, and it signifies that it has handled the response and that the requested action should not be processed by returning false.
This example limited the intercepted actions using the except argument but the only argument can also be used to list the actions to be intercepted, rather than those to not intercept.