Grails Spring Security Expression - How to access Method parameter - grails

Question

Using the Spring Security Plugin for Grails:
Version: 2.0-RC2
For my controllers I am using the #Secured annotation.
Is there a way to access the method parameter from the spring security expression.#paramName does not work for me.
#Secured(['ROLE_ADMIN',"hasRole('ROLE_USER') && #permissionService.updateAllowed( #myInstance )"])
def update(Bug myInstance) {
The problem: myInstance is null!
Software I am using:
Grails: 2.4.3
Intellij 14
JDK 8

Answer 1

I didn't notice that you were doing this in a controller - there's no support for method args in annotated controllers. The reason for this is that in traditional Spring Security, the annotation is applied to Spring Beans and the bean becomes proxied, and the proxy does the security checks before calling the method and only calls the real method if the checks pass. That works well with Spring MVC controllers because they're regular Java classes, and also in Grails services because there isn't much added to services by Grails - they're really just regular Groovy classes that are auto-registered as Spring Beans, and by default are made transactional.
But controllers are weird. There is actually one SpringMVC controller in any Grails app, and it's internally created and used by Grails. It interacts with the rest of SpringMVC, and delegates to the controller that best matches the url mappings rule for the current request to do its work, and it uses that to create the ModelAndView that Spring expects. Additionally, to support databinding, there's an AST transform that runs on your code during compilation which creates a no-arg method for each method with args, and that is what is called from the Grails internal request handling code. It does databinding and type conversions, and calls the "real" method to handle the request.
The support in Spring Security for working with method args depends on debug information being available in the compiled code, and usually this is not available because it's rarely needed - javac connects everything for us at compile time and getting the value of a method arg from outside of the method isn't often needed. Grails does keep that debug info - that's why this works in a service - but it looks like the AST isn't. It might be possible to get that working, but I have no idea if it is or what would be involved, and to be honest it would likely be a lot of work for a feature that wouldn't be used a lot.
But you can rework the check to pass the params to the service and let it lookup the Bug instance and then do its check. You can access the params from the service, so there's no need to pass anything as args:
import org.springframework.web.context.request.RequestContextHolder
...
def params = RequestContextHolder.requestAttributes.params

Answer 2

I've managed to get a workaround for the problem described in the comments to the accepted answer. Use #this in SpEL expression:
#Secured('#securityService.userCanEditOffer(#this)')
def edit(int id) {..}
Then create such methods in your service:
def userCanEditOffer(WebSecurityExpressionRoot webSecurityExpressionRoot) {
UrlMappingInfo urlMappingInfo = Holders.applicationContext.grailsUrlMappingsHolder.match(webSecurityExpressionRoot.request.forwardURI.substring(webSecurityExpressionRoot.request.contextPath.length()))
userCanEditOffer(Integer.valueOf(urlMappingInfo.params.id))
}
#Transactional(readOnly = true)
def userCanEditOffer(Integer id) { .. }
Inside ulrMappingInfo.params you'll have id, action and controller!