Override Grails redirect method - grails

Question

I'm carrying the locale of my Grails application in the URL, such as
http://myapp.com/LANG/controller/action/id.
Therefore, I adjusted the URLMappings.groovy with the language attribute. Since I would like to save work and don't apply the lang parameter at every link, I have overridden the g:link taglib with the language from params.lang. This works pretty good.
When I do a redirect from a controller, such as
redirect(action: "logout")
I'd like to append the params.lang automatically instead of writing every time
redirect(action: "logout", params: [lang: params.lang])
I found the thread grails override redirect controller method, but I'm unsure how to proceed. Where does this code take part?
How can I override the redirect() method and add the params.lang-attribute?
Please advice, thank you very much.

Answer 1

The easiest way to do this in your application would be to use a bit of meta programming and the BootStrap.groovy for your Grails application. The following is just a simple example of what that might look like:
import org.codehaus.groovy.grails.web.servlet.GrailsApplicationAttributes
class BootStrap {
def init = { servletContext ->
def ctx = servletContext.getAttribute(GrailsApplicationAttributes.APPLICATION_CONTEXT)
def app = ctx.getBean("grailsApplication")
app.controllerClasses.each() { controllerClass ->
def oldRedirect = controllerClass.metaClass.pickMethod("redirect", [Map] as Class[])
controllerClass.metaClass.redirect = { Map args ->
// new pre-redirect logic
if (!args['params']) args['params'] = [:] // just in case redirect was called without any parameters
args['params']['whatever'] = 'something' // add something into the parameters map
oldRedirect.invoke delegate, args
// new post-redirect logic
}
}
}
def destroy = {
}
}
The above example just wraps the implementation for redirect on all controllers within your Grails application and injects a new parameter called whatever with the value of something.
The above was tested (quickly) using Grails 2.4.2.