您可以在Grails 3中创建过滤器或拦截器，并检查request.getHeader（User-Agent）移动然后重定向的网址，你想要的。

I have a grails app I am working on at my current job. I have to work on the mobile version of the website and I want to catch in UrlMappings.groovy whether the request is coming from www.mysite.com or m.mysite.com. Any idea how can i do that?

UPDATE:

My current mappings look like this --->

import static org.apache.commons.lang.StringUtils.*

class UrlMappings {
    static mappings = {
        "/$controller/$action?/$id?"{
            constraints {
                // apply constraints here
            }
        }

        "/$lang/$controller/$action?/$id?"{
            language = "${lang}"
            constraints {
                // apply constraints here
            }
        }

        // Start :: Shopping Tools internal URLs
        "/modelLine/build/$year/$modelLineCode/"(controller:'modelLine', action:'build')
        "/colors/index"(controller:'colors', action: 'index')
        "/packages/index"(controller:'packages', action: 'index')
        "/accessories/index"(controller:'accessories', action: 'index')
        "/summary/index"(controller:'summary', action: 'index')

        // Start :: Spanish :: Shopping Tools internal URLs

        "/$lang/modelLine/build/$year/$modelLineCode/"(controller:'modelLine', action:'build')
        "/$lang/colors/index"(controller:'colors', action: 'index')
        "/$lang/packages/index"(controller:'packages', action: 'index')
        "/$lang/accessories/index"(controller:'accessories', action: 'index')
        "/$lang/summary/index"(controller:'summary', action: 'index')

        // End :: Spanish :: Shopping Tools internal URLs
        // End :: Shopping Tools internal URLs


        // Default Home Page
        "/$lang?"(controller:"modelLine", action:"index"){
            constraints {
                lang inList:['en','fr'] // avoids invalid matching
            }
        }

        "/admin"(controller:"admin", action:"index")
        // Error page definitions
        "404"(controller:"errors", action:"notFound")
        "500"(controller:"errors", action:"serverError")
        "403"(view:'/login/denied')
        "402"(view:'/login/denied')
        "401"(view:'/login/denied')
    }
}

How do I change them to detect an m.mysite.com request?

You can create a filter or Interceptor in Grails 3 and check request.getHeader("User-Agent") if it is mobile then redirect the url where ever you want.