When registering handlers in Go (language) is there any way to specify wildcards in the pattern?
For example:
http.HandleFunc("/groups/*/people", peopleInGroupHandler)
Where the * could be any valid URL string. Or is the only solution to match /groups and figure the rest out from within the handler (peopleInGroupHandler) func?
The patterns for http.Handler and http.HandleFunc aren't regular expressions or globs. There isn't a way to specify wildcards. They're documented here.
That said, it's not too hard to create your own handler that can use regular expressions or any other kind of pattern you want. Here's one that uses regular expressions (compiled, but not tested):
type route struct {
pattern *regexp.Regexp
handler http.Handler
}
type RegexpHandler struct {
routes []*route
}
func (h *RegexpHandler) Handler(pattern *regexp.Regexp, handler http.Handler) {
h.routes = append(h.routes, &route{pattern, handler})
}
func (h *RegexpHandler) HandleFunc(pattern *regexp.Regexp, handler func(http.ResponseWriter, *http.Request)) {
h.routes = append(h.routes, &route{pattern, http.HandlerFunc(handler)})
}
func (h *RegexpHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
for _, route := range h.routes {
if route.pattern.MatchString(r.URL.Path) {
route.handler.ServeHTTP(w, r)
return
}
}
// no pattern matched; send 404 response
http.NotFound(w, r)
}
Beego, the answer to all the Golang web server questions. Wetalk is a blog site built on Beego.
Since 2011, you can now (2014+) find other solutions.
For instance, the mux package of the Gorilla Web toolkit provides all kind of routing options:
It can be easily integrated to any BYOR (Bring your own Router) http library, like negroni.
Here is an example from the article "Gorilla vs Pat vs Routes: A Mux Showdown":
package main
import (
"github.com/gorilla/mux"
"log"
"net/http"
)
func main() {
rtr := mux.NewRouter()
rtr.HandleFunc("/user/{name:[a-z]+}/profile", profile).Methods("GET")
http.Handle("/", rtr)
log.Println("Listening...")
http.ListenAndServe(":3000", nil)
}
func profile(w http.ResponseWriter, r *http.Request) {
params := mux.Vars(r)
name := params["name"]
w.Write([]byte("Hello " + name))
}
Sometimes better not to just use yet another "magic" package, but understand what's going on under the hood
In this instance, the "magic" is defined in "gorilla/mux/regexp.go", and tested here.
The idea is to extract named variables, assemble a regexp to be matched, create a "reverse" template to build URLs and compile regexps to validate variable values used in URL building.
I just wanted to add julienschmidt/httprouter, which just behaves like net/http but with an additional parameter for url-values and support for request methods:
https://github.com/julienschmidt/httprouter
package main
import (
"fmt"
"github.com/julienschmidt/httprouter"
"net/http"
"log"
)
func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
fmt.Fprint(w, "Welcome!
")
}
func Hello(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
fmt.Fprintf(w, "hello, %s!
", ps.ByName("name"))
}
func main() {
router := httprouter.New()
router.GET("/", Index)
router.GET("/hello/:name", Hello)
log.Fatal(http.ListenAndServe(":8080", router))
}
It also seems to be slightly more popular than gorilla/mux (according to GitHub) and it also claims to need less memory.
You could check how violetear handles dynamic + catchall (wildcard) patterns, this is just for complement for example:
uuid := `[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}`
router.AddRegex(":uuid")
router.HandleFunc("/test/:uuid/:uuid", handleUUID, "GET,HEAD")
In this case, the request may have 2 different UUIDS
For a dynamic/wildcard this could apply:
http://api.violetear.org/command/ping/127.0.0.1
\______/\___/\________/
| | |
static |
dynamic
A regex may be used to match the IP:
router.AddRegex(":ip", `^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$`)
router.HandleFunc("/command/ping/:ip", ipHandler, "GET")
Or simply just a catch all allowing GET and HEAD methods only:
router.HandleFunc("/command/ping/*", anyHandler, "GET, HEAD")
More examples can be found here: https://violetear.org/post/how-it-works/
Here's an example of how to use the code example from @evanshaw
func handleDigits(res http.ResponseWriter, req *http.Request) {
res.Write([]byte("Digits in the URL
"))
}
func handleStrings(res http.ResponseWriter, req *http.Request) {
res.Write([]byte("Strings in the URL
"))
}
func main() {
handler := &RegexpHandler{}
reg1, _ := regexp.Compile("/foo-\\d+")
handler.HandleFunc(reg1, handleDigits)
reg2, _ := regexp.Compile("/foo-\\w+")
handler.HandleFunc(reg2, handleStrings)
http.ListenAndServe(":3000", handler)
}