github.com/mreithub/mux
http://www.gorillatoolkit.org/pkg/mux
Package gorilla/mux implements a request router and dispatcher for matching incoming requests to
their respective handler.
The name mux stands for "HTTP request multiplexer". Like the standard http.ServeMux, mux.Router matches incoming requests against a list of registered routes and calls a handler for the route that matches the URL or other conditions. The main features are:
http.Handler interface so it is compatible with the standard http.ServeMux.With a correctly configured Go toolchain:
go get -u github.com/gorilla/mux
Let's start registering a couple of URL paths and handlers:
func main() {
r := mux.NewRouter()
r.HandleFunc("/", HomeHandler)
r.HandleFunc("/products", ProductsHandler)
r.HandleFunc("/articles", ArticlesHandler)
http.Handle("/", r)
}
Here we register three routes mapping URL paths to handlers. This is equivalent to how http.HandleFunc() works: if an incoming request URL matches one of the paths, the corresponding handler is called passing (http.ResponseWriter, *http.Request) as parameters.
Paths can have variables. They are defined using the format {name} or {name:pattern}. If a regular expression pattern is not defined, the matched variable will be anything until the next slash. For example:
r := mux.NewRouter()
r.HandleFunc("/products/{key}", ProductHandler)
r.HandleFunc("/articles/{category}/", ArticlesCategoryHandler)
r.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler)
The names are used to create a map of route variables which can be retrieved calling mux.Vars():
func ArticlesCategoryHandler(w http.ResponseWriter, r *http.Request) {
vars := mux.Vars(r)
w.WriteHeader(http.StatusOK)
fmt.Fprintf(w, "Category: %v\n", vars["category"])
}
And this is all you need to know about the basic usage. More advanced options are explained below.
Routes can also be restricted to a domain or subdomain. Just define a host pattern to be matched. They can also have variables:
r := mux.NewRouter()
// Only matches if domain is "www.example.com".
r.Host("www.example.com")
// Matches a dynamic subdomain.
r.Host("{subdomain:[a-z]+}.domain.com")
There are several other matchers that can be added. To match path prefixes:
r.PathPrefix("/products/")
...or HTTP methods:
r.Methods("GET", "POST")
...or URL schemes:
r.Schemes("https")
...or header values:
r.Headers("X-Requested-With", "XMLHttpRequest")
...or query values:
r.Queries("key", "value")
...or to use a custom matcher function:
r.MatcherFunc(func(r *http.Request, rm *RouteMatch) bool {
return r.ProtoMajor == 0
})
...and finally, it is possible to combine several matchers in a single route:
r.HandleFunc("/products", ProductsHandler).
Host("www.example.com").
Methods("GET").
Schemes("http")
Routes are tested in the order they were added to the router. If two routes match, the first one wins:
r := mux.NewRouter()
r.HandleFunc("/specific", specificHandler)
r.PathPrefix("/").Handler(catchAllHandler)
Setting the same matching conditions again and again can be boring, so we have a way to group several routes that share the same requirements. We call it "subrouting".
For example, let's say we have several URLs that should only match when the host is www.example.com. Create a route for that host and get a "subrouter" from it:
r := mux.NewRouter()
s := r.Host("www.example.com").Subrouter()
Then register routes in the subrouter:
s.HandleFunc("/products/", ProductsHandler)
s.HandleFunc("/products/{key}", ProductHandler)
s.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler)
The three URL paths we registered above will only be tested if the domain is www.example.com, because the subrouter is tested first. This is not only convenient, but also optimizes request matching. You can create subrouters combining any attribute matchers accepted by a route.
Subrouters can be used to create domain or path "namespaces": you define subrouters in a central place and then parts of the app can register its paths relatively to a given subrouter.
There's one more thing about subroutes. When a subrouter has a path prefix, the inner routes use it as base for their paths:
r := mux.NewRouter()
s := r.PathPrefix("/products").Subrouter()
// "/products/"
s.HandleFunc("/", ProductsHandler)
// "/products/{key}/"
s.HandleFunc("/{key}/", ProductHandler)
// "/products/{key}/details"
s.HandleFunc("/{key}/details", ProductDetailsHandler)
Routes on a mux can be listed using the Router.Walk method—useful for generating documentation:
package main
import (
"fmt"
"net/http"
"strings"
"github.com/gorilla/mux"
)
func handler(w http.ResponseWriter, r *http.Request) {
return
}
func main() {
r := mux.NewRouter()
r.HandleFunc("/", handler)
r.HandleFunc("/products", handler).Methods("POST")
r.HandleFunc("/articles", handler).Methods("GET")
r.HandleFunc("/articles/{id}", handler).Methods("GET", "PUT")
r.HandleFunc("/authors", handler).Queries("surname", "{surname}")
r.Walk(func(route *mux.Route, router *mux.Router, ancestors []*mux.Route) error {
t, err := route.GetPathTemplate()
if err != nil {
return err
}
qt, err := route.GetQueriesTemplates()
if err != nil {
return err
}
// p will contain regular expression is compatible with regular expression in Perl, Python, and other languages.
// for instance the regular expression for path '/articles/{id}' will be '^/articles/(?P<v0>[^/]+)$'
p, err := route.GetPathRegexp()
if err != nil {
return err
}
// qr will contain a list of regular expressions with the same semantics as GetPathRegexp,
// just applied to the Queries pairs instead, e.g., 'Queries("surname", "{surname}") will return
// {"^surname=(?P<v0>.*)$}. Where each combined query pair will have an entry in the list.
qr, err := route.GetQueriesRegexp()
if err != nil {
return err
}
m, err := route.GetMethods()
if err != nil {
return err
}
fmt.Println(strings.Join(m, ","), strings.Join(qt, ","), strings.Join(qr, ","), t, p)
return nil
})
http.Handle("/", r)
}
Note that the path provided to PathPrefix() represents a "wildcard": calling
PathPrefix("/static/").Handler(...) means that the handler will be passed any
request that matches "/static/*". This makes it easy to serve static files with mux:
func main() {
var dir string
flag.StringVar(&dir, "dir", ".", "the directory to serve files from. Defaults to the current dir")
flag.Parse()
r := mux.NewRouter()
// This will serve files under http://localhost:8000/static/<filename>
r.PathPrefix("/static/").Handler(http.StripPrefix("/static/", http.FileServer(http.Dir(dir))))
srv := &http.Server{
Handler: r,
Addr: "127.0.0.1:8000",
// Good practice: enforce timeouts for servers you create!
WriteTimeout: 15 * time.Second,
ReadTimeout: 15 * time.Second,
}
log.Fatal(srv.ListenAndServe())
}
Now let's see how to build registered URLs.
Routes can be named. All routes that define a name can have their URLs built, or "reversed". We define a name calling Name() on a route. For example:
r := mux.NewRouter()
r.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler).
Name("article")
To build a URL, get the route and call the URL() method, passing a sequence of key/value pairs for the route variables. For the previous route, we would do:
url, err := r.Get("article").URL("category", "technology", "id", "42")
...and the result will be a url.URL with the following path:
"/articles/technology/42"
This also works for host and query value variables:
r := mux.NewRouter()
r.Host("{subdomain}.domain.com").
Path("/articles/{category}/{id:[0-9]+}").
Queries("filter", "{filter}").
HandlerFunc(ArticleHandler).
Name("article")
// url.String() will be "http://news.domain.com/articles/technology/42?filter=gorilla"
url, err := r.Get("article").URL("subdomain", "news",
"category", "technology",
"id", "42",
"filter", "gorilla")
All variables defined in the route are required, and their values must conform to the corresponding patterns. These requirements guarantee that a generated URL will always match a registered route -- the only exception is for explicitly defined "build-only" routes which never match.
Regex support also exists for matching Headers within a route. For example, we could do:
r.HeadersRegexp("Content-Type", "application/(text|json)")
...and the route will match both requests with a Content-Type of application/json as well as application/text
There's also a way to build only the URL host or path for a route: use the methods URLHost() or URLPath() instead. For the previous route, we would do:
// "http://news.domain.com/"
host, err := r.Get("article").URLHost("subdomain", "news")
// "/articles/technology/42"
path, err := r.Get("article").URLPath("category", "technology", "id", "42")
And if you use subrouters, host and path defined separately can be built as well:
r := mux.NewRouter()
s := r.Host("{subdomain}.domain.com").Subrouter()
s.Path("/articles/{category}/{id:[0-9]+}").
HandlerFunc(ArticleHandler).
Name("article")
// "http://news.domain.com/articles/technology/42"
url, err := r.Get("article").URL("subdomain", "news",
"category", "technology",
"id", "42")
The Walk function on mux.Router can be used to visit all of the routes that are registered on a router. For example,
the following prints all of the registered routes:
r := mux.NewRouter()
r.HandleFunc("/", handler)
r.HandleFunc("/products", handler).Methods("POST")
r.HandleFunc("/articles", handler).Methods("GET")
r.HandleFunc("/articles/{id}", handler).Methods("GET", "PUT")
r.HandleFunc("/authors", handler).Queries("surname", "{surname}")
r.Walk(func(route *mux.Route, router *mux.Router, ancestors []*mux.Route) error {
t, err := route.GetPathTemplate()
if err != nil {
return err
}
qt, err := route.GetQueriesTemplates()
if err != nil {
return err
}
// p will contain a regular expression that is compatible with regular expressions in Perl, Python, and other languages.
// For example, the regular expression for path '/articles/{id}' will be '^/articles/(?P<v0>[^/]+)$'.
p, err := route.GetPathRegexp()
if err != nil {
return err
}
// qr will contain a list of regular expressions with the same semantics as GetPathRegexp,
// just applied to the Queries pairs instead, e.g., 'Queries("surname", "{surname}") will return
// {"^surname=(?P<v0>.*)$}. Where each combined query pair will have an entry in the list.
qr, err := route.GetQueriesRegexp()
if err != nil {
return err
}
m, err := route.GetMethods()
if err != nil {
return err
}
fmt.Println(strings.Join(m, ","), strings.Join(qt, ","), strings.Join(qr, ","), t, p)
return nil
})
Go 1.8 introduced the ability to gracefully shutdown a *http.Server. Here's how to do that alongside mux:
package main
import (
"context"
"flag"
"log"
"net/http"
"os"
"os/signal"
"github.com/gorilla/mux"
)
func main() {
var wait time.Duration
flag.DurationVar(&wait, "graceful-timeout", time.Second * 15, "the duration for which the server gracefully wait for existing connections to finish - e.g. 15s or 1m")
flag.Parse()
r := mux.NewRouter()
// Add your routes as needed
srv := &http.Server{
Addr: "0.0.0.0:8080",
// Good practice to set timeouts to avoid Slowloris attacks.
WriteTimeout: time.Second * 15,
ReadTimeout: time.Second * 15,
IdleTimeout: time.Second * 60,
Handler: r, // Pass our instance of gorilla/mux in.
}
// Run our server in a goroutine so that it doesn't block.
go func() {
if err := srv.ListenAndServe(); err != nil {
log.Println(err)
}
}()
c := make(chan os.Signal, 1)
// We'll accept graceful shutdowns when quit via SIGINT (Ctrl+C)
// SIGKILL, SIGQUIT or SIGTERM (Ctrl+/) will not be caught.
signal.Notify(c, os.Interrupt)
// Block until we receive our signal.
<-c
// Create a deadline to wait for.
ctx, cancel := context.WithTimeout(ctx, wait)
// Doesn't block if no connections, but will otherwise wait
// until the timeout deadline.
srv.Shutdown(ctx)
// Optionally, you could run srv.Shutdown in a goroutine and block on
// <-ctx.Done() if your application should wait for other services
// to finalize based on context cancellation.
log.Println("shutting down")
os.Exit(0)
}
Mux supports the addition of middlewares to a Router, which are executed in the order they are added if a match is found, including its subrouters.
Middlewares are (typically) small pieces of code which take one request, do something with it, and pass it down to another middleware or the final handler. Some common use cases for middleware are request logging, header manipulation, or ResponseWriter hijacking.
Mux middlewares are defined using the de facto standard type:
type MiddlewareFunc func(http.Handler) http.Handler
Typically, the returned handler is a closure which does something with the http.ResponseWriter and http.Request passed to it, and then calls the handler passed as parameter to the MiddlewareFunc. This takes advantage of closures being able access variables from the context where they are created, while retaining the signature enforced by the receivers.
A very basic middleware which logs the URI of the request being handled could be written as:
func simpleMw(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// Do stuff here
log.Println(r.RequestURI)
// Call the next handler, which can be another middleware in the chain, or the final handler.
next.ServeHTTP(w, r)
})
}
Middlewares can be added to a router using Router.AddMiddlewareFunc():
r := mux.NewRouter()
r.HandleFunc("/", handler)
r.AddMiddleware(simpleMw)
A more complex authentication middleware, which maps session token to users, could be written as:
// Define our struct
type authenticationMiddleware struct {
tokenUsers map[string]string
}
// Initialize it somewhere
func (amw *authenticationMiddleware) Populate() {
amw.tokenUsers["00000000"] = "user0"
amw.tokenUsers["aaaaaaaa"] = "userA"
amw.tokenUsers["05f717e5"] = "randomUser"
amw.tokenUsers["deadbeef"] = "user0"
}
// Middleware function, which will be called for each request
func (amw *authenticationMiddleware) Middleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
token := r.Header.Get("X-Session-Token")
if user, found := amw.tokenUsers[token]; found {
// We found the token in our map
log.Printf("Authenticated user %s\n", user)
// Pass down the request to the next middleware (or final handler)
next.ServeHTTP(w, r)
} else {
// Write an error and stop the handler chain
http.Error(w, "Forbidden", 403)
}
})
}
r := mux.NewRouter()
r.HandleFunc("/", handler)
amw := authenticationMiddleware{}
amw.Populate()
r.AddMiddlewareFunc(amw.Middleware)
Note: The handler chain will be stopped if your middleware doesn't call next.ServeHTTP() with the corresponding parameters. This can be used to abort a request if the middleware writer wants to. Middlewares should write to ResponseWriter if they are going to terminate the request, and they should not write to ResponseWriter if they are not going to terminate it.
Here's a complete, runnable example of a small mux based server:
package main
import (
"net/http"
"log"
"github.com/gorilla/mux"
)
func YourHandler(w http.ResponseWriter, r *http.Request) {
w.Write([]byte("Gorilla!\n"))
}
func main() {
r := mux.NewRouter()
// Routes consist of a path and a handler function.
r.HandleFunc("/", YourHandler)
// Bind to a port and pass our router in
log.Fatal(http.ListenAndServe(":8000", r))
}
BSD licensed. See the LICENSE file for details.
FAQs
Unknown package
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
Research
Security News
Socket’s threat research team has detected six malicious npm packages typosquatting popular libraries to insert SSH backdoors.
Security News
MITRE's 2024 CWE Top 25 highlights critical software vulnerabilities like XSS, SQL Injection, and CSRF, reflecting shifts due to a refined ranking methodology.
Security News
In this segment of the Risky Business podcast, Feross Aboukhadijeh and Patrick Gray discuss the challenges of tracking malware discovered in open source softare.