README
¶
gorilla/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:
- It implements the
http.Handlerinterface so it is compatible with the standardhttp.ServeMux. - Requests can be matched based on URL host, path, path prefix, schemes, header and query values, HTTP methods or using custom matchers.
- URL hosts, paths and query values can have variables with an optional regular expression.
- Registered URLs can be built, or "reversed", which helps maintaining references to resources.
- Routes can be used as subrouters: nested routes are only tested if the parent route matches. This is useful to define groups of routes that share common conditions like a host, a path prefix or other repeated attributes. As a bonus, this optimizes request matching.
- Install
- Examples
- Matching Routes
- Static Files
- Registered URLs
- Walking Routes
- Graceful Shutdown
- Middleware
- Testing Handlers
- Full Example
Install
With a correctly configured Go toolchain:
go get -u github.com/gorilla/mux
Examples
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.
Matching Routes
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)
Static Files
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())
}
Registered URLs
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")
Walking Routes
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:
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}")
err := r.Walk(func(route *mux.Route, router *mux.Router, ancestors []*mux.Route) error {
pathTemplate, err := route.GetPathTemplate()
if err == nil {
fmt.Println("ROUTE:", pathTemplate)
}
pathRegexp, err := route.GetPathRegexp()
if err == nil {
fmt.Println("Path regexp:", pathRegexp)
}
queriesTemplates, err := route.GetQueriesTemplates()
if err == nil {
fmt.Println("Queries templates:", strings.Join(queriesTemplates, ","))
}
queriesRegexps, err := route.GetQueriesRegexp()
if err == nil {
fmt.Println("Queries regexps:", strings.Join(queriesRegexps, ","))
}
methods, err := route.GetMethods()
if err == nil {
fmt.Println("Methods:", strings.Join(methods, ","))
}
fmt.Println()
return nil
})
if err != nil {
fmt.Println(err)
}
http.Handle("/", r)
}
Graceful Shutdown
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"
"time"
"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(context.Background(), wait)
defer cancel()
// 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)
}
Middleware
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 loggingMiddleware(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.Use():
r := mux.NewRouter()
r.HandleFunc("/", handler)
r.Use(loggingMiddleware)
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", http.StatusForbidden)
}
})
}
r := mux.NewRouter()
r.HandleFunc("/", handler)
amw := authenticationMiddleware{}
amw.Populate()
r.Use(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.
Testing Handlers
Testing handlers in a Go web application is straightforward, and mux doesn't complicate this any further. Given two files: endpoints.go and endpoints_test.go, here's how we'd test an application using mux.
First, our simple HTTP handler:
// endpoints.go
package main
func HealthCheckHandler(w http.ResponseWriter, r *http.Request) {
// A very simple health check.
w.WriteHeader(http.StatusOK)
w.Header().Set("Content-Type", "application/json")
// In the future we could report back on the status of our DB, or our cache
// (e.g. Redis) by performing a simple PING, and include them in the response.
io.WriteString(w, `{"alive": true}`)
}
func main() {
r := mux.NewRouter()
r.HandleFunc("/health", HealthCheckHandler)
log.Fatal(http.ListenAndServe("localhost:8080", r))
}
Our test code:
// endpoints_test.go
package main
import (
"net/http"
"net/http/httptest"
"testing"
)
func TestHealthCheckHandler(t *testing.T) {
// Create a request to pass to our handler. We don't have any query parameters for now, so we'll
// pass 'nil' as the third parameter.
req, err := http.NewRequest("GET", "/health", nil)
if err != nil {
t.Fatal(err)
}
// We create a ResponseRecorder (which satisfies http.ResponseWriter) to record the response.
rr := httptest.NewRecorder()
handler := http.HandlerFunc(HealthCheckHandler)
// Our handlers satisfy http.Handler, so we can call their ServeHTTP method
// directly and pass in our Request and ResponseRecorder.
handler.ServeHTTP(rr, req)
// Check the status code is what we expect.
if status := rr.Code; status != http.StatusOK {
t.Errorf("handler returned wrong status code: got %v want %v",
status, http.StatusOK)
}
// Check the response body is what we expect.
expected := `{"alive": true}`
if rr.Body.String() != expected {
t.Errorf("handler returned unexpected body: got %v want %v",
rr.Body.String(), expected)
}
}
In the case that our routes have variables, we can pass those in the request. We could write table-driven tests to test multiple possible route variables as needed.
// endpoints.go
func main() {
r := mux.NewRouter()
// A route with a route variable:
r.HandleFunc("/metrics/{type}", MetricsHandler)
log.Fatal(http.ListenAndServe("localhost:8080", r))
}
Our test file, with a table-driven test of routeVariables:
// endpoints_test.go
func TestMetricsHandler(t *testing.T) {
tt := []struct{
routeVariable string
shouldPass bool
}{
{"goroutines", true},
{"heap", true},
{"counters", true},
{"queries", true},
{"adhadaeqm3k", false},
}
for _, tc := range tt {
path := fmt.Sprintf("/metrics/%s", tc.routeVariable)
req, err := http.NewRequest("GET", path, nil)
if err != nil {
t.Fatal(err)
}
rr := httptest.NewRecorder()
// Need to create a router that we can pass the request through so that the vars will be added to the context
router := mux.NewRouter()
router.HandleFunc("/metrics/{type}", MetricsHandler)
router.ServeHTTP(rr, req)
// In this case, our MetricsHandler returns a non-200 response
// for a route variable it doesn't know about.
if rr.Code == http.StatusOK && !tc.shouldPass {
t.Errorf("handler should have failed on routeVariable %s: got %v want %v",
tc.routeVariable, rr.Code, http.StatusOK)
}
}
}
Full Example
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))
}
License
BSD licensed. See the LICENSE file for details.
Documentation
¶
Overview ¶
Package mux implements a request router and dispatcher.
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:
- Requests can be matched based on URL host, path, path prefix, schemes, header and query values, HTTP methods or using custom matchers.
- URL hosts, paths and query values can have variables with an optional regular expression.
- Registered URLs can be built, or "reversed", which helps maintaining references to resources.
- Routes can be used as subrouters: nested routes are only tested if the parent route matches. This is useful to define groups of routes that share common conditions like a host, a path prefix or other repeated attributes. As a bonus, this optimizes request matching.
- It implements the http.Handler interface so it is compatible with the standard http.ServeMux.
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)
Groups can be used inside patterns, as long as they are non-capturing (?:re). For example:
r.HandleFunc("/articles/{category}/{sort:(?:asc|desc|new)}", ArticlesCategoryHandler)
The names are used to create a map of route variables which can be retrieved calling mux.Vars():
vars := mux.Vars(request) category := vars["category"]
Note that if any capturing groups are present, mux will panic() during parsing. To prevent this, convert any capturing groups to non-capturing, e.g. change "/{sort:(asc|desc)}" to "/{sort:(?:asc|desc)}". This is a change from prior versions which behaved unpredictably when capturing groups were present.
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")
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)
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")
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.
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 (closures can access variables from the context where they are created).
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.Use()`:
r := mux.NewRouter()
r.HandleFunc("/", handler)
r.Use(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)
next.ServeHTTP(w, r)
} else {
http.Error(w, "Forbidden", http.StatusForbidden)
}
})
}
r := mux.NewRouter()
r.HandleFunc("/", handler)
amw := authenticationMiddleware{}
amw.Populate()
r.Use(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.
Example (AuthenticationMiddleware) ¶
package main
import (
"log"
"net/http"
"github.com/gorilla/mux"
)
// 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)
next.ServeHTTP(w, r)
} else {
http.Error(w, "Forbidden", http.StatusForbidden)
}
})
}
func main() {
r := mux.NewRouter()
r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
// Do something here
})
amw := authenticationMiddleware{}
amw.Populate()
r.Use(amw.Middleware)
}
Output:
Index ¶
- Variables
- func SetURLVars(r *http.Request, val map[string]string) *http.Request
- func Vars(r *http.Request) map[string]string
- type BuildVarsFunc
- type MatcherFunc
- type MiddlewareFunc
- type Route
- func (r *Route) BuildOnly() *Route
- func (r *Route) BuildVarsFunc(f BuildVarsFunc) *Route
- func (r *Route) GetError() error
- func (r *Route) GetHandler() http.Handler
- func (r *Route) GetHostTemplate() (string, error)
- func (r *Route) GetMethods() ([]string, error)
- func (r *Route) GetName() string
- func (r *Route) GetPathRegexp() (string, error)
- func (r *Route) GetPathTemplate() (string, error)
- func (r *Route) GetQueriesRegexp() ([]string, error)
- func (r *Route) GetQueriesTemplates() ([]string, error)
- func (r *Route) Handler(handler http.Handler) *Route
- func (r *Route) HandlerFunc(f func(http.ResponseWriter, *http.Request)) *Route
- func (r *Route) Headers(pairs ...string) *Route
- func (r *Route) HeadersRegexp(pairs ...string) *Route
- func (r *Route) Host(tpl string) *Route
- func (r *Route) Match(req *http.Request, match *RouteMatch) bool
- func (r *Route) MatcherFunc(f MatcherFunc) *Route
- func (r *Route) Methods(methods ...string) *Route
- func (r *Route) Name(name string) *Route
- func (r *Route) Path(tpl string) *Route
- func (r *Route) PathPrefix(tpl string) *Route
- func (r *Route) Queries(pairs ...string) *Route
- func (r *Route) Schemes(schemes ...string) *Route
- func (r *Route) SkipClean() bool
- func (r *Route) Subrouter() *Router
- func (r *Route) URL(pairs ...string) (*url.URL, error)
- func (r *Route) URLHost(pairs ...string) (*url.URL, error)
- func (r *Route) URLPath(pairs ...string) (*url.URL, error)
- type RouteMatch
- type Router
- func (r *Router) BuildVarsFunc(f BuildVarsFunc) *Route
- func (r *Router) Get(name string) *Route
- func (r *Router) GetRoute(name string) *Route
- func (r *Router) Handle(path string, handler http.Handler) *Route
- func (r *Router) HandleFunc(path string, f func(http.ResponseWriter, *http.Request)) *Route
- func (r *Router) Headers(pairs ...string) *Route
- func (r *Router) Host(tpl string) *Route
- func (r *Router) Match(req *http.Request, match *RouteMatch) bool
- func (r *Router) MatcherFunc(f MatcherFunc) *Route
- func (r *Router) Methods(methods ...string) *Route
- func (r *Router) NewRoute() *Route
- func (r *Router) Path(tpl string) *Route
- func (r *Router) PathPrefix(tpl string) *Route
- func (r *Router) Queries(pairs ...string) *Route
- func (r *Router) Schemes(schemes ...string) *Route
- func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request)
- func (r *Router) SkipClean(value bool) *Router
- func (r *Router) StrictSlash(value bool) *Router
- func (r *Router) Use(mwf ...MiddlewareFunc)
- func (r *Router) UseEncodedPath() *Router
- func (r *Router) Walk(walkFn WalkFunc) error
- type WalkFunc
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var ( // ErrMethodMismatch is returned when the method in the request does not match // the method defined against the route. ErrMethodMismatch = errors.New("method is not allowed") // ErrNotFound is returned when no route match is found. ErrNotFound = errors.New("no matching route was found") )
var SkipRouter = errors.New("skip this router")
SkipRouter is used as a return value from WalkFuncs to indicate that the router that walk is about to descend down to should be skipped.
Functions ¶
func SetURLVars ¶ added in v1.6.1
SetURLVars sets the URL variables for the given request, to be accessed via mux.Vars for testing route behaviour. Arguments are not modified, a shallow copy is returned.
This API should only be used for testing purposes; it provides a way to inject variables into the request context. Alternatively, URL variables can be set by making a route that captures the required variables, starting a server and sending the request to that server.
Example ¶
req, _ := http.NewRequest("GET", "/foo", nil)
req = SetURLVars(req, map[string]string{"foo": "bar"})
fmt.Println(Vars(req)["foo"])
Output: bar
Types ¶
type BuildVarsFunc ¶
BuildVarsFunc is the function signature used by custom build variable functions (which can modify route variables before a route's URL is built).
type MatcherFunc ¶
type MatcherFunc func(*http.Request, *RouteMatch) bool
MatcherFunc is the function signature used by custom matchers.
func (MatcherFunc) Match ¶
func (m MatcherFunc) Match(r *http.Request, match *RouteMatch) bool
Match returns the match for a given request.
type MiddlewareFunc ¶ added in v1.6.1
MiddlewareFunc is a function which receives an http.Handler and returns another 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.
func CORSMethodMiddleware ¶ added in v1.6.2
func CORSMethodMiddleware(r *Router) MiddlewareFunc
CORSMethodMiddleware sets the Access-Control-Allow-Methods response header on a request, by matching routes based only on paths. It also handles OPTIONS requests, by settings Access-Control-Allow-Methods, and then returning without calling the next http handler.
func (MiddlewareFunc) Middleware ¶ added in v1.6.1
func (mw MiddlewareFunc) Middleware(handler http.Handler) http.Handler
Middleware allows MiddlewareFunc to implement the middleware interface.
type Route ¶
type Route struct {
// contains filtered or unexported fields
}
Route stores information to match a request and build URLs.
func CurrentRoute ¶
CurrentRoute returns the matched route for the current request, if any. This only works when called inside the handler of the matched route because the matched route is stored in the request context which is cleared after the handler returns, unless the KeepContext option is set on the Router.
func (*Route) BuildVarsFunc ¶
func (r *Route) BuildVarsFunc(f BuildVarsFunc) *Route
BuildVarsFunc adds a custom function to be used to modify build variables before a route's URL is built.
func (*Route) GetHandler ¶
GetHandler returns the handler for the route, if any.
func (*Route) GetHostTemplate ¶
GetHostTemplate returns the template used to build the route match. This is useful for building simple REST API documentation and for instrumentation against third-party services. An error will be returned if the route does not define a host.
func (*Route) GetMethods ¶ added in v1.4.0
GetMethods returns the methods the route matches against This is useful for building simple REST API documentation and for instrumentation against third-party services. An error will be returned if route does not have methods.
func (*Route) GetPathRegexp ¶ added in v1.4.0
GetPathRegexp returns the expanded regular expression used to match route path. This is useful for building simple REST API documentation and for instrumentation against third-party services. An error will be returned if the route does not define a path.
func (*Route) GetPathTemplate ¶
GetPathTemplate returns the template used to build the route match. This is useful for building simple REST API documentation and for instrumentation against third-party services. An error will be returned if the route does not define a path.
func (*Route) GetQueriesRegexp ¶ added in v1.6.0
GetQueriesRegexp returns the expanded regular expressions used to match the route queries. This is useful for building simple REST API documentation and for instrumentation against third-party services. An error will be returned if the route does not have queries.
func (*Route) GetQueriesTemplates ¶ added in v1.6.0
GetQueriesTemplates returns the templates used to build the query matching. This is useful for building simple REST API documentation and for instrumentation against third-party services. An error will be returned if the route does not define queries.
func (*Route) HandlerFunc ¶
HandlerFunc sets a handler function for the route.
func (*Route) Headers ¶
Headers adds a matcher for request header values. It accepts a sequence of key/value pairs to be matched. For example:
r := mux.NewRouter()
r.Headers("Content-Type", "application/json",
"X-Requested-With", "XMLHttpRequest")
The above route will only match if both request header values match. If the value is an empty string, it will match any value if the key is set.
func (*Route) HeadersRegexp ¶
HeadersRegexp accepts a sequence of key/value pairs, where the value has regex support. For example:
r := mux.NewRouter()
r.HeadersRegexp("Content-Type", "application/(text|json)",
"X-Requested-With", "XMLHttpRequest")
The above route will only match if both the request header matches both regular expressions. If the value is an empty string, it will match any value if the key is set. Use the start and end of string anchors (^ and $) to match an exact value.
Example ¶
This example demonstrates setting a regular expression matcher for the header value. A plain word will match any value that contains a matching substring as if the pattern was wrapped with `.*`.
package main
import (
"fmt"
"net/http"
"github.com/gorilla/mux"
)
func main() {
r := mux.NewRouter()
route := r.NewRoute().HeadersRegexp("Accept", "html")
req1, _ := http.NewRequest("GET", "example.com", nil)
req1.Header.Add("Accept", "text/plain")
req1.Header.Add("Accept", "text/html")
req2, _ := http.NewRequest("GET", "example.com", nil)
req2.Header.Set("Accept", "application/xhtml+xml")
matchInfo := &mux.RouteMatch{}
fmt.Printf("Match: %v %q\n", route.Match(req1, matchInfo), req1.Header["Accept"])
fmt.Printf("Match: %v %q\n", route.Match(req2, matchInfo), req2.Header["Accept"])
}
Output: Match: true ["text/plain" "text/html"] Match: true ["application/xhtml+xml"]
Example (ExactMatch) ¶
This example demonstrates setting a strict regular expression matcher for the header value. Using the start and end of string anchors, the value must be an exact match.
package main
import (
"fmt"
"net/http"
"github.com/gorilla/mux"
)
func main() {
r := mux.NewRouter()
route := r.NewRoute().HeadersRegexp("Origin", "^https://example.co$")
yes, _ := http.NewRequest("GET", "example.co", nil)
yes.Header.Set("Origin", "https://example.co")
no, _ := http.NewRequest("GET", "example.co.uk", nil)
no.Header.Set("Origin", "https://example.co.uk")
matchInfo := &mux.RouteMatch{}
fmt.Printf("Match: %v %q\n", route.Match(yes, matchInfo), yes.Header["Origin"])
fmt.Printf("Match: %v %q\n", route.Match(no, matchInfo), no.Header["Origin"])
}
Output: Match: true ["https://example.co"] Match: false ["https://example.co.uk"]
func (*Route) Host ¶
Host adds a matcher for the URL host. It accepts a template with zero or more URL variables enclosed by {}. Variables can define an optional regexp pattern to be matched:
- {name} matches anything until the next dot.
- {name:pattern} matches the given regexp pattern.
For example:
r := mux.NewRouter()
r.Host("www.example.com")
r.Host("{subdomain}.domain.com")
r.Host("{subdomain:[a-z]+}.domain.com")
Variable names must be unique in a given route. They can be retrieved calling mux.Vars(request).
func (*Route) Match ¶
func (r *Route) Match(req *http.Request, match *RouteMatch) bool
Match matches the route against the request.
func (*Route) MatcherFunc ¶
func (r *Route) MatcherFunc(f MatcherFunc) *Route
MatcherFunc adds a custom function to be used as request matcher.
func (*Route) Methods ¶
Methods adds a matcher for HTTP methods. It accepts a sequence of one or more methods to be matched, e.g.: "GET", "POST", "PUT".
func (*Route) Name ¶
Name sets the name for the route, used to build URLs. If the name was registered already it will be overwritten.
func (*Route) Path ¶
Path adds a matcher for the URL path. It accepts a template with zero or more URL variables enclosed by {}. The template must start with a "/". Variables can define an optional regexp pattern to be matched:
- {name} matches anything until the next slash.
- {name:pattern} matches the given regexp pattern.
For example:
r := mux.NewRouter()
r.Path("/products/").Handler(ProductsHandler)
r.Path("/products/{key}").Handler(ProductsHandler)
r.Path("/articles/{category}/{id:[0-9]+}").
Handler(ArticleHandler)
Variable names must be unique in a given route. They can be retrieved calling mux.Vars(request).
func (*Route) PathPrefix ¶
PathPrefix adds a matcher for the URL path prefix. This matches if the given template is a prefix of the full URL path. See Route.Path() for details on the tpl argument.
Note that it does not treat slashes specially ("/foobar/" will be matched by the prefix "/foo") so you may want to use a trailing slash here.
Also note that the setting of Router.StrictSlash() has no effect on routes with a PathPrefix matcher.
func (*Route) Queries ¶
Queries adds a matcher for URL query values. It accepts a sequence of key/value pairs. Values may define variables. For example:
r := mux.NewRouter()
r.Queries("foo", "bar", "id", "{id:[0-9]+}")
The above route will only match if the URL contains the defined queries values, e.g.: ?foo=bar&id=42.
It the value is an empty string, it will match any value if the key is set.
Variables can define an optional regexp pattern to be matched:
- {name} matches anything until the next slash.
- {name:pattern} matches the given regexp pattern.
func (*Route) Schemes ¶
Schemes adds a matcher for URL schemes. It accepts a sequence of schemes to be matched, e.g.: "http", "https".
func (*Route) SkipClean ¶
SkipClean reports whether path cleaning is enabled for this route via Router.SkipClean.
func (*Route) Subrouter ¶
Subrouter creates a subrouter for the route.
It will test the inner routes only if the parent route matched. For example:
r := mux.NewRouter()
s := r.Host("www.example.com").Subrouter()
s.HandleFunc("/products/", ProductsHandler)
s.HandleFunc("/products/{key}", ProductHandler)
s.HandleFunc("/articles/{category}/{id:[0-9]+}"), ArticleHandler)
Here, the routes registered in the subrouter won't be tested if the host doesn't match.
func (*Route) URL ¶
URL builds a URL for the route.
It accepts a sequence of key/value pairs for the route variables. For example, given this route:
r := mux.NewRouter()
r.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler).
Name("article")
...a URL for it can be built using:
url, err := r.Get("article").URL("category", "technology", "id", "42")
...which will return an url.URL with the following path:
"/articles/technology/42"
This also works for host variables:
r := mux.NewRouter()
r.Host("{subdomain}.domain.com").
HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler).
Name("article")
// url.String() will be "http://news.domain.com/articles/technology/42"
url, err := r.Get("article").URL("subdomain", "news",
"category", "technology",
"id", "42")
All variables defined in the route are required, and their values must conform to the corresponding patterns.
type RouteMatch ¶
type RouteMatch struct {
Route *Route
Handler http.Handler
Vars map[string]string
// MatchErr is set to appropriate matching error
// It is set to ErrMethodMismatch if there is a mismatch in
// the request method and route method
MatchErr error
}
RouteMatch stores information about a matched route.
type Router ¶
type Router struct {
// Configurable Handler to be used when no route matches.
NotFoundHandler http.Handler
// Configurable Handler to be used when the request method does not match the route.
MethodNotAllowedHandler http.Handler
// If true, do not clear the request context after handling the request.
// This has no effect when go1.7+ is used, since the context is stored
// on the request itself.
KeepContext bool
// contains filtered or unexported fields
}
Router registers routes to be matched and dispatches a handler.
It implements the http.Handler interface, so it can be registered to serve requests:
var router = mux.NewRouter()
func main() {
http.Handle("/", router)
}
Or, for Google App Engine, register it in a init() function:
func init() {
http.Handle("/", router)
}
This will send all incoming requests to the router.
func (*Router) BuildVarsFunc ¶
func (r *Router) BuildVarsFunc(f BuildVarsFunc) *Route
BuildVarsFunc registers a new route with a custom function for modifying route variables before building a URL.
func (*Router) GetRoute ¶
GetRoute returns a route registered with the given name. This method was renamed to Get() and remains here for backwards compatibility.
func (*Router) Handle ¶
Handle registers a new route with a matcher for the URL path. See Route.Path() and Route.Handler().
func (*Router) HandleFunc ¶
HandleFunc registers a new route with a matcher for the URL path. See Route.Path() and Route.HandlerFunc().
func (*Router) Headers ¶
Headers registers a new route with a matcher for request header values. See Route.Headers().
func (*Router) Match ¶
func (r *Router) Match(req *http.Request, match *RouteMatch) bool
Match attempts to match the given request against the router's registered routes.
If the request matches a route of this router or one of its subrouters the Route, Handler, and Vars fields of the the match argument are filled and this function returns true.
If the request does not match any of this router's or its subrouters' routes then this function returns false. If available, a reason for the match failure will be filled in the match argument's MatchErr field. If the match failure type (eg: not found) has a registered handler, the handler is assigned to the Handler field of the match argument.
func (*Router) MatcherFunc ¶
func (r *Router) MatcherFunc(f MatcherFunc) *Route
MatcherFunc registers a new route with a custom matcher function. See Route.MatcherFunc().
func (*Router) Methods ¶
Methods registers a new route with a matcher for HTTP methods. See Route.Methods().
func (*Router) PathPrefix ¶
PathPrefix registers a new route with a matcher for the URL path prefix. See Route.PathPrefix().
func (*Router) Queries ¶
Queries registers a new route with a matcher for URL query values. See Route.Queries().
func (*Router) Schemes ¶
Schemes registers a new route with a matcher for URL schemes. See Route.Schemes().
func (*Router) ServeHTTP ¶
func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request)
ServeHTTP dispatches the handler registered in the matched route.
When there is a match, the route variables can be retrieved calling mux.Vars(request).
func (*Router) SkipClean ¶
SkipClean defines the path cleaning behaviour for new routes. The initial value is false. Users should be careful about which routes are not cleaned
When true, if the route path is "/path//to", it will remain with the double slash. This is helpful if you have a route like: /fetch/http://xkcd.com/534/
When false, the path will be cleaned, so /fetch/http://xkcd.com/534/ will become /fetch/http/xkcd.com/534
func (*Router) StrictSlash ¶
StrictSlash defines the trailing slash behavior for new routes. The initial value is false.
When true, if the route path is "/path/", accessing "/path" will perform a redirect to the former and vice versa. In other words, your application will always see the path as specified in the route.
When false, if the route path is "/path", accessing "/path/" will not match this route and vice versa.
The re-direct is a HTTP 301 (Moved Permanently). Note that when this is set for routes with a non-idempotent method (e.g. POST, PUT), the subsequent re-directed request will be made as a GET by most clients. Use middleware or client settings to modify this behaviour as needed.
Special case: when a route sets a path prefix using the PathPrefix() method, strict slash is ignored for that route because the redirect behavior can't be determined from a prefix alone. However, any subrouters created from that route inherit the original StrictSlash setting.
func (*Router) Use ¶ added in v1.6.1
func (r *Router) Use(mwf ...MiddlewareFunc)
Use appends a MiddlewareFunc to the chain. Middleware can be used to intercept or otherwise modify requests and/or responses, and are executed in the order that they are applied to the Router.
func (*Router) UseEncodedPath ¶
UseEncodedPath tells the router to match the encoded original path to the routes. For eg. "/path/foo%2Fbar/to" will match the path "/path/{var}/to".
If not called, the router will match the unencoded path to the routes. For eg. "/path/foo%2Fbar/to" will match the path "/path/foo/bar/to"
Source Files