mux

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 Go to latest Published: Apr 20, 2018 License: Apache-2.0, BSD-3-Clause Imports: 10 Imported by: 0

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 and paths 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 variables: 

r := mux.NewRouter()
r.Host("{subdomain}.domain.com").
  Path("/articles/{category}/{id:[0-9]+}").
  HandlerFunc(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. 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")

Index

Constants

This section is empty.

Variables

View Source 
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 Vars 

func Vars(r *http.Request) map[string]string

Vars returns the route variables for the current request, if any.

Types

type BuildVarsFunc 

type BuildVarsFunc func(map[string]string) map[string]string

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 Route 

type Route struct {
	// contains filtered or unexported fields
}

Route stores information to match a request and build URLs.

func CurrentRoute 

func CurrentRoute(r *http.Request) *Route

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) BuildOnly 

func (r *Route) BuildOnly() *Route

BuildOnly sets the route to never match: it is only used to build URLs.

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) GetError 

func (r *Route) GetError() error

GetError returns an error resulted from building the route, if any.

func (*Route) GetHandler 

func (r *Route) GetHandler() http.Handler

GetHandler returns the handler for the route, if any.

func (*Route) GetHostTemplate 

func (r *Route) GetHostTemplate() (string, error)

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) GetName 

func (r *Route) GetName() string

GetName returns the name for the route, if any.

func (*Route) GetPathTemplate 

func (r *Route) GetPathTemplate() (string, error)

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) Handler 

func (r *Route) Handler(handler http.Handler) *Route

Handler sets a handler for the route.

func (*Route) HandlerFunc 

func (r *Route) HandlerFunc(f func(http.ResponseWriter, *http.Request)) *Route

HandlerFunc sets a handler function for the route.

func (*Route) Headers 

func (r *Route) Headers(pairs ...string) *Route

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 

func (r *Route) HeadersRegexp(pairs ...string) *Route

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. It the value is an empty string, it will match any value if the key is set.

func (*Route) Host 

func (r *Route) Host(tpl string) *Route

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 

func (r *Route) Methods(methods ...string) *Route

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 

func (r *Route) Name(name string) *Route

Name sets the name for the route, used to build URLs. If the name was registered already it will be overwritten.

func (*Route) Path 

func (r *Route) Path(tpl string) *Route

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 

func (r *Route) PathPrefix(tpl string) *Route

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 

func (r *Route) Queries(pairs ...string) *Route

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 

func (r *Route) Schemes(schemes ...string) *Route

Schemes adds a matcher for URL schemes. It accepts a sequence of schemes to be matched, e.g.: "http", "https".

func (*Route) SkipClean 

func (r *Route) SkipClean() bool

func (*Route) Subrouter 

func (r *Route) Subrouter() *Router

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 

func (r *Route) URL(pairs ...string) (*url.URL, error)

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.

func (*Route) URLHost 

func (r *Route) URLHost(pairs ...string) (*url.URL, error)

URLHost builds the host part of the URL for a route. See Route.URL().

The route must have a host defined.

func (*Route) URLPath 

func (r *Route) URLPath(pairs ...string) (*url.URL, error)

URLPath builds the path part of the URL for a route. See Route.URL().

The route must have a path defined.

type RouteMatch 

type RouteMatch struct {
	Route   *Route
	Handler http.Handler
	Vars    map[string]string
}

RouteMatch stores information about a matched route.

type Router 

type Router struct {
	// Configurable Handler to be used when no route matches.
	NotFoundHandler 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 NewRouter 

func NewRouter() *Router

NewRouter returns a new router instance.

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) Get 

func (r *Router) Get(name string) *Route

Get returns a route registered with the given name.

func (*Router) GetRoute 

func (r *Router) GetRoute(name string) *Route

GetRoute returns a route registered with the given name. This method was renamed to Get() and remains here for backwards compatibility.

func (*Router) Handle 

func (r *Router) Handle(path string, handler http.Handler) *Route

Handle registers a new route with a matcher for the URL path. See Route.Path() and Route.Handler().

func (*Router) HandleFunc 

func (r *Router) HandleFunc(path string, f func(http.ResponseWriter,
	*http.Request)) *Route

HandleFunc registers a new route with a matcher for the URL path. See Route.Path() and Route.HandlerFunc().

func (*Router) Headers 

func (r *Router) Headers(pairs ...string) *Route

Headers registers a new route with a matcher for request header values. See Route.Headers().

func (*Router) Host 

func (r *Router) Host(tpl string) *Route

Host registers a new route with a matcher for the URL host. See Route.Host().

func (*Router) Match 

func (r *Router) Match(req *http.Request, match *RouteMatch) bool

Match matches registered routes against the request.

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 

func (r *Router) Methods(methods ...string) *Route

Methods registers a new route with a matcher for HTTP methods. See Route.Methods().

func (*Router) NewRoute 

func (r *Router) NewRoute() *Route

NewRoute registers an empty route.

func (*Router) Path 

func (r *Router) Path(tpl string) *Route

Path registers a new route with a matcher for the URL path. See Route.Path().

func (*Router) PathPrefix 

func (r *Router) PathPrefix(tpl string) *Route

PathPrefix registers a new route with a matcher for the URL path prefix. See Route.PathPrefix().

func (*Router) Queries 

func (r *Router) Queries(pairs ...string) *Route

Queries registers a new route with a matcher for URL query values. See Route.Queries().

func (*Router) Schemes 

func (r *Router) Schemes(schemes ...string) *Route

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 

func (r *Router) SkipClean(value bool) *Router

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 

func (r *Router) StrictSlash(value bool) *Router

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 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.

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) UseEncodedPath 

func (r *Router) UseEncodedPath() *Router

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". This behavior has the drawback of needing to match routes against r.RequestURI instead of r.URL.Path. Any modifications (such as http.StripPrefix) to r.URL.Path will not affect routing when this flag is on and thus may induce unintended behavior.

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"

func (*Router) Walk 

func (r *Router) Walk(walkFn WalkFunc) error

Walk walks the router and all its sub-routers, calling walkFn for each route in the tree. The routes are walked in the order they were added. Sub-routers are explored depth-first.

type WalkFunc 

type WalkFunc func(route *Route, router *Router, ancestors []*Route) error

WalkFunc is the type of the function called for each route visited by Walk. At every invocation, it is given the current route, and the current router, and a list of ancestor routes that lead to the current route.

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