provisioner/vendor/github.com/gorilla/mux/doc.go - maas - Gitiles

 // Copyright 2012 The Gorilla Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 /*
 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")
 */
 package mux
	// Copyright 2012 The Gorilla Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	/*
	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")
	*/
	package mux