242 lines
7.8 KiB
Markdown
242 lines
7.8 KiB
Markdown
mux
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===
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[](https://godoc.org/github.com/gorilla/mux)
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[](https://travis-ci.org/gorilla/mux)
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http://www.gorillatoolkit.org/pkg/mux
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Package `gorilla/mux` implements a request router and dispatcher.
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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:
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* Requests can be matched based on URL host, path, path prefix, schemes, header and query values, HTTP methods or using custom matchers.
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* URL hosts and paths can have variables with an optional regular expression.
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* Registered URLs can be built, or "reversed", which helps maintaining references to resources.
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* 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.
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* It implements the `http.Handler` interface so it is compatible with the standard `http.ServeMux`.
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Let's start registering a couple of URL paths and handlers:
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```go
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func main() {
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r := mux.NewRouter()
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r.HandleFunc("/", HomeHandler)
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r.HandleFunc("/products", ProductsHandler)
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r.HandleFunc("/articles", ArticlesHandler)
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http.Handle("/", r)
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}
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```
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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.
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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:
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```go
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r := mux.NewRouter()
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r.HandleFunc("/products/{key}", ProductHandler)
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r.HandleFunc("/articles/{category}/", ArticlesCategoryHandler)
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r.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler)
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```
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The names are used to create a map of route variables which can be retrieved calling `mux.Vars()`:
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```go
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vars := mux.Vars(request)
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category := vars["category"]
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```
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And this is all you need to know about the basic usage. More advanced options are explained below.
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Routes can also be restricted to a domain or subdomain. Just define a host pattern to be matched. They can also have variables:
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```go
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r := mux.NewRouter()
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// Only matches if domain is "www.example.com".
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r.Host("www.example.com")
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// Matches a dynamic subdomain.
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r.Host("{subdomain:[a-z]+}.domain.com")
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```
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There are several other matchers that can be added. To match path prefixes:
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```go
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r.PathPrefix("/products/")
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```
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...or HTTP methods:
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```go
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r.Methods("GET", "POST")
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```
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...or URL schemes:
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```go
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r.Schemes("https")
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```
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...or header values:
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```go
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r.Headers("X-Requested-With", "XMLHttpRequest")
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```
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...or query values:
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```go
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r.Queries("key", "value")
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```
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...or to use a custom matcher function:
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```go
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r.MatcherFunc(func(r *http.Request, rm *RouteMatch) bool {
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return r.ProtoMajor == 0
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})
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```
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...and finally, it is possible to combine several matchers in a single route:
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```go
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r.HandleFunc("/products", ProductsHandler).
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Host("www.example.com").
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Methods("GET").
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Schemes("http")
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```
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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".
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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:
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```go
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r := mux.NewRouter()
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s := r.Host("www.example.com").Subrouter()
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```
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Then register routes in the subrouter:
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```go
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s.HandleFunc("/products/", ProductsHandler)
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s.HandleFunc("/products/{key}", ProductHandler)
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s.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler)
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```
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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.
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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.
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There's one more thing about subroutes. When a subrouter has a path prefix, the inner routes use it as base for their paths:
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```go
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r := mux.NewRouter()
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s := r.PathPrefix("/products").Subrouter()
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// "/products/"
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s.HandleFunc("/", ProductsHandler)
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// "/products/{key}/"
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s.HandleFunc("/{key}/", ProductHandler)
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// "/products/{key}/details"
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s.HandleFunc("/{key}/details", ProductDetailsHandler)
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```
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Now let's see how to build registered URLs.
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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:
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```go
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r := mux.NewRouter()
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r.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler).
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Name("article")
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```
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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:
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```go
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url, err := r.Get("article").URL("category", "technology", "id", "42")
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```
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...and the result will be a `url.URL` with the following path:
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```
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"/articles/technology/42"
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```
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This also works for host variables:
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```go
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r := mux.NewRouter()
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r.Host("{subdomain}.domain.com").
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Path("/articles/{category}/{id:[0-9]+}").
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HandlerFunc(ArticleHandler).
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Name("article")
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// url.String() will be "http://news.domain.com/articles/technology/42"
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url, err := r.Get("article").URL("subdomain", "news",
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"category", "technology",
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"id", "42")
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```
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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.
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Regex support also exists for matching Headers within a route. For example, we could do:
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```go
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r.HeadersRegexp("Content-Type", "application/(text|json)")
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```
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...and the route will match both requests with a Content-Type of `application/json` as well as `application/text`
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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:
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```go
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// "http://news.domain.com/"
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host, err := r.Get("article").URLHost("subdomain", "news")
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// "/articles/technology/42"
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path, err := r.Get("article").URLPath("category", "technology", "id", "42")
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```
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And if you use subrouters, host and path defined separately can be built as well:
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```go
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r := mux.NewRouter()
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s := r.Host("{subdomain}.domain.com").Subrouter()
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s.Path("/articles/{category}/{id:[0-9]+}").
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HandlerFunc(ArticleHandler).
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Name("article")
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// "http://news.domain.com/articles/technology/42"
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url, err := r.Get("article").URL("subdomain", "news",
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"category", "technology",
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"id", "42")
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```
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## Full Example
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Here's a complete, runnable example of a small `mux` based server:
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```go
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package main
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import (
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"net/http"
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"log"
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"github.com/gorilla/mux"
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)
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func YourHandler(w http.ResponseWriter, r *http.Request) {
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w.Write([]byte("Gorilla!\n"))
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}
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func main() {
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r := mux.NewRouter()
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// Routes consist of a path and a handler function.
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r.HandleFunc("/", YourHandler)
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// Bind to a port and pass our router in
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log.Fatal(http.ListenAndServe(":8000", r))
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}
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```
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## License
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BSD licensed. See the LICENSE file for details.
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