middleware.go

Documentation: github.com/gorilla/mux

     1  package mux
     2  
     3  import (
     4  	"net/http"
     5  	"strings"
     6  )
     7  
     8  // MiddlewareFunc is a function which receives an http.Handler and returns another http.Handler.
     9  // Typically, the returned handler is a closure which does something with the http.ResponseWriter and http.Request passed
    10  // to it, and then calls the handler passed as parameter to the MiddlewareFunc.
    11  type MiddlewareFunc func(http.Handler) http.Handler
    12  
    13  // middleware interface is anything which implements a MiddlewareFunc named Middleware.
    14  type middleware interface {
    15  	Middleware(handler http.Handler) http.Handler
    16  }
    17  
    18  // Middleware allows MiddlewareFunc to implement the middleware interface.
    19  func (mw MiddlewareFunc) Middleware(handler http.Handler) http.Handler {
    20  	return mw(handler)
    21  }
    22  
    23  // 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.
    24  func (r *Router) Use(mwf ...MiddlewareFunc) {
    25  	for _, fn := range mwf {
    26  		r.middlewares = append(r.middlewares, fn)
    27  	}
    28  }
    29  
    30  // useInterface appends a middleware 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.
    31  func (r *Router) useInterface(mw middleware) {
    32  	r.middlewares = append(r.middlewares, mw)
    33  }
    34  
    35  // CORSMethodMiddleware automatically sets the Access-Control-Allow-Methods response header
    36  // on requests for routes that have an OPTIONS method matcher to all the method matchers on
    37  // the route. Routes that do not explicitly handle OPTIONS requests will not be processed
    38  // by the middleware. See examples for usage.
    39  func CORSMethodMiddleware(r *Router) MiddlewareFunc {
    40  	return func(next http.Handler) http.Handler {
    41  		return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
    42  			allMethods, err := getAllMethodsForRoute(r, req)
    43  			if err == nil {
    44  				for _, v := range allMethods {
    45  					if v == http.MethodOptions {
    46  						w.Header().Set("Access-Control-Allow-Methods", strings.Join(allMethods, ","))
    47  					}
    48  				}
    49  			}
    50  
    51  			next.ServeHTTP(w, req)
    52  		})
    53  	}
    54  }
    55  
    56  // getAllMethodsForRoute returns all the methods from method matchers matching a given
    57  // request.
    58  func getAllMethodsForRoute(r *Router, req *http.Request) ([]string, error) {
    59  	var allMethods []string
    60  
    61  	for _, route := range r.routes {
    62  		var match RouteMatch
    63  		if route.Match(req, &match) || match.MatchErr == ErrMethodMismatch {
    64  			methods, err := route.GetMethods()
    65  			if err != nil {
    66  				return nil, err
    67  			}
    68  
    69  			allMethods = append(allMethods, methods...)
    70  		}
    71  	}
    72  
    73  	return allMethods, nil
    74  }
    75
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