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December 13, 2018 16:39
HTTP Request Contexts in Go — Examples — http://elithrar.github.io/article/map-string-interface/
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| package main | |
| import ( | |
| "fmt" | |
| "log" | |
| "net/http" | |
| "github.com/gocraft/web" | |
| ) | |
| type Context struct { | |
| CSRFToken string | |
| User string | |
| } | |
| // Our middleware *and* handlers must be defined as methods on our context struct, | |
| // or accept the type as their first argument. This ties handlers/middlewares to our | |
| // particular application structure/design. | |
| func (c *Context) CSRFMiddleware(w web.ResponseWriter, r *web.Request, next web.NextMiddlewareFunc) { | |
| token, err := GenerateToken(r) | |
| if err != nil { | |
| http.Error(w, "No good!", http.StatusInternalServerError) | |
| return | |
| } | |
| c.CSRFToken = token | |
| next(w, r) | |
| } | |
| func (c *Context) ShowSignupForm(w web.ResponseWriter, r *web.Request) { | |
| // No need to type assert it: we know the type. | |
| // We can just use the value directly. | |
| fmt.Fprintf(w, "Our token is %v", c.CSRFToken) | |
| } | |
| func main() { | |
| router := web.New(Context{}).Middleware((*Context).CSRFMiddleware) | |
| router.Get("/signup", (*Context).ShowSignupForm) | |
| err := http.ListenAndServe(":8000", router) | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| } | |
| func GenerateToken(r *web.Request) (string, error) { | |
| return "our-fake-token", nil | |
| } |
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| package main | |
| import ( | |
| "errors" | |
| "fmt" | |
| "net/http" | |
| "github.com/zenazn/goji" | |
| "github.com/zenazn/goji/web" | |
| ) | |
| var ErrTypeNotPresent = errors.New("Expected type not present in the request context.") | |
| // A little simpler: we just need this for every *type* we store. | |
| func GetContextString(c web.C, key string) (string, error) { | |
| val, ok := c.Env[key].(string) | |
| if !ok { | |
| return "", ErrTypeNotPresent | |
| } | |
| return val, nil | |
| } | |
| // A bare-bones example | |
| func CSRFMiddleware(c *web.C, h http.Handler) http.Handler { | |
| fn := func(w http.ResponseWriter, r *http.Request) { | |
| maskedToken, err := GenerateToken(r) | |
| if err != nil { | |
| http.Error(w, "No good!", http.StatusInternalServerError) | |
| return | |
| } | |
| // Goji only allocates a map when you ask for it. | |
| if c.Env == nil { | |
| c.Env = make(map[string]interface{}) | |
| } | |
| // Not a global - a reference to the context map | |
| // is passed to our handlers explicitly. | |
| c.Env["csrf_token"] = maskedToken | |
| h.ServeHTTP(w, r) | |
| } | |
| return http.HandlerFunc(fn) | |
| } | |
| // Goji's web.HandlerFunc type is an extension of net/http's http.HandlerFunc, | |
| // except it also passes in a request context (aka web.C.Env) | |
| func ShowSignupForm(c web.C, w http.ResponseWriter, r *http.Request) { | |
| // We'll use our helper function so we don't have to type assert | |
| // the result in every handler. | |
| csrfToken, err := GetContextString(c, "csrf_token") | |
| if err != nil { | |
| http.Error(w, "No good!", http.StatusInternalServerError) | |
| return | |
| } | |
| // We can access this token in every handler we wrap with our | |
| // middleware. No need to set/get from a session multiple times per | |
| // request (which is slow!) | |
| fmt.Fprintf(w, "Our token is %v", csrfToken) | |
| } | |
| func main() { | |
| goji.Get("/signup", ShowSignupForm) | |
| goji.Use(CSRFMiddleware) | |
| goji.Serve() | |
| } | |
| func GenerateToken(r *http.Request) (string, error) { | |
| return "our-fake-token", nil | |
| } |
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| package main | |
| import ( | |
| "errors" | |
| "fmt" | |
| "net/http" | |
| "github.com/gorilla/context" | |
| ) | |
| type contextKey int | |
| // Define keys that support equality. | |
| const csrfKey contextKey = 0 | |
| const userKey contextKey = 1 | |
| var ErrCSRFTokenNotPresent = errors.New("CSRF token not present in the request context.") | |
| // We'll need a helper function like this for every key:type | |
| // combination we store in our context map else we repeat this | |
| // in every middleware/handler that needs to access the value. | |
| func GetCSRFToken(r *http.Request) (string, error) { | |
| val, ok := context.GetOk(r, csrfKey) | |
| if !ok { | |
| return "", ErrCSRFTokenNotPresent | |
| } | |
| token, ok := val.(string) | |
| if !ok { | |
| return "", ErrCSRFTokenNotPresent | |
| } | |
| return token, nil | |
| } | |
| // A bare-bones example | |
| func CSRFMiddleware(h http.Handler) http.Handler { | |
| fn := func(w http.ResponseWriter, r *http.Request) { | |
| // A minimal example: in reality, our CSRF middleware would | |
| // do a *lot* more than just this. | |
| maskedToken, err := GenerateToken(r) | |
| if err != nil { | |
| http.Error(w, "No good!", http.StatusInternalServerError) | |
| return | |
| } | |
| // The map is global, so we just call the Set function | |
| context.Set(r, csrfKey, maskedToken) | |
| h.ServeHTTP(w, r) | |
| } | |
| return http.HandlerFunc(fn) | |
| } | |
| func ShowSignupForm(w http.ResponseWriter, r *http.Request) { | |
| // We'll use our helper function so we don't have to type assert | |
| // the result in every handler that triggers/handles a POST request. | |
| csrfToken, err := GetCSRFToken(r) | |
| if err != nil { | |
| http.Error(w, "No good!", http.StatusInternalServerError) | |
| return | |
| } | |
| // We can access this token in every handler we wrap with our | |
| // middleware. No need to set/get from a session multiple times per | |
| // request (which is slow!) | |
| fmt.Fprintf(w, "Our token is %v", csrfToken) | |
| } | |
| func main() { | |
| r := http.NewServeMux() | |
| r.Handle("/signup", CSRFMiddleware(http.HandlerFunc(ShowSignupForm))) | |
| // Critical that we call context.ClearHandler here, else we leave | |
| // old requests in the map. | |
| err := http.ListenAndServe(":8000", context.ClearHandler(r)) | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| } | |
| func GenerateToken(r *http.Request) (string, error) { | |
| return "our-fake-token", nil | |
| } |
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You have not imported "log" in gorilla example: