restful-CORS-filter.go

package main

import (
	"io"
	"log"
	"net/http"

	restful "github.com/emicklei/go-restful/v3"
)

// Cross-origin resource sharing (CORS) is a mechanism that allows JavaScript on a web page
// to make XMLHttpRequests to another domain, not the domain the JavaScript originated from.
//
// http://en.wikipedia.org/wiki/Cross-origin_resource_sharing
// http://enable-cors.org/server.html
//
// GET http://localhost:8080/users
//
// GET http://localhost:8080/users/1
//
// PUT http://localhost:8080/users/1
//
// DELETE http://localhost:8080/users/1
//
// OPTIONS http://localhost:8080/users/1  with Header "Origin" set to some domain and

type UserResource struct{}

func (u UserResource) RegisterTo(container *restful.Container) {
	ws := new(restful.WebService)
	ws.
		Path("/users").
		Consumes("*/*").
		Produces("*/*")

	ws.Route(ws.GET("/{user-id}").To(u.nop))
	ws.Route(ws.POST("").To(u.nop))
	ws.Route(ws.PUT("/{user-id}").To(u.nop))
	ws.Route(ws.DELETE("/{user-id}").To(u.nop))

	container.Add(ws)
}

func (u UserResource) nop(request *restful.Request, response *restful.Response) {
	io.WriteString(response.ResponseWriter, "this would be a normal response")
}

func main() {
	wsContainer := restful.NewContainer()
	u := UserResource{}
	u.RegisterTo(wsContainer)

	// Add container filter to enable CORS
	cors := restful.CrossOriginResourceSharing{
		ExposeHeaders:  []string{"X-My-Header"},
		AllowedHeaders: []string{"Content-Type", "Accept"},
		AllowedMethods: []string{"GET", "POST"},
		CookiesAllowed: false,
		Container:      wsContainer}
	wsContainer.Filter(cors.Filter)

	// Add container filter to respond to OPTIONS
	wsContainer.Filter(wsContainer.OPTIONSFilter)

	log.Print("start listening on localhost:8080")
	server := &http.Server{Addr: ":8080", Handler: wsContainer}
	log.Fatal(server.ListenAndServe())
}