restful-filters.go

package main

import (
	"log"
	"net/http"
	"time"

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

type User struct {
	Id, Name string
}

type UserList struct {
	Users []User
}

// This example show how to create and use the three different Filters (Container,WebService and Route)
// When applied to the restful.DefaultContainer, we refer to them as a global filter.
//
// GET  http://localhost:8080/users/42
// and see the logging per filter (try repeating this request)

func main() {
	// install a global (=DefaultContainer) filter (processed before any webservice in the DefaultContainer)
	restful.Filter(globalLogging)

	restful.Add(NewUserService())
	log.Print("start listening on localhost:8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

func NewUserService() *restful.WebService {
	ws := new(restful.WebService)
	ws.
		Path("/users").
		Consumes(restful.MIME_XML, restful.MIME_JSON).
		Produces(restful.MIME_JSON, restful.MIME_XML)

	// install a webservice filter (processed before any route)
	ws.Filter(webserviceLogging).Filter(measureTime)

	// install a counter filter
	ws.Route(ws.GET("").Filter(NewCountFilter().routeCounter).To(getAllUsers))

	// install 2 chained route filters (processed before calling findUser)
	ws.Route(ws.GET("/{user-id}").Filter(routeLogging).Filter(NewCountFilter().routeCounter).To(findUser))
	return ws
}

// Global Filter
func globalLogging(req *restful.Request, resp *restful.Response, chain *restful.FilterChain) {
	log.Printf("[global-filter (logger)] %s,%s\n", req.Request.Method, req.Request.URL)
	chain.ProcessFilter(req, resp)
}

// WebService Filter
func webserviceLogging(req *restful.Request, resp *restful.Response, chain *restful.FilterChain) {
	log.Printf("[webservice-filter (logger)] %s,%s\n", req.Request.Method, req.Request.URL)
	chain.ProcessFilter(req, resp)
}

// WebService (post-process) Filter (as a struct that defines a FilterFunction)
func measureTime(req *restful.Request, resp *restful.Response, chain *restful.FilterChain) {
	now := time.Now()
	chain.ProcessFilter(req, resp)
	log.Printf("[webservice-filter (timer)] %v\n", time.Now().Sub(now))
}

// Route Filter (defines FilterFunction)
func routeLogging(req *restful.Request, resp *restful.Response, chain *restful.FilterChain) {
	log.Printf("[route-filter (logger)] %s,%s\n", req.Request.Method, req.Request.URL)
	chain.ProcessFilter(req, resp)
}

// Route Filter (as a struct that defines a FilterFunction)
// CountFilter implements a FilterFunction for counting requests.
type CountFilter struct {
	count   int
	counter chan int // for go-routine safe count increments
}

// NewCountFilter creates and initializes a new CountFilter.
func NewCountFilter() *CountFilter {
	c := new(CountFilter)
	c.counter = make(chan int)
	go func() {
		for {
			c.count += <-c.counter
		}
	}()
	return c
}

// routeCounter increments the count of the filter (through a channel)
func (c *CountFilter) routeCounter(req *restful.Request, resp *restful.Response, chain *restful.FilterChain) {
	c.counter <- 1
	log.Printf("[route-filter (counter)] count:%d", c.count)
	chain.ProcessFilter(req, resp)
}

// GET http://localhost:8080/users
//
func getAllUsers(request *restful.Request, response *restful.Response) {
	log.Print("getAllUsers")
	response.WriteEntity(UserList{[]User{{"42", "Gandalf"}, {"3.14", "Pi"}}})
}

// GET http://localhost:8080/users/42
//
func findUser(request *restful.Request, response *restful.Response) {
	log.Print("findUser")
	response.WriteEntity(User{"42", "Gandalf"})
}