Sharing a gorilla/mux router across packages - go

I'm having some issues with implementing a slight MVC design with gorilla/mux.
The layout of the modules is as follows:
main.go
-- controllers
---- base.controller.go
---- example.controller.go
-- models
---- base.model.go
---- example.controller.go
All the files in controllers is in the controllers package, same with models and then the main.go is the main package.
Currently I'm just trying to get the Base Controller to be able to be shared with the main package which is working, although it's throwing some errors when trying to implement routes. The build is not throwing any errors, but the routes are not available. If I implement the Walk function in the Gorilla/Mux documentation to print out all the registered routes for the mux.Router then it gives me this error:
&{%!!(MISSING)s(*mux.Router=&{ [0xc4200901b0] map[] true
false false false}) %!!(MISSING)s(http.HandlerFunc=0xc8df0)
[%!!(MISSING)s(*mux.routeRegexp=&{/ false false true false
0xc420095360 / [] []})] %!!(MISSING)s(*mux.routeRegexpGroup=&{
0xc420016240 []}) %!!(MISSING)s(bool=true) %!!(MISSING)s(bool=false)
%!!(MISSING)s(bool=false) %!!(MISSING)s(bool=false)
%!!(MISSING)s(mux.BuildVarsFunc=)}
The reasoning for the global var V1Router *mux.Router is firstly to access it in the main package and also to create subrouters in the other controllers.
I am fairly new to Go, but I'm trying my best to learn the best practices! Any help would be greatly appreciated!
Example code below:
base.controllers.go
package controllers
import (
"fmt"
"bytes"
"net/http"
"github.com/gorilla/mux"
)
var V1Router *mux.Router
func init () {
V1Router = mux.NewRouter()
V1Router.StrictSlash(true)
V1Router.HandleFunc("/", BaseHandler)
}
// Base route to access the API Documentation.
func BaseHandler (w http.ResponseWriter, r *http.Request) {
fmt.Fprint(w, "Hello, Gophers!")
}
main.go
package main
import (
"net/http"
"log"
"github.com/projectrepo/project/models"
"github.com/projectrepo/project/controllers"
"github.com/gorilla/mux"
)
func main () {
http.Handle("/v1", controllers.V1Router)
if err := http.ListenAndServe(":8000", nil); err != nil {
log.Fatal("Serving error.")
}
}
In response to the comments, I tried this solution with the same result:
package main
import (
"net/http"
"log"
"github.com/projectrepo/project/models"
"github.com/projectrepo/project/controllers"
"github.com/gorilla/mux"
)
func main () {
r := mux.NewRouter()
r.Handle("/v1", controllers.V1Router)
if err := http.ListenAndServe(":8000", r); err != nil {
log.Fatal("Serving error.")
}
}

Gorilla mux.Router is supposed to be used to create mapping between a set of predefined rules (e.g. host, path, protocol, scheme, etc...) and it's handler (http.Handler or http.HandlerFunc). Gorilla mux can be used to replace standard server mux. If you combine gorilla/mux with built in http server mux as your original question, i.e.
func main () {
http.Handle("/v1", controllers.V1Router)
if err := http.ListenAndServe(":8000", nil); err != nil {
log.Fatal("Serving error.")
}
}
what actually happen when a client access /v1 is controllers.V1Router will be called with request path /v1 passed to V1Router1. In the controllers.V1Router, you defined that / will be handled by BaseHandler. However, since incoming request path is /v1, it won't match to your routing table. If you want to define sub routing, you can do as follows (this is what I mean in first comment):
func main () {
r := mux.NewRouter()
v1 := r.PathPrefix("/v1").Subrouter()
controllers.RegisterHandlers(v1)
if err := http.ListenAndServe(":8000", r); err != nil {
log.Fatal("Serving error.")
}
}
Then in the controllers (base.controllers.go) define
//Register handlers and it's sub router
func RegisterHandlers(r *mux.Router) {
//base handler, i.e. /v1
r.StrictSlash(true)
r.HandleFunc("/", BaseHandler)
//example sub-router, i.e. /v1/example
ex := r.PathPrefix("/example").Subrouter()
ex.HandleFunc("/", ExampleHandler)
//other handlers...
}

Related

Override Function from Another Module in Golang

How do you override a function created in another module in Golang?
Module A
In one module I have the function NewPersonApiService, the full code is laid out as below:
package openapi
import (
"context"
"errors"
"net/http"
)
// PersonApiService is a service that implements the logic for the PersonApiServicer
// This service should implement the business logic for every endpoint for the PersonApi API.
// Include any external packages or services that will be required by this service.
type PersonApiService struct {
}
// NewPersonApiService creates a default api service
func NewPersonApiService() PersonApiServicer {
return &PersonApiService{}
}
// ShowPerson - Detail
func (s *PersonApiService) ShowPerson(ctx context.Context) (ImplResponse, error) {
// TODO - update ShowPerson with the required logic for this service method.
// Add api_person_service.go to the .openapi-generator-ignore to avoid overwriting this service implementation when updating open api generation.
//TODO: Uncomment the next line to return response Response(200, Person{}) or use other options such as http.Ok ...
//return Response(200, Person{}), nil
//TODO: Uncomment the next line to return response Response(0, Error{}) or use other options such as http.Ok ...
//return Response(0, Error{}), nil
return Response(http.StatusNotImplemented, nil), errors.New("ShowPerson method not implemented")
}
Module B
In a separate module I want to override this NewPersonApiService.
I can call this function in the other module by doing the following:
package main
import (
"log"
"net/http"
openapi "build/code/spec/src"
)
func main() {
log.Printf("Server started")
PersonApiService := openapi.NewPersonApiService()
PersonApiController := openapi.NewPersonApiController(PersonApiService)
router := openapi.NewRouter(PersonApiController)
log.Fatal(http.ListenAndServe(":8080", router))
}
But if I try to override the function I get compilation error, unresolved type for openapi, below is what I was attempting to do:
package main
import (
"context"
"log"
"net/http"
openapi "build/code/spec/src"
)
func main() {
log.Printf("Server started")
PersonApiService := openapi.NewPersonApiService()
PersonApiController := openapi.NewPersonApiController(PersonApiService)
router := openapi.NewRouter(PersonApiController)
log.Fatal(http.ListenAndServe(":8080", router))
}
func (s openapi.PersonApiService) ShowPerson(ctx context.Context) (openapi.ImplResponse, error) {
return openapi.Response(200, openapi.Person{}), nil
}
Below is an image of the compilation error
Additional Info:
I believe Module B is properly referencing Module A.
Module A's go.mod file reads as follows:
module build/code/spec
go 1.13
require github.com/go-chi/chi/v5 v5.0.3
Module B's go.mod file reads as follows:
module bakkt.com/boilerplate
go 1.19
replace build/code/spec => ./../build/generated/
require build/code/spec v0.0.0-00010101000000-000000000000
require github.com/go-chi/chi/v5 v5.0.3 // indirect
The solution was to implement the ShowPerson method in another module, you would need to create a new type that implements the PersonApiServicer interface and provides its own implementation of the ShowPerson method.
Running this in Module B worked and allowed me to change the response of the API call defined in Module A.
package main
import (
"context"
"log"
"net/http"
openapi "build/code/spec/src"
)
type MyPersonApiService struct{}
func NewMyPersonApiService() openapi.PersonApiServicer {
return &MyPersonApiService{}
}
func (s *MyPersonApiService) ShowPerson(ctx context.Context) (openapi.ImplResponse, error) {
// TODO: Add your own implementation of the ShowPerson method here.
// For example, you could retrieve a person's details and return them as follows:
person := openapi.Person{Id: 23, Name: "Vark Thins", Age: 20}
return openapi.Response(http.StatusOK, person), nil
}
func main() {
log.Printf("Server started")
PersonApiService := NewMyPersonApiService()
PersonApiController := openapi.NewPersonApiController(PersonApiService)
router := openapi.NewRouter(PersonApiController)
log.Fatal(http.ListenAndServe(":8080", router))
}

How in Golang use struct in other package file?

I am new in Golang and need some help.
As you can see in the code below I am tring to create REST API in Golang. I use mux (Gorilla Mux) and pq (PostgreSQL driver) as third party libraries. Don't want to use ORM.
Inside application.go file I have InitializeRoutes function with a list of all aviable routes. GetFactors function process one of these routes. I am tring to define GetFactors function logic in other file called factors.go. Inside factors.go file I want to use Application struct which was defined in application.go. How to make it correctly? Right now as you can see they are in different packages. For thats why factors.go file don't see Application struct.
Project structure:
main.go
application.go
controllers
factors.go
main.go:
package main
func main() {
application := Application{}
application.Initialization()
application.Run("localhost:8000")
}
application.go:
package main
import (
"database/sql"
"github.com/gorilla/mux"
"log"
"net/http"
"rest-api/configurations"
)
type Application struct {
Router *mux.Router
Database *sql.DB
}
func (application *Application) Initialization() {
var err error
application.Database, err = configurations.DatabaseConnection()
if err != nil {
log.Fatal(err)
}
application.Router = mux.NewRouter()
application.Router.StrictSlash(true)
application.InitializeRoutes()
}
func (application *Application) Run(address string) {
log.Fatal(http.ListenAndServe(address, application.Router))
}
func (application *Application) InitializeRoutes() {
application.Router.HandleFunc("/api/factors", application.GetFactors).Methods("GET")
// other code
}
controllers/factors.go:
package controllers
import (
"net/http"
)
func (application *Application) GetFactors(rw http.ResponseWriter, request *http.Request) {
// code
}
Well, finally I decided to redesign the project structure.
main.go
routes
routes.go
controllers
factors.go
models
factors.go
main.go:
import (
"your_project_name/routes"
)
func main() {
// code
router := mux.NewRouter()
routes.Use(router)
// code
}
routes/routes.go:
package routes
import (
"github.com/gorilla/mux"
"your_application_name/controllers"
)
func Use(router *mux.Router) {
router.HandleFunc("/api/factors", controllers.GetFactors).Methods("GET")
}
controllers/factors.go:
package controllers
var GetFactors = func(res http.ResponseWriter, req *http.Request) {
// code
}

Pass a reference to a Redis instance to a Gorilla/Mux Handler

I'm trying to get my hands dirty while playing with some Gorilla/Mux and Go-Redis but I'm facing a little implementation problem here.
Essentially I have a project structured like the following:
Where redismanager.go handles the initialization of a Redis Client:
package redismanager
import (
"fmt"
"github.com/go-redis/redis"
)
func InitRedisClient() redis.Client {
client := redis.NewClient(&redis.Options{
Addr : "localhost:6379",
Password: "",
DB : 0, //default
})
pong, err := client.Ping().Result()
if( err != nil ){
fmt.Println("Cannot Initialize Redis Client ", err)
}
fmt.Println("Redis Client Successfully Initialized . . .", pong)
return *client
}
Where main.go calls redismanager.InitRedisClient and initializes mux.Handlers:
package main
import (
"github.com/gorilla/mux"
"github.com/go-redis/redis"
"net/http"
"fmt"
"log"
"encoding/json"
"io/ioutil"
"../redismanager"
"../api"
)
type RedisInstance struct {
RInstance *redis.Client
}
func main() {
//Initialize Redis Client
client := redismanager.InitRedisClient()
//Get current redis instance to get passed to different Gorilla-Mux Handlers
redisHandler := &RedisInstance{RInstance:&client}
//Initialize Router Handlers
r := mux.NewRouter()
r.HandleFunc("/todo", redisHandler.AddTodoHandler).
Methods("POST")
fmt.Println("Listening on port :8000 . . .")
// Bind to a port and pass our router in
log.Fatal(http.ListenAndServe(":8000", r))
}
Now, I can easily define and let work properly AddTodoHandler in the same file like:
func (c *RedisInstance) AddTodoHandler(w http.ResponseWriter, r *http.Request) {
. . . doSomething
}
But, to make things a bit more modular, I'm trying to move all of these RouteHandlers inside their respective files in api package. In order to make that, I need to pass a reference to redisHandler but I'm having some difficulties when trying to make that with an Handler inside api package.
For instance, If in the main I add:
r.HandleFunc("/todo/{id}", api.GetTodoHandler(&client)).
Methods("GET")
with gettodo.go
package api
import (
"net/http"
"github.com/gorilla/mux"
"fmt"
"encoding/json"
"github.com/go-redis/redis"
)
func GetTodoHandler(c *RedisInstance) func (w http.ResponseWriter, r *http.Request) {
func (w http.ResponseWriter, r *http.Request) {
. . . doSomething
}
}
It works nicely.
I'm still pretty new to Go and haven't found any cleaner solution to that even after several researches and reads.
Is my approach correct or are there any better ones?
Write a function that converts a function with the Redis instance argument to an HTTP handler:
func redisHandler(c *RedisInstance,
f func(c *RedisInstance, w http.ResponseWriter, r *http.Request)) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { f(c, w, r) })
}
Write your API handlers like this:
func AddTodoHandler(c *RedisInstance, w http.ResponseWriter, r *http.Request) {
...
}
Add to the mux like this:
r.Handler("/todo", redisHandler(client, api.AddTodoHandler)).Methods("POST")
where client is the Redis instance.
I would recommend using an App struct which initializes DB and Routes. And all Redis methods will be called inside.
e.g. type App struct{Routes *mux.Router, DB *DB_TYPE}
And which will have App.initializeRoutes method.
type App struct {
Router *mux.Router
DB *redis.NewClient
}
func (a *App) Run(addr string) {
log.Fatal(http.ListenAndServe(":8000", a.Router))
}
func (a *App) Initialize(addr, password string, db int) error {
// Connect postgres
db, err := redis.NewClient(&redis.Options{
Addr: addr,
Password: password,
DB: db,
})
if err != nil {
return err
}
// Ping to connection
err = db.Ping()
if err != nil {
return err
}
// Set db in Model
a.DB = db
a.Router = mux.NewRouter()
a.initializeRoutes()
return nil
}
func (a *App) initializeRoutes() {
a.Router.HandleFunc("/todo", a.AddTodoHandler).Methods("POST")
a.Router.HandleFunc("/todo/{id}", a.GetTodoHandler).Methods("GET")
}
// AddTodoHandler has access to DB, in your case Redis
// you can replace the steps for Redis.
func (a *App) AddTodoHandler() {
//has access to DB
a.DB
}
Hope you get the point, you can even extract out the Model work into a separate Struct and then pass it inside func's
r.HandleFunc("/todo/{id}", redisHandler.api.GetTodoHandler).Methods("GET")
Your redisHandler, as defined in main, has no api field, so this naturally doesn't compile.
If you re-defined your RedisInstance type in the api package, and you defined the handler methods on that type in the method-specific files, then you can initialize your redisHandler using that api.RedisInstance type and you can delete the main.RedisInstance type definition:
package main
import (
"github.com/gorilla/mux"
"github.com/go-redis/redis"
"net/http"
"fmt"
"log"
"encoding/json"
"io/ioutil"
"../redismanager"
"../api"
)
func main() {
//Initialize Redis Client
client := redismanager.InitRedisClient()
//Get current redis instance to get passed to different Gorilla-Mux Handlers
redisHandler := &api.RedisInstance{RInstance:&client}
//Initialize Router Handlers
r := mux.NewRouter()
r.HandleFunc("/todo", redisHandler.AddTodoHandler).Methods("POST")
r.HandleFunc("/todo/{id}", redisHandler.GetTodoHandler).Methods("GET")
fmt.Println("Listening on port :8000 . . .")
// Bind to a port and pass our router in
log.Fatal(http.ListenAndServe(":8000", r))
}

How to pass arguments to router handlers in Golang using Gin web framework?

I'm using Gin, https://gin-gonic.github.io/gin/, to build a simple RESTful JSON API with Golang.
The routes are setup with something like this:
func testRouteHandler(c *gin.Context) {
// do smth
}
func main() {
router := gin.Default()
router.GET("/test", testRouteHandler)
router.Run(":8080")
}
My question is how can I pass down an argument to the testRouteHandler function? For example a common database connection could be something that one wants to reuse among routes.
Is the best way to have this in a global variable? Or is there some way in Go to pass along an extra variable to the testRouteHandler function? Are there optional arguments for functions in Go?
PS. I'm just getting started in learning Go, so could be something obvious that I'm missing :)
I would avoid stuffing 'application scoped' dependencies (e.g. a DB connection pool) into a request context. Your two 'easiest' options are:
Make it a global. This is OK for smaller projects, and *sql.DB is thread-safe.
Pass it explicitly in a closure so that the return type satisfies gin.HandlerFunc
e.g.
// SomeHandler returns a `func(*gin.Context)` to satisfy Gin's router methods
// db could turn into an 'Env' struct that encapsulates all of your
// app dependencies - e.g. DB, logger, env vars, etc.
func SomeHandler(db *sql.DB) gin.HandlerFunc {
fn := func(c *gin.Context) {
// Your handler code goes in here - e.g.
rows, err := db.Query(...)
c.String(200, results)
}
return gin.HandlerFunc(fn)
}
func main() {
db, err := sql.Open(...)
// handle the error
router := gin.Default()
router.GET("/test", SomeHandler(db))
router.Run(":8080")
}
Using the link i posted on comments, I have created a simple example.
package main
import (
"log"
"github.com/gin-gonic/gin"
"github.com/jinzhu/gorm"
_ "github.com/mattn/go-sqlite3"
)
// ApiMiddleware will add the db connection to the context
func ApiMiddleware(db gorm.DB) gin.HandlerFunc {
return func(c *gin.Context) {
c.Set("databaseConn", db)
c.Next()
}
}
func main() {
r := gin.New()
// In this example, I'll open the db connection here...
// In your code you would probably do it somewhere else
db, err := gorm.Open("sqlite3", "./example.db")
if err != nil {
log.Fatal(err)
}
r.Use(ApiMiddleware(db))
r.GET("/api", func(c *gin.Context) {
// Don't forget type assertion when getting the connection from context.
dbConn, ok := c.MustGet("databaseConn").(gorm.DB)
if !ok {
// handle error here...
}
// do your thing here...
})
r.Run(":8080")
}
This is just a simple POC. But i believe it's a start.
Hope it helps.
Late to the party, so far here is my proposal. Encapsulate methods into the object with private/public vars in it:
package main
import (
"log"
"github.com/gin-gonic/gin"
"github.com/jinzhu/gorm"
_ "github.com/mattn/go-sqlite3"
)
type HandlerA struct {
Db gorm.DB
}
func (this *HandlerA) Get(c *gin.Context) {
log.Info("[%#f]", this.Db)
// do your thing here...
}
func main() {
r := gin.New()
// Init, should be separate, but it's ok for this sample:
db, err := gorm.Open("sqlite3", "./example.db")
if err != nil {
log.Fatal(err)
}
Obj := new(HandlerA)
Obj.Db = db // Or init inside Object
r := gin.New()
Group := r.Group("api/v1/")
{
Group.GET("/storage", Obj.Get)
}
r.Run(":8080")
}
Handler closures are a good option, but that works best when the argument is used in that handler alone.
If you have route groups, or long handler chains, where the same argument is needed in multiple places, you should set values into the Gin context.
You can use function literals, or named functions that return gin.HandlerFunc to do that in a clean way.
Example injecting configs into a router group:
Middleware package:
func Configs(conf APIV1Config) gin.HandlerFunc {
return func(c *gin.Context) {
c.Set("configKey", conf) // key could be an unexported struct to ensure uniqueness
}
}
Router:
conf := APIV1Config{/* some api configs */}
// makes conf available to all routes in this group
g := r.Group("/api/v1", middleware.Configs(conf))
{
// ... routes that all need API V1 configs
}
This is also easily unit-testable. Assuming that you test the single handlers, you can set the necessary values into the mock context:
w := httptest.NewRecorder()
c, _ := gin.CreateTestContext(w)
c.Set("configKey", /* mock configs */)
apiV1FooHandler(c)
Now in the case of application-scoped dependencies (db connections, remote clients, ...), I agree that setting these directly into the Gin context is a poor solution.
What you should do then, is to inject providers into the Gin context, using the pattern outlined above:
Middleware package:
// provider could be an interface for easy mocking
func DBProvider(provider database.Provider) gin.HandlerFunc {
return func(c *gin.Context) {
c.Set("providerKey", provider)
}
}
Router:
dbProvider := /* init provider with db connection */
r.Use(DBProvider(dbProvider)) // global middleware
// or
g := r.Group("/users", DBProvider(dbProvider)) // users group only
Handler (you can greatly reduce the boilerplate code by putting these context getters in some helper function):
// helper function
func GetDB(c *gin.Context) *sql.DB {
provider := c.MustGet("providerKey").(database.Provider)
return provider.GetConn()
}
func createUserHandler(c *gin.Context) {
db := GetDB(c) // same in all other handlers
// ...
}
I like wildneuro's example but would do a one liner to setup the handler
package main
import (
"log"
"github.com/gin-gonic/gin"
"github.com/jinzhu/gorm"
_ "github.com/mattn/go-sqlite3"
)
type HandlerA struct {
Db gorm.DB
}
func (this *HandlerA) Get(c *gin.Context) {
log.Info("[%#f]", this.Db)
// do your thing here...
}
func main() {
r := gin.New()
// Init, should be separate, but it's ok for this sample:
db, err := gorm.Open("sqlite3", "./example.db")
if err != nil {
log.Fatal(err)
}
r := gin.New()
Group := r.Group("api/v1/")
{
Group.GET("/storage", (&HandlerA{Db: db}).Get)
}
r.Run(":8080")
}
Let me try to explain in detail so that you won't get confused.
Depending on the incoming route, you want to call a controller function. Lets say your incoming route is /books and your controller is BooksController
Your BooksController will try to fetch the books from the database and returns a response.
Now, you want this a handler within your BooksController so that you can access database.
I would do something like this. Let's assume that you are using dynamoDB and the aws sdk provides *dynamodb.DynamoDB. Depending on your db, change this variable.
Create a struct as below.
type serviceConnection struct {
db *dynamoDB.DynamoDB
// You can have all services declared here
// which you want to use it in your controller
}
In your main function, get the db connection information. Let's say you already have a function initDatabaseConnection which returns a handler to db, something like below.
db := initDatabaseConnection() -> returns *dynamodb.DynamoDB
Set db to a struct variable.
conn := new(serviceConnection)
conn.db = db
Call the gin request method with a receiver handler as below.
r := gin.Default()
r.GET("/books", conn.BooksController)
As you see, the gin handler is a controller method which has your struct instance as a receiver.
Now, create a controller method with serviceConnection struct receiver.
func (conn *serviceConnection) BooksController(c *gin.Context) {
books := getBooks(conn.db)
}
As you see here, you have access to all the serviceConnection struct variables and you can use them in your controller.
Alright, I have given you a simple example. It should work. You can extend it as per your need
func main() {
router := gin.Default()
router.GET("/test/:id/:name", testRouteHandler)
router.Run(":8080")
}
func testRouteHandler(c *gin.Context) {
id := c.Params.ByName("id")
name := c.Params.ByName("name")
}
Now you will have to call your handler as below
http://localhost:8080/test/1/myname

Is it possible to know what route is used in HandleFunc

I am using http.HandleFunc("/resource", resource.Handle) from the package net/http and I was wondering if there was a way to see what route (in this case /resource) is used to get you to resource.Handle? Or do I have to create a Mux for this?
I'd like to know this to extract the resource from the url path to do some magic with it...
Yes you can
The main points to do:
Use the DefaultServeMux used by the HandleFunc method.
Construct a fake http.Request
For Example:
package main
import (
"fmt"
"net/http"
"net/url"
)
func main() {
theUrl, err := url.Parse("/response")
if err != nil {
fmt.Println(err.Error())
return
}
http.HandleFunc("/response", func(w http.ResponseWriter, r *http.Request) {
})
handler, path := http.DefaultServeMux.Handler(&http.Request{Method: "GET", URL: theUrl})
fmt.Println(handler, path)
}
see this Go Playground
http://golang.org/pkg/net/http/#Request
Use request.URL.Path to get the path used to access the handler.

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