Lion

Lion is a fast HTTP router for Go with support for middlewares for building modern scalable modular REST APIs.

Features

• Context-Aware: Lion uses the de-facto standard net/Context for storing route params and sharing variables between middlewares and HTTP handlers. It could be integrated in the standard library for Go 1.7 in 2016.
• Modular: You can define your own modules to easily build a scalable architecture
• REST friendly: You can define modules to groups http resources together.
• Host: Match hosts. Each host can get its own content.
• Zero allocations: Lion generates zero garbage*.

Table of contents

• Install/Update
• Hello World
• Getting started with modules and resources
• Handlers
  • Using Handlers
  • Using HandlerFuncs
  • Using native http.Handler
  • Using native http.Handler with lion.Wrap()
  • Using native http.Handler with lion.WrapFunc()
• Middlewares
  • Using Named Middlewares
  • Using Negroni Middlewares
• Match Hosts
• Resources
• Examples
  • Using GET, POST, PUT, DELETE http methods
  • Using middlewares
  • Group routes by a base path
  • Mounting a router into a base path
  • Default middlewares
• Custom Middlewares
  • Custom Logger example
• Benchmarks
• License
• Todo
• Credits

Install/Update

$ go get -u github.com/celrenheit/lion

Hello World

package main

import (
    "fmt"
    "net/http"

    "github.com/celrenheit/lion"
    "golang.org/x/net/context"
)

func Home(c context.Context, w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Home")
}

func Hello(c context.Context, w http.ResponseWriter, r *http.Request) {
    name := lion.Param(c, "name")
    fmt.Fprintf(w, "Hello "+name)
}

func main() {
    l := lion.Classic()
    l.GetFunc("/", Home)
    l.GetFunc("/hello/:name", Hello)
    l.Run()
}

Try it yourself by running the following command from the current directory:

$ go run examples/hello/hello.go

Getting started with modules and resources

We are going to build a sample products listing REST api (without database handling to keep it simple):

func main() {
    l := lion.Classic()
    api := l.Group("/api")
    api.Module(Products{})
    l.Run()
}

// Products module is accessible at url: /api/products
// It handles getting a list of products or creating a new product
type Products struct{}

func (p Products) Base() string {
    return "/products"
}

func (p Products) Get(c context.Context, w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Fetching all products")
}

func (p Products) Post(c context.Context, w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Creating a new product")
}

func (p Products) Routes(r *lion.Router) {
    // Defining a resource for getting, editing and deleting a single product
    r.Resource("/:id", OneProduct{})
}

// OneProduct resource is accessible at url: /api/products/:id
// It handles getting, editing and deleting a single product
type OneProduct struct{}

func (p OneProduct) Get(c context.Context, w http.ResponseWriter, r *http.Request) {
    id := lion.Param(c, "id")
    fmt.Fprintf(w, "Getting product: %s", id)
}

func (p OneProduct) Put(c context.Context, w http.ResponseWriter, r *http.Request) {
    id := lion.Param(c, "id")
    fmt.Fprintf(w, "Updating article: %s", id)
}

func (p OneProduct) Delete(c context.Context, w http.ResponseWriter, r *http.Request) {
    id := lion.Param(c, "id")
    fmt.Fprintf(w, "Deleting article: %s", id)
}

Try it yourself. Run:

$ go run examples/modular-hello/modular-hello.go

Open your web browser to http://localhost:3000/api/products or http://localhost:3000/api/products/123. You should see "Fetching all products" or "Getting product: 123".

Handlers

Handlers should implement the Handler interface:

type Handler interface {
    ServeHTTPC(context.Context, http.ResponseWriter, *http.Request)
}

Using Handlers

l.Get("/get", get)
l.Post("/post", post)
l.Put("/put", put)
l.Delete("/delete", delete)

Using HandlerFuncs

HandlerFuncs shoud have this function signature:

func handlerFunc(c context.Context, w http.ResponseWriter, r *http.Request)  {
  fmt.Fprintf(w, "Hi!")
}

l.GetFunc("/get", handlerFunc)
l.PostFunc("/post", handlerFunc)
l.PutFunc("/put", handlerFunc)
l.DeleteFunc("/delete", handlerFunc)

Using native http.Handler

type nativehandler struct {}

func (_ nativehandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {

}

l.GetH("/somepath", nativehandler{})
l.PostH("/somepath", nativehandler{})
l.PutH("/somepath", nativehandler{})
l.DeleteH("/somepath", nativehandler{})

Using native http.Handler with lion.Wrap()

Note: using native http handler you cannot access url params.

func main() {
    l := lion.New()
    l.Get("/somepath", lion.Wrap(nativehandler{}))
}

Using native http.Handler with lion.WrapFunc()

func getHandlerFunc(w http.ResponseWriter, r *http.Request) {

}

func main() {
    l := lion.New()
    l.Get("/somepath", lion.WrapFunc(getHandlerFunc))
}

Middlewares

Middlewares should implement the Middleware interface:

type Middleware interface {
    ServeNext(Handler) Handler
}

The ServeNext function accepts a Handler and returns a Handler.

You can also use MiddlewareFuncs. For example:

func middlewareFunc(next Handler) Handler  {
    return next
}

Using Named Middlewares

Named middlewares are designed to be able to reuse a previously defined middleware. For example, if you have a EnsureAuthenticated middleware that check whether a user is logged in. You can define it once and reuse later in your application.

l := lion.New()
l.Define("EnsureAuthenticated", NewEnsureAuthenticatedMiddleware())

To reuse it later in your application, you can use the UseNamed method. If it cannot find the named middleware if the current Router instance it will try to find it in the parent router. If a named middleware is not found it will panic.

api := l.Group("/api")
api.UseNamed("EnsureAuthenticated")

Using Negroni Middlewares

You can use Negroni middlewares you can find a list of third party middlewares here

l := lion.New()
l.UseNegroni(negroni.NewRecovery())
l.Run()

Matching Hosts

You can match a specific or multiple hosts. You can use patterns in the same way they are currently used for routes with only some edge cases. The main difference is that you will have to use the '$' character instead of ':' to define a parameter.

admin.example.com will match admin.example.com $username.blog.com will match messi.blog.com will not match my.awesome.blog.com *.example.com will match my.admin.example.com

l := New()

// Group by /api basepath
api := l.Group("/api")

// Specific to v1
v1 := api.Subrouter().
    Host("v1.example.org")

v1.Get("/", v1Handler)

// Specific to v2
v2 := api.Subrouter().
    Host("v2.example.org")

v2.Get("/", v2Handler)
l.Run()

Resources

You can define a resource to represent a REST, CRUD api resource. You define global middlewares using Uses() method. For defining custom middlewares for each http method, you have to create a function which name is composed of the http method suffixed by "Middlewares". For example, if you want to define middlewares for the Get method you will have to create a method called: GetMiddlewares().

A resource is defined by the following methods. Everything is optional:

// Global middlewares for the resource (Optional)
Uses() Middlewares

// Middlewares for the http methods (Optional)
GetMiddlewares() Middlewares
PostMiddlewares() Middlewares
PutMiddlewares() Middlewares
DeleteMiddlewares() Middlewares


// HandlerFuncs for each HTTP Methods (Optional)
Get(c context.Context, w http.ResponseWriter, r *http.Request)
Post(c context.Context, w http.ResponseWriter, r *http.Request)
Put(c context.Context, w http.ResponseWriter, r *http.Request)
Delete(c context.Context, w http.ResponseWriter, r *http.Request)

Example:

package main

type todolist struct{}

func (t todolist) Uses() lion.Middlewares {
    return lion.Middlewares{lion.NewLogger()}
}

func (t todolist) Get(c context.Context, w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "getting todos")
}

func main() {
    l := lion.New()
    l.Resource("/todos", todolist{})
    l.Run()
}

Modules

Modules are a way to modularize an api which can then define submodules, subresources and custom routes. A module is defined by the following methods:

// Required: Base url pattern of the module
Base() string

// Routes accepts a Router instance. This method is used to define the routes of this module.
// Each routes defined are relative to the Base() url pattern
Routes(*Router)

// Optional: Requires named middlewares. Refer to Named Middlewares section
Requires() []string

package main

type api struct{}

// Required: Base url
func (t api) Base() string { return "/api" }

// Required: Here you can declare sub-resources, submodules and custom routes.
func (t api) Routes(r *lion.Router) {
    r.Module(v1{})
    r.Get("/custom", t.CustomRoute)
}

// Optional: Attach Get method to this Module.
// ====> A Module is also a Resource.
func (t api) Get(c context.Context, w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "This also a resource accessible at http://localhost:3000/api")
}

// Optional: Defining custom routes
func (t api) CustomRoute(c context.Context, w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "This a custom route for this module http://localhost:3000/api/")
}

func main() {
    l := lion.New()
    // Registering the module
    l.Module(api{})
    l.Run()
}

Examples

Using GET, POST, PUT, DELETE http methods

l := lion.Classic()

// Using Handlers
l.Get("/get", get)
l.Post("/post", post)
l.Put("/put", put)
l.Delete("/delete", delete)

// Using functions
l.GetFunc("/get", getFunc)
l.PostFunc("/post", postFunc)
l.PutFunc("/put", putFunc)
l.DeleteFunc("/delete", deleteFunc)

l.Run()

Using middlewares

func main() {
    l := lion.Classic()

    // Using middleware
    l.Use(lion.NewLogger())

    // Using middleware functions
    l.UseFunc(someMiddlewareFunc)

    l.GetFunc("/hello/:name", Hello)

    l.Run()
}

Group routes by a base path

l := lion.Classic()
api := l.Group("/api")

v1 := l.Group("/v1")
v1.GetFunc("/somepath", gettingFromV1)

v2 := l.Group("/v2")
v2.GetFunc("/somepath", gettingFromV2)

l.Run()

Mounting a router into a base path

l := lion.Classic()

sub := lion.New()
sub.GetFunc("/somepath", getting)


l.Mount("/api", sub)

Default middlewares

lion.Classic() creates a router with default middlewares (Recovery, RealIP, Logger, Static). If you wish to create a blank router without any middlewares you can use lion.New().

func main()  {
    // This a no middlewares registered
    l := lion.New()
    l.Use(lion.NewLogger())

    l.GetFunc("/hello/:name", Hello)

    l.Run()
}

Custom Middlewares

Custom middlewares should implement the Middleware interface:

type Middleware interface {
    ServeNext(Handler) Handler
}

You can also make MiddlewareFuncs to use using .UseFunc() method. It has to accept a Handler and return a Handler:

func(next Handler) Handler

Custom Logger example

type logger struct{}

func (*logger) ServeNext(next lion.Handler) lion.Handler {
    return lion.HandlerFunc(func(c context.Context, w http.ResponseWriter, r *http.Request) {
        start := time.Now()

        next.ServeHTTPC(c, w, r)

        fmt.Printf("Served %s in %s\n", r.URL.Path, time.Since(start))
    })
}

Then in the main function you can use the middleware using:

l := lion.New()

l.Use(&logger{})
l.GetFunc("/hello/:name", Hello)
l.Run()

Benchmarks

Without path cleaning

``` BenchmarkLion_Param 10000000 164 ns/op 0 B/op 0 allocs/op BenchmarkLion_Param5 5000000 372 ns/op 0 B/op 0 allocs/op BenchmarkLion_Param20 1000000 1080 ns/op 0 B/op 0 allo