Martini

Martini is a powerful package for quickly writing modular web applications/services in Golang.

Getting Started

After installing Go and setting up your GOPATH, create your first .go file. We'll call it server.go.

package main

import "github.com/codegangsta/martini"

func main() {
  m := martini.Classic()
  m.Get("/", func() string {
    return "Hello world!"
  })
  m.Run()
}

Then install the Martini package (go 1.1 and greater is required):

go get github.com/codegangsta/martini

Then run your server:

go run server.go

You will now have a Martini webserver running on localhost:3000.

Getting Help

Join the Mailing list

Watch the Demo Video

Features

• Extremely simple to use.
• Non-intrusive design.
• Play nice with other Golang packages.
• Awesome path matching and routing.
• Modular design - Easy to add functionality, easy to rip stuff out.
• Lots of good handlers/middlewares to use.
• Great 'out of the box' feature set.
• Fully compatible with the http.HandlerFunc interface.

More Middleware

For more middleware and functionality, check out the martini-contrib repository.

Table of Contents

• Classic Martini
  • Handlers
  • Routing
  • Services
  • Serving Static Files
• Middleware Handlers
  • Next()
• FAQ

Classic Martini

To get up and running quickly, martini.Classic() provides some reasonable defaults that work well for most web applications:

  m := martini.Classic()
  // ... middleware and routing goes here
  m.Run()

Below is some of the functionality martini.Classic() pulls in automatically:

• Request/Response Logging - martini.Logger
• Panic Recovery - martini.Recovery
• Static File serving - martini.Static
• Routing - martini.Router

Handlers

Handlers are the heart and soul of Martini. A handler is basically any kind of callable function:

m.Get("/", func() {
  println("hello world")
})

Return Values

If a handler returns something, Martini will write the result to the current http.ResponseWriter as a string:

m.Get("/", func() string {
  return "hello world" // HTTP 200 : "hello world"
})

You can also optionally return a status code:

m.Get("/", func() (int, string) {
  return 418, "i'm a teapot" // HTTP 418 : "i'm a teapot"
})

Service Injection

Handlers are invoked via reflection. Martini makes use of Dependency Injection to resolve dependencies in a Handlers argument list. This makes Martini completely compatible with golang's http.HandlerFunc interface.

If you add an argument to your Handler, Martini will search it's list of services and attempt to resolve the dependency via type assertion:

m.Get("/", func(res http.ResponseWriter, req *http.Request) { // res and req are injected by Martini
  res.WriteHeader(200) // HTTP 200
})

The following services are included with martini.Classic():

• *log.Logger - Global logger for Martini.
• martini.Context - http request context.
• martini.Params - map[string]string of named params found by route matching.
• martini.Routes - Route helper service.
• http.ResponseWriter - http Response writer interface.
• *http.Request - http Request.

Routing

In Martini, a route is an HTTP method paired with a URL-matching pattern. Each route can take one or more handler methods:

m.Get("/", func() {
  // show something
})

m.Patch("/", func() {
  // update something
})

m.Post("/", func() {
  // create something
})

m.Put("/", func() {
  // replace something
})

m.Delete("/", func() {
  // destroy something
})

m.NotFound(func() {
  // handle 404
})

Routes are matched in the order they are defined. The first route that matches the request is invoked.

Route patterns may include named parameters, accessible via the martini.Params service:

m.Get("/hello/:name", func(params martini.Params) string {
  return "Hello " + params["name"]
})

Routes can be matched with regular expressions and globs as well:

m.Get("/hello/**", func(params martini.Params) string {
  return "Hello " + params["_1"]
})

Route handlers can be stacked on top of each other, which is useful for things like authentication and authorization:

m.Get("/secret", authorize, func() {
  // this will execute as long as authorize doesn't write a response
})

Services

Services are objects that are available to be injected into a Handler's argument list. You can map a service on a Global or Request level.

Global Mapping

A Martini instance implements the inject.Injector interface, so mapping a service is easy:

db := &MyDatabase{}
m := martini.Classic()
m.Map(db) // the service will be available to all handlers as *MyDatabase
// ...
m.Run()

Request-Level Mapping

Mapping on the request level can be done in a handler via martini.Context:

func MyCustomLoggerHandler(c martini.Context, req *http.Request) {
  logger := &MyCustomLogger{req}
  c.Map(logger) // mapped as *MyCustomLogger
}

Mapping values to Interfaces

One of the most powerful parts about services is the ability to map a service to an interface. For instance, if you wanted to override the http.ResponseWriter with an object that wrapped it and performed extra operations, you can write the following handler:

func WrapResponseWriter(res http.ResponseWriter, c martini.Context) {
  rw := NewSpecialResponseWriter(res)
  c.MapTo(rw, (*http.ResponseWriter)(nil)) // override ResponseWriter with our wrapper ResponseWriter
}

Serving Static Files

A martini.Classic() instance automatically serves static files from the "public" directory in the root of your server. You can serve from more directories by adding more martini.Static handlers.

m.Use(martini.Static("assets")) // serve from the "assets" directory as well

Middleware Handlers

Middleware Handlers sit between the incoming http request and the router. In essence they are no different than any other Handler in Martini. You can add a middleware handler to the stack like so:

m.Use(func() {
  // do some middleware stuff
})

You can have full control over the middleware stack with the Handlers function:

m.Handlers(
  Middleware1,
  Middleware2,
  Middleware3,
)

Middleware Handlers work really well for things like logging, authorization, authentication, sessions, gzipping, error pages and any other operations that must happen before or after an http request:

// validate an api key
m.Use(func(res http.ResponseWriter, req *http.Request) {
  if req.Header.Get("X-API-KEY") != "secret123" {
    res.WriteHeader(http.StatusUnauthorized)
  }
})

Next()

Context.Next() is an optional function that Middleware Handlers can call to yield the until after the other Handlers have been executed. This works really well for any operations that must happen after an http request:

// log before and after a request
m.Use(func(c martini.Context, log *log.Logger){
  log.Println("before a request")

  c.Next()
  
  log.Println("after a request")
})

FAQ

Where do I find middleware X?

Start by looking in the martini-contrib package. If it is not there feel free to put up a Pull Request for one.

How do I integrate with existing servers?

A Martini instance implements http.Handler, so it can easily be used to serve subtrees on existing Go servers. For example this is a working Martini app for Google App Engine:

package hello

import (
  "net/http"
  "github.com/codegangsta/martini"
)

func init() {
  m := martini.Classic()
  m.Get("/", func() string {
    return "Hello world!"
  })
  http.Handle("/", m)
}

How do I change the port/host?

Martini's Run function looks for the PORT environment variable and uses that. Otherwise Martini will default to port 3000. To have more flexibility over port and host, use the http.ListenAndServe function instead.

  m := martini.Classic()
  // ...
  http.ListenAndServe(":8080", m)

Contributing

Martini is meant to be kept tiny and clean. Most contributions should end up in the martini-contrib repository. If you do have a contribution for the core of Martini feel free to put up a Pull Request.

About

Martini is obsessively designed by none other than the Code Gangsta