Middleware

When we talk about Middleware in Iris we're talking about running code before and/or after our main handler code in a HTTP request lifecycle. For example, logging middleware might write the incoming request details to a log, then call the handler code, before writing details about the response to the log. One of the cool things about middleware is that these units are extremely flexible and reusable.

A middleware is just a Handler form of func(ctx iris.Context), the middleware is being executed when the previous middleware calls the ctx.Next(), this can be used for authentication, i.e: if logged in then ctx.Next() otherwise fire an error response.

Writing a middleware

package main

import "github.com/kataras/iris"

func main() {
    app := iris.New()
    app.Get("/", before, mainHandler, after)
    app.Run(iris.Addr(":8080"))
}

func before(ctx iris.Context) {
    shareInformation := "this is a sharable information between handlers"

    requestPath := ctx.Path()
    println("Before the mainHandler: " + requestPath)

    ctx.Values().Set("info", shareInformation)
    ctx.Next() // execute the next handler, in this case the main one.
}

func after(ctx iris.Context) {
    println("After the mainHandler")
}

func mainHandler(ctx iris.Context) {
    println("Inside mainHandler")

    // take the info from the "before" handler.
    info := ctx.Values().GetString("info")

    // write something to the client as a response.
    ctx.HTML("<h1>Response</h1>")
    ctx.HTML("<br/> Info: " + info)

    ctx.Next() // execute the "after".
}
$ go run main.go # and navigate to the http://localhost:8080
Now listening on: http://localhost:8080
Application started. Press CTRL+C to shut down.
Before the mainHandler: /
Inside mainHandler
After the mainHandler

Globally

package main

import "github.com/kataras/iris"

func main() {
    app := iris.New()
    // register the "before" handler as the first handler which will be executed
    // on all domain's routes.
    // or use the `UseGlobal` to register a middleware which will fire across subdomains.
    app.Use(before)
    // register the "after" handler as the last handler which will be executed
    // after all domain's routes' handler(s).
    app.Done(after)

    // register our routes.
    app.Get("/", indexHandler)
    app.Get("/contact", contactHandler)

    app.Run(iris.Addr(":8080"))
}

func before(ctx iris.Context) {
     // [...]
}

func after(ctx iris.Context) {
    // [...]
}

func indexHandler(ctx iris.Context) {
    // write something to the client as a response.
    ctx.HTML("<h1>Index</h1>")

    ctx.Next() // execute the "after" handler registered via `Done`.
}

func contactHandler(ctx iris.Context) {
    // write something to the client as a response.
    ctx.HTML("<h1>Contact</h1>")

    ctx.Next() // execute the "after" handler registered via `Done`.
}

Explore

Bellow you can see the source code of some useful handlers to learn of

Middleware Example
basic authentication iris/_examples/authentication/basicauth
Google reCAPTCHA iris/_examples/miscellaneous/recaptcha
localization and internationalization iris/_examples/miscellaneous/i81n
request logger iris/_examples/http_request/request-logger
profiling (pprof) iris/_examples/miscellaneous/pprof
recovery iris/_examples/miscellaneous/recover

Some middlewares that really helps you on specific tasks

Middleware Description Example
jwt Middleware checks for a JWT on the Authorization header on incoming requests and decodes it. iris-contrib/middleware/jwt/_example
cors HTTP Access Control. iris-contrib/middleware/cors/_example
secure Middleware that implements a few quick security wins. iris-contrib/middleware/secure/_example
tollbooth Generic middleware to rate-limit HTTP requests. iris-contrib/middleware/tollbooth/_examples/limit-handler
cloudwatch AWS cloudwatch metrics middleware. iris-contrib/middleware/cloudwatch/_example
new relic Official New Relic Go Agent. iris-contrib/middleware/newrelic/_example
prometheus Easily create metrics endpoint for the prometheus instrumentation tool iris-contrib/middleware/prometheus/_example
casbin An authorization library that supports access control models like ACL, RBAC, ABAC iris-contrib/middleware/casbin/_examples

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