Rewrite Middleware

When the Application's requirements suggests that the redirect rules should be registered in one place then use the Rewrite Middleware. The Rewrite Middleware supports rewrite URL path, subdomain or host based on a regular expression search and replace.

The syntax is familiar to the majority of the backend developers out there and it looks like that:

REDIRECT_CODE_DIGITS	PATTERN_REGEX	TARGET_REPL
301	/seo/(.*)	/$1

The above will redirect all requests from relative path /seo/* to /* using the 301 (Moved Permanently) HTTP Status Code. Learn more about regex.

Usage

First of all, you should import the builtin middleware as follows:

import "github.com/kataras/iris/v12/middleware/rewrite"

There are two ways to load rewrite options in order to parse and register the redirect rules:

1. Through a yaml or json file using the Load function. It is the most common scenario and the simplest one. It panics on parse errors.

func main() {
    app := iris.New()
    // [...routes]
    redirects := rewrite.Load("redirects.yml")
    app.WrapRouter(redirects)
    app.Listen(":80")
}

It is highly recommended that you should register the Rewrite Middleware as a Router Wrapper through Application.WrapRouter right before Application.Listen/Run.

The "redirects.yml" file looks like that:

RedirectMatch:
  # Redirects /seo/* to /*
  - 301 /seo/(.*) /$1

  # Redirects /docs/v12* to /docs
  - 301 /docs/v12(.*) /docs

  # Redirects /old(.*) to /
  - 301 /old(.*) /

  # Redirects http or https://test.* to http or https://newtest.*
  - 301 ^(http|https)://test.(.*) $1://newtest.$2

  # Handles /*.json or .xml as *?format=json or xml,
  # without redirect. See /users route.
  # When Code is 0 then it does not redirect the request,
  # instead it changes the request URL
  # and leaves a route handle the request.
  - 0 /(.*).(json|xml) /$1?format=$2

# Redirects root domain to www.
# Creation of a www subdomain inside the Application is unnecessary,
# all requests are handled by the root Application itself.
PrimarySubdomain: www

2. Through code using the New function. Parse errors can be handled and rules can be programmatically stored.

opts := rewrite.Options{
	RedirectMatch: []string{
		"301 /seo/(.*) /$1",
		"301 /docs/v12(.*) /docs",
		"301 /old(.*) /",
		"301 ^(http|https)://test.(.*) $1://newtest.$2",
		"0 /(.*).(json|xml) /$1?format=$2",
	},
	PrimarySubdomain: "www",
}
rw, err := rewrite.New(opts)
if err != nil { panic(err) }
app.WrapRouter(rw.Rewrite)

Example

Let's write a simple application which follows the redirect rules of:

SOURCE	TARGET
http://mydomain.com:8080/seo/about	http://www.mydomain.com:8080/about
http://test.mydomain.com:8080	http://newtest.mydomain.com:8080
http://test.mydomain.com:8080/seo/about	http://newtest.mydomain.com:8080/about
http://mydomain.com:8080/seo	http://www.mydomain.com:8080
http://mydomain.com:8080/about	http://www.mydomain.com:8080/about
http://mydomain.com:8080/docs/v12/hello	http://www.mydomain.com:8080/docs
http://mydomain.com:8080/docs/v12some	http://www.mydomain.com:8080/docs
http://mydomain.com:8080/oldsome	http://www.mydomain.com:8080
http://mydomain.com:8080/oldindex/random	http://www.mydomain.com:8080
http://mydomain.com:8080/users.json	http://www.mydomain.com:8080/users?format=json

package main

import (
	"github.com/kataras/iris/v12"
	"github.com/kataras/iris/v12/middleware/rewrite"
)

func main() {
	app := iris.New()

	app.Get("/", index)
	app.Get("/about", about)
	app.Get("/docs", docs)
	app.Get("/users", listUsers)

	app.Subdomain("test").Get("/", testIndex)

	newtest := app.Subdomain("newtest")
	newtest.Get("/", newTestIndex)
	newtest.Get("/", newTestAbout)

    //
	redirects := rewrite.Load("redirects.yml")
    app.WrapRouter(redirects)
    // 

	app.Listen(":8080")
}

func index(ctx iris.Context) {
	ctx.WriteString("Index")
}

func about(ctx iris.Context) {
	ctx.WriteString("About")
}

func docs(ctx iris.Context) {
	ctx.WriteString("Docs")
}

func listUsers(ctx iris.Context) {
	format := ctx.URLParamDefault("format", "text")
	/*
		switch format{
			case "json":
				ctx.JSON(response)
			case "xml":
				ctx.XML(response)
			// [...]
		}
	*/
	ctx.Writef("Format: %s", format)
}

func testIndex(ctx iris.Context) {
    ctx.WriteString(`Test Subdomain Index
				(This should never be executed,
				redirects to newtest subdomain)`)
}

func newTestIndex(ctx iris.Context) {
	ctx.WriteString("New Test Subdomain Index")
}

func newTestAbout(ctx iris.Context) {
	ctx.WriteString("New Test Subdomain About")
}

Hosts File

127.0.0.1	mydomain.com
127.0.0.1	www.mydomain.com
127.0.0.1	test.mydomain.com
127.0.0.1	newtest.mydomain.com

Navigate here if you don't know how to modify the system's hosts file.