How to Implement Middleware Pipeline in VueJS.pdf

How to
Implement
Middleware
Pipeline in
VueJS?
www.bacancytechnology.com

A middleware is one of the most commonly
used terms in web development that act as
an intermediate between two applications
or services. The powerful concept of
middleware helps developers with routing
and patterns related to it.

In VueJS, middleware can be used for
multiple layout switching, restricting some
routes as per the user role, etc. This tutorial
will discuss the steps to implement
middleware pipeline in VueJS and further
learn how you can use multiple
middlewares on single routes.

Let me list out some prerequisites for you.

Prerequisites
: Implement
Middleware
Pipeline in
VueJS

1. Basic knowledge about the working of
VueJS
2. Familiarity with vue-router and
navigation guards in Vue.js,

And that’s it; we are good to go now
Create VueJS App
With the help of the vue-cli
tool, create a VueJS project.
Vue create vue-middleware-demo

You will be prompted to choose the Vue
version, select vue-2
After selecting the relevant version, vue-
cli will install the dependencies, and now
we can serve our project.
We have successfully created a new
project,

Install vue-router
Install vue-router using the below
command. Here we will be using yarn to
install vue-router; you can choose as per
your convenience.
If you are not familiar with vue-router, you
can visit the Getting Started with Vue
Router blog to explore more about it.
cd vue-middleware-demo
yarn add vue-router
Use the below command to serve the
project.
yarn run serve

The initial default user interface will look
something like this. Moving further in the
tutorial, we will configure the routers in the
next section.
Creating Routes
In this section, we will set up some basic
routes. Our demo application will have two
web pages for Login and User’s profile.
The structure will look like this.

../vue-middleware-
demo/src/pages/Login.vue
../vue-middleware-
demo/src/pages/UserProfile.vue
Create router.js file within src directory to
configure routes for the demo application.
// router.js
import Vue from "vue";
import VueRouter from "vue-router";

import LoginPage from
"@/pages/LoginPage.vue"
import UserProfile from
"@/pages/UserProfile.vue"
import HelloWorld from
"./components/HelloWorld"

Vue.use(VueRouter)

const appRoutes = [
{
path: '/',
name: 'home',
component: HelloWorld
},
{
path: '/login',
name: 'login',
component: LoginPage
},
{
path: '/user-profile',
name: 'user.profile',
component: UserProfile
}
]
const routes = [...appRoutes]

const router = new VueRouter({

mode: 'history',
routes
})
export default router
We are almost done with the configuration.
Now, add router-view in App.vue to make
them accessible.
// App.vue
<template> <div id="app">
<img alt="Vue logo"
src="./assets/logo.png"> <router-
view></router-view> 
</div> </template>
<script> export default { name:
'App', } </script>

UI for /login and UI for /user-profileRoute
Creating Middlewares
Create our first middleware guest.js which
will be responsible for navigating to the
user-profile page only if the user is logged
in.

// guest.js
export default function guest({next,store}){
let isLoggedIn = false // Can be calculated
through store
if(isLoggedIn){
return next({
name: 'home'
})
}

return next();
}
Now we need to create a middleware
pipeline. The pipeline is responsible for
communication between navigation guards
and middlewares. Simply create a file named
middleware-pipeline.js and use the below
code snippet.

function middlewarePipeline (context,
middleware, index) {
const nextMiddleware =
middleware[index]

if(!nextMiddleware){
return context.next
}

return () => {
const nextPipeline =
middlewarePipeline(
context, middleware, index + 1
)

nextMiddleware({ ...context, next:
nextPipeline })

}
}
export default middlewarePipeline

Once you are done with this file, configure
it in router.js. We’ll use navigation guard
and middleware-pipeline to execute
middleware.
// router.js
router.beforeEach((to, from, next) => {

/** Navigate to next if middleware is not
applied */
if (!to.meta.middleware) {
return next()
}

const middleware = to.meta.middleware;
const context = {
to,
from,
Next,
// store | You can also pass store as an
argument
}

return middleware[0]({
...context,
next:middlewarePipeline(context, middleware,1
})
})
The connection is established now.
The next step is to configure the
middleware in the required path, for now
we will implement guest middleware in
/login which means if the user is logged in
(hard coded for now) then it redirects the
user from Login page to Home page.
So let’s add this middleware to our routes.
Use the following object where you want to
apply the middleware.

Remember: You need to import guest
middleware then only you will be able to
configure it

{
path: '/login',
name: 'login',
meta: {
middleware: [
guest
]
},
},
After all these changes to router.js this is
how your file should look like

import guest from "./middleware/guest" //
Change: Import Middleware
import middlewarePipeline from
"./middleware/middleware-pipeline";

Vue.use(VueRouter)

const appRoutes = [
{
path: '/',
name: 'home',
},
{
path: '/login',
name: 'login',
meta: {
middleware: [
guest

},
},
{
}
]

mode: 'history',
routes
})

applied */
return next()

const context = {
to,
from,
next,
argument
}

...context,
next:middlewarePipeline(context,
middleware,1)
})
})

Navigate to http://localhost:8080/login you
will notice that you are being redirected to
Home Page or http://localhost:8080/ route.
Congratulations! You have successfully
implemented a middleware pipeline in
Vue.js.
Now, it’s time to add multiple middlewares
to the same routes.
Configure Multiple
Middlewares
Hoping that you remember that we have
added some extra metadata to the Login
route. This is how the path object should
look like.

{
path: '/login',
name: 'login',
meta: {
middleware: [
guest
]
},
},
Notice the middleware key here. A
middleware key is a type of array which
means that we can pass multiple
middleware to this key.
So, let’s create one more middleware with
the name auth.js which we will use for user
authenticated pages. For example, we will
apply this middleware to /user-profile page
and this page is only accessible to logged-in
users. If the user is not logged in then this
middleware will push the user to the login
page.

// auth.js
export default function auth({next,store}){
let isLoggedIn = false // Can be
calculated through store
// let isLoggedIn =
store.getters['sessionData/isLoggedIn']
if(!isLoggedIn){
return next({
name:'login'
})
}

return next()
}

Now in router.js you can configure multiple
middleware as shown below.

// router.js

import auth from "./middleware/auth";
import middlewarePipeline from
"./middleware/middleware-pipeline";
import guest from "./middleware/guest";

Vue.use(VueRouter)

const appRoutes = [
{

path: '/',
name: 'home',
},
{
path: '/login',
name: 'login',
},
{
meta: {
middleware: [
auth, guest
]
},
}
]


mode: 'history',
routes
})


applied */
return next()
}

const context = {
to,
from,
next,

}
...context,
next:middlewarePipeline(context,
middleware,1)
})
})

Note: Here auth and guest both these
middleware are contradictory to each other
so in this example we will see how we can
configure multiple middleware.

You can utilize this middleware to fetch
relevant data. For example, you can fetch
auth related data in auth middleware and
can ignore guest users. It’s all up to you how
you want to use it.

So, that’s it we are done implementing the
middleware pipeline in VueJS!

Github
Repository:
Middleware
Pipeline
Example

Feel free to visit the source code and clone
the repository using the below command.
git clone
https://github.com/iamsantoshyadav/vue-
middleware-demo.git

Conclusion
That’s it for the tutorial on how to
implement a middleware pipeline in VueJS.
Middlewares are an excellent way to protect
various routes of your application. This was
just a simple demonstration of how you can
get started with middleware in VueJS.
Please write to us back with any
suggestions or feedback. You can also visit
Vuejs tutorials page where you can find
similar topics with the GitHub repository to
play around with the code.

Thank You
www.bacancytechnology.com

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