# Middlewares

Middleware functions are functions that have access to the current request and can make changes that will be passed to the next request-response cycle.

Note: All express middlewares works on xpresser.

# Defining a middleware.

To create a middleware, use the xjs make:middleware command.

xjs make:middleware OnlyXhrRequests
 
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=>  OnlyXhrRequestsMiddleware created successfully. 
=>  located @ backend/middlewares/OnlyXhrRequestsMiddleware.js
 
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Notice the word Middleware is automatically added at the end of the specified name when creating the file for you.

This middleware will check if the request is a XmlHttpRequest, if true it will move to the next request cycle else it will return an error to the user.

/**
* OnlyXhrRequestsMiddleware
*/
module.exports = {

    /**
     * Handle Incoming request
     * @param {Xpresser.Http} http
     * @return any
     */
    allow(http) {
        
        if (!http.req.xhr) {
            return http.status(401).send({
                error: "Only XmlHttpRequest requests allowed."
            });
        }

        return http.next()   
    }

};
 
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if http.req.xhr is false an error response is returned else the request proceeds to the next request-cycle when http.next() is called.

# Using middlewares

There are two ways your middleware can be used in your application

• Router path middlewares
• Controller action middlewares

# Route path Middlewares

When declaring routes using $.router.path() you can assign a middleware that will affect all requests that has the router path prefixed in it.

For example, we want to add the OnlyXhrRequest to requests prefixed with /api

$.router.path("/api", () => {

    $.router.get('users', 'Api@users');
    $.router.get('posts', 'Api@posts');

}).controller('Api').middleware('OnlyXhrRequest');

$.router.get('/api/comments', 'Api@comments');
 
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/api/users and /api/posts will be guarded by the OnlyXhrRequest middleware.

Note: Routes prefixed /api/ outside and after the child routes function will also be guarded by the middleware. e.g /api/comments

# Controller action middlewares

Every controller has a middleware handler where you assign middlewares to actions.

const {ControllerClass} = require('xpresser');

class ApiController extends ControllerClass {

    /**
    * middleware - Set Middleware
    * @returns {Object}
    */
    static middleware(){
        return {}
    }

    users(http){
        return http.send({
            users: [
                {name: 'john', age: 21},
                {name: 'Doe', age: 19}
            ]       
        })
    }
}
module.exports = TestController;
 
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