Interceptors

Interceptors are middleware functions that are configured to run before or after an action. They can be used for logging, authorization, etc...

Kikwit supports defining interceptors using decorators on the controller or action levels. Controller interceptors apply to all controller actions. Action interceptors apply to the decorated action only.

Interceptors have the same signature as controller actions, they accept a single Context argument.

Before interceptors

Before interceptors are specified using the @before(...interceptors) decorator.

'use strict';
import { before, controller, get } from 'kikwit';
@before(authenticate) 
@controller
export class Home {
    @get
    index(context) {
        context.sendJSON(context.locals);     
    }
    @before(authorize) 
    @get
    details(context) {
        context.sendJSON(context.locals);
    }
    @before(authorize) 
    @get
    info(context) {
        context.sendJSON(context.locals);
    }  
    @before(greet, authorize)
    @get
    hello(context) {
        context.sendJSON(context.locals);
    }
}
function authenticate(context) {
    context.locals.userId = Math.trunc(Math.random() * 1000000);     
    context.next();
}  
function authorize(context) {
    context.locals.authorized = (context.locals.userId % 2 == 0);   
    if (!context.locals.authorized) {
        return context.sendStatus(403, JSON.stringify(context.locals));
    }
    context.next();
}
function greet(context) {
    context.locals.greeted = true;   
    return context.skipToAction();
}

After interceptors

After interceptors are specified using the @after(...interceptors) decorator.

import { after, get, inject } from 'kikwit';
@after(addRandomHeader)
export class Products {
    @inject('myService')
    @get
    list(context) {      
        context.services.myService.getProducts().then(products => {
           // HTTP response will contain an 'X-RANDOM-NUMBER' header 
           context.sendJSON(products); 
        });
    }    
    @get
    hello(context) {
        // HTTP response will contain an 'X-RANDOM-NUMBER' header 
        context.send('Hello'); 
    }
}

function addRandomHeader(context) {  
    context.setHeader('X-RANDOM-NUMBER', Math.random().toString());       
    context.next();
}

Connect/Express middleware support

Connect/Express middlewares are supported via the use helper function. The use function transforms a middleware to a before interceptor.

import { before, controller, get, use } from 'kikwit';
@before(use(requestStamp))
@controller
export class Products {
    @get
    list(context) { 
        // context.request.stamp is set
        context.send('List');
    }  
    @get
    details(context) {      
        // context.request.stamp is set
        context.send('Details');
    }    
}
function requestStamp(req, res, next) { 
    req.stamp = Date.now();
    next();
};

Please always use the Context helper methods when possible and avoid accessing the underlying request and response objects directly.