QVC

for node.js

This is an implementation of the QVC protocol for node. It supports commands and queries, and simple constraints, but not validation (yet).

Installation

Install it from npm using npm install qvc. This will install all needed dependencies

About QVC

QVC is an alternative to REST which adds validation and error handling to ajax requests. It is a protocol on top of the HTTP layer using JSON to encode data in both directions. QVC is short for Query Validation Command, describing the three parts of the protocol. A request to the server can either be a query, where the server should return a result, or a command, where the server should do some action. In both cases the client can send parameters to the server in the form of a JSON object. This JSON object is validated on the server, and the result of the validation is sent to the client in a standardized format. The protocol also provides a way to send validation constraints to the client, for client-side validation of parameters.

Usage

There are two parts to using QVC; creating a command/query handler and routing to it. The command/query handler is a function which takes a command/query as its first parameter, and calls the second parameter with the result (standard node.js callback style). For example:

var qvc = require('qvc');
 
module.exports = [
  qvc.query('load', function(query, done){
    console.log("load", query.name);
 
    loadDataAsync(function(err, result){
      //transform the result somehow
      done(err, result);
    });
  }),
  qvc.command('save', function(command, done){
    console.log("save", command.name);
    
    saveDataAsync(command.name, command.content, function(err, success){
      done(err, success);
    });
  })
];

This file contains both a command and a query handler, and can be expanded in the future with additional commands and queries. A project can consist of several files like this, with multiple handlers for both commands and queries.

A single routing file is needed for all this to work. An example is presented here:

var qvc = require('qvc');
var express = require('express');
var bodyParser = require('body-parser');
 
var app = express();
 
app.use(bodyParser.urlencoded());
 
app.use('/qvc', qvc(
  require('./handlers'),
  //add other handlers here...
));
 
app.listen(80);