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CRUD operations on persistent connection stores #node.js #javascript
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CRUDr

Open source module for socket-enabled CRUD operations in Node.js

Features

  • Authentication compatible with OAuth2 (using middleware)
  • Session support

Install

    npm install crudr

Dependencies

  • Socket.io
  • Express (only for uri routes)
  • Underscore

Usage

On the server:

    var http = require('http'),
    crudr = require('crudr'),
    app = http.createServer(),

    app.listen(80);
    crudr.listen(options);

On the client:

    <script src="/crudr.js"></script>

    <script>
        crudr.connect( options, function(){
            // .. initiate app
        });
    </script>

Authority

Part of the main options of the lib is passing a custom method under the authority key. This method will be triggered every time a token needs to be verified. It is assumed that it will be part of your app and connected to the necessary modules that will make this verification possible.

An example of the basic scaffolding follows:

function( req, res, callback ){

    var token = req.data;
    // db already available...
    db.find({ token: token }, function( data ){
        callback( data );
    });

}

Note: A token is required when authentication is activated, so make sure you obtain one from your backend before running crudr.connect

Events

When a model is synced with a particular backend, the backend will trigger events on the object (across multiple clients) that share the backend.

To initialize the binding logic we create a backend key on the object of specific Model we are interested in

For example,

var Model;
...
Model.backend = "{{name}}";
Model.backend = buildBackend( Model );

We can keep data synced in realtime with the following event bindings:

    var self = this;

    element.addEventListener('{{name}}:create', function(e) {
        var data = e.response;
    }, false);
    element.addEventListener('{{name}}:update', function(e) {
        var data = e.response;
    }, false);
    element.addEventListener('{{name}}:delete', function(e) {
        var data = e.response;
    }, false);

In addition to {{name}}:create, {{name}}:read, {{name}}:update, and {{name}}:delete events, a generic {{name}} event is also triggered when a model is synced.

    element.addEventListener('{{name}}', function(e) {
        // Method will be one of create, read, update, or delete
        var method = e.method;
        var data = e.response;
    });

The event prefix backend is used by default but this can be customized by setting the event name on the server.

    options.event = '{{name}}';
    crudr.listen(options);

More information on the initialization options is available at the wiki

Backends

Backends are stacks of composable middleware (inspired by Connect) that are responsible for handling sync requests and responding appropriately. Each middleware is a function that accepts request and response objects (and optionally a function that can be called to continue down the stack). A middleware will generally either return a result by calling end on the response object or pass control downward. For example, to add a logger to our backend:

var backend = crudr.createBackend();
backend.use(function(req, res, next) {
    console.log(req.backend);
    console.log(req.method);
    console.log(JSON.stringify(req.model));
    next();
});

backend.use(crudr.helpers.memoryStore());

A request object will contain the following objects (in addition to those set by the various middleware):

  • method: the sync method (create, read, update, or delete)
  • model: the model object to by synced
  • options: any options set by the client (except success and error callbacks)
  • backend: name of the backend responsible for handling the request
  • socket: the client socket that initiated the request

We can also target only particular types of requests by passing the desired contexts to use:

backend.use('create', 'update', 'delete', function(req, res, next) {
    if (isAuthorized(req)) {
        next();
    } else {
        next(new Error('Unauthorized'));
    }
});

Or alternatively by using one of the four helper methods (create, read, update, delete):

backend.read(function(req, res) {
    if (req.model.id) {
        req.end(mymodels[req.model.id]);
    } else {
        req.end(mymodels);
    }
});

If the bottom of the middleware stack is reached before a result is returned then the requested model is returned by default: res.end(req.model).

Clients are automatically notified of events triggered by other clients, however, there may be cases where other server-side code needs to make updates to a model outside of a backend handler. In such a case, one can notify clients by emitting events directly on the backend. For example:

var backend = crudr.createBackend();
backend.use(crudr.helpers.memoryStore());

// Clients will receive 'backend:create', 'backend:update',
// and 'backend:delete' events respectively.
backend.emit('created', { id: 'myid', foo: 'bar' });
backend.emit('updated', { id: 'myid', foo: 'baz' });
backend.emit('deleted', { id: 'myid' });

Sessions

Sessions are supported as an extension of the initialization options. Fore example:

var session = require('express-session');
var RedisStore = require('connect-redis')(session);

var options = {
    ...
    session: {
        store: new RedisStore(options),
        secret: 'keyboard cat'
    }
};

// initialize CRUDr
crudr.listen(options);

The session attribute is an sub-object of related options. Essential attributes are the store and secret used for the sessions. Extended attributes include the optional parser (defaults to a new instance of the cookieParser) and key (defaults to 'sid')

Customizing

In addition to middleware, the behavior of CRUDr can be customized via standard Socket.IO mechanisms. The object returned from the call to listen is the Socket.IO object and can be manipulated further. See http://socket.io for more details.

Tests

Install development dependencies:

npm install

Run the test suite:

make test

Constributors

Credits

Distributed by Makesites.org

Released under the Apache License, Version 2.0

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