Express middleware

In Express middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. The next middleware function is commonly denoted by a variable named next. How this middleware plays with Feathers services is outlined below.

Rendering views

While services primarily provide APIs for a client side application to use, they also play well with rendering views on the server with Express. For more details, please refer to the Using a View Engine guide.

Custom service middleware

Custom Express middleware that only should run before or after a specific service can be passed to app.use in the order it should run:

const todoService = {
  get(id) {
    return Promise.resolve({
      id,
      description: `You have to do ${id}!`
    });
  }
};

app.use('/todos', ensureAuthenticated, logRequest, todoService, updateData);

Middleware that runs after the service will have res.data available which is the data returned by the service. For example updateData could look like this:

function updateData(req, res, next) {
  res.data.updateData = true;
  next();
}

Keep in mind that shared authentication (between REST and websockets) should use a service based approach as described in the authentication guide.

Information about how to use a custom formatter (e.g. to send something other than JSON) can be found in the REST provider chapter.

Setting service parameters

All middleware registered after the REST provider has been configured will have access to the req.feathers object to set properties on the service method params:

app.configure(rest())
  .use(bodyParser.json())
  .use(bodyParser.urlencoded({extended: true}))
  .use(function(req, res, next) {
    req.feathers.fromMiddleware = 'Hello world';
    next();
  });

app.use('/todos', {
  get(id, params) {
    console.log(params.provider); // -> 'rest'
    console.log(params.fromMiddleware); // -> 'Hello world'

    return Promise.resolve({
      id, params,
      description: `You have to do ${id}!`
    });
  }
});

We recommend not setting req.feathers = something directly since it may already contain information that other Feathers plugins rely on. Adding individual properties or using Object.assign(req.feathers, something) is the more reliable option.

ProTip: Although it may be convenient to set req.feathers.req = req; to have access to the request object in the service, we recommend keeping your services as provider independent as possible. There usually is a way to pre-process your data in a middleware so that the service does not need to know about the HTTP request or response.