Skip to main content

ColdFusion 10: HTTP Content Negotiation + REST– Part 2

Following with my previous post on how content negotiation between the client and server help in invoking an appropriate REST service. In this post I’ll explain how one can specify multiple mime types in the request header and also the quality factor that enables server to decide which mime type to serve for the incoming request. The client sends a HTTP request to the Server along with several headers, one of them is the Accept header. The Accept header can contain a list of mime types that the client (user agent) is willing to process. These mime types are separated by a comma and may optionally be combined with the quality factor.

A CFC can contain several methods with produces attribute set to a specific mime type. The Accept header may contain several mime types:

text/html, text/plain, application/xml, application/json, */*

Server would parse the Accept header and will search for a REST service that matches the mime type specified first in the Accept header list. In this case ‘text/html’, if the same is not found then the next one in the list – text/plain. The client would specify the order of preference in the Accept header.

The Accept header can also specify the quality factory along with the mime types which defines relative degree of preference between different mime types. Here the header will be of the form:

text/html;q=0.7, text/plain;q=0.8, application/xml;q=0.9

Here the preference for each of the mime types is specified as quality factor in the header. The method with produces attribute set to ‘application/xml’ would be invoked because its quality factor – 0.9 is higher than the other mime types. By default the quality factory is 1 and it can have values between 0 and 1.

A REST request can also be sent through a browser by providing the URI in the address bar. Here the browser would send the default Accept header and an appropriate REST service would be invoked. Therefore if you try to send the same request from two different browsers, it would return different results.
Labels:

Comments

Post a Comment

Popular posts from this blog

File upload and Progress events with HTML5 XmlHttpRequest Level 2

The XmlHttpRequest Level 2 specification adds several enhancements to the XmlHttpRequest object. Last week I had blogged about cross-origin-requests and how it is different from Flash\Silverlight's approach .  With Level 2 specification one can upload the file to the server by passing the file object to the send method. In this post I'll try to explore uploading file using XmlHttpRequest 2 in conjunction with the progress events. I'll also provide a description on the new HTML5 tag -  progress which can be updated while the file is being uploaded to the server. And of course, some ColdFusion code that will show how the file is accepted and stored on the server directory.
18 comments
Read more

How to use the APP_INITIALIZER token to hook into the Angular bootstrap process

I've been building applications using Angular as a framework of choice for more than a year and this post is not about another React vs Angular or the quirks of each framework. Honestly, I like Angular and every day I discover something new which makes development easier and makes me look like a guy who built something very complex in a matter of hours which would've taken a long time to put the correct architecture in place if I had chosen a different framework. The first thing that I learned in Angular is the use of the APP_INITIALIZER token.
Post a Comment
Read more

On GraphQL and building an application using React Apollo

When I visualize building an application, I would think of using React and Redux on the front-end which talks to a set of RESTful services built with Node and Hapi (or Express). However, over a period of time, I've realized that this approach does not scale well when you add new features to the front-end. For example, consider a page that displays user information along with courses that a user has enrolled in. At a later point, you decide to add a section that displays popular book titles that one can view and purchase. If every entity is considered as a microservice then to get data from three different microservices would require three http  requests to be sent by the front-end app. The performance of the app would degrade with the increase in the number of http requests. I read about GraphQL and knew that it is an ideal way of building an app and I need not look forward to anything else. The GraphQL layer can be viewed as a facade which sits on top of your RESTful services o...
Post a Comment
Read more