sprockets.mixins.mediatype

A mixin that performs Content-Type negotiation and request/response (de)serialization.

This mix-in adds two methods to a tornado.web.RequestHandler instance:

• get_request_body() -> dict: deserializes the request body according to the HTTP Content-Type header and returns the deserialized body.

• send_response(object): serializes the response into the content type requested by the Accept header.

Before adding support for specific content types, you SHOULD install the content settings into your tornado.web.Application instance. If you don’t install the content settings, then an instance will be created for you by the mix-in; however, the created instance will be empty. You should already have a function that creates the Application instance. If you don’t, now is a good time to add one.

from sprockets.mixins.mediatype import content
from tornado import web

def make_application():
    application = web.Application([
        # insert your handlers here
    ])
    content.install(application, 'application/json', 'utf-8')
    return application

Support for a content types is enabled by calling add_binary_content_type, add_text_content_type or the add_transcoder functions with the tornado.web.Application instance, the content type, encoding and decoding functions as parameters:

import json

from sprockets.mixins.mediatype import content
from tornado import web

def make_application():
    application = web.Application([
        # insert your handlers here
    ])

    content.install(application, 'application/json', 'utf-8')
    content.add_text_content_type(application,
                                  'application/json', 'utf-8',
                                  json.dumps, json.loads)

    return application

The add content type functions will add a attribute to the Application instance that the mix-in uses to manipulate the request and response bodies. The add_transcoder function is similar except that it takes an object that implements transcoding methods instead of simple functions. The transcoders module includes ready-to-use transcoders for a few content types:

from sprockets.mixins.mediatype import content, transcoders
from tornado import web

def make_application():
    application = web.Application([
        # insert your handlers here
    ])

    content.install(application, 'application/json', 'utf-8')
    content.add_transcoder(application, transcoders.JSONTranscoder())

    return application

In either case, the ContentMixin uses the registered content type information to provide transparent content type negotiation for your request handlers.

from sprockets.mixins.mediatype import content
from tornado import web

class SomeHandler(content.ContentMixin, web.RequestHandler):
    def get(self):
        self.send_response({'data': 'value'})

    def post(self):
        body = self.get_request_body()
        # do whatever
        self.send_response({'action': 'performed'})

Based on the settings stored in the Application instance and the HTTP headers, the request and response data will be handled correctly or the appropriate HTTP exceptions will be raised.