Django JSON-RPC

A basic JSON-RPC Implementation for your Django-powered sites.

Features:

• Simple, pythonic API
• Support for Django authentication
• Supports JSON-RPC 1.0, 1.1, 1.2 and 2.0 Spec
• Proxy to test your JSON Service
• Run-time type checking
• Graphical JSON-RPC browser and web console
• Provides system.describe

The basic API:

myproj/myapp/views.py

from jsonrpc import jsonrpc_method

@jsonrpc_method('myapp.sayHello')
def whats_the_time(request, name='Lester'):
  return "Hello %s" % name

@jsonrpc_method('myapp.gimmeThat', authenticated=True)
def something_special(request, secret_data):
  return {'sauce': ['authenticated', 'sauce']}

myproj/urls.py

from django.conf.urls.defaults import *
from jsonrpc import jsonrpc_site
import myproj.myapp.views # you must import the views that need connected

urlpatterns = patterns('', 
  url(r'^json/browse/', 'jsonrpc.views.browse', name="jsonrpc_browser"), # for the graphical browser/web console only, omissible
  url(r'^json/', jsonrpc_site.dispatch, name="jsonrpc_mountpoint"),
  (r'^json/(?P<method>[a-zA-Z0-9.]+)$', jsonrpc_site.dispatch) # for HTTP GET only, also omissible
)

To test your service: You can test your service using the provided graphical browser and console, available at http://YOUR_URL/json/browse/ (if using the url patterns from above) or with the included ServiceProxy:

>>> from jsonrpc.proxy import ServiceProxy

>>> s = ServiceProxy('http://localhost:8080/json/')

>>> s.myapp.sayHello('Sam')
{u'error': None, u'id': u'jsonrpc', u'result': u'Hello Sam'}

>>> s.myapp.gimmeThat('username', 'password', 'test data')
{u'error': None, u'id': u'jsonrpc', u'result': {u'sauce': [u'authenticated', u'sauce']}}

We add the jsonrpc_version variable to the request object. It be either '1.0', '1.1' or '2.0'. Arg.

Guide

Adding JSON-RPC to your application

1. Install django-json-rpc

git clone git://github.com/samuraisam/django-json-rpc.git
cd django-json-rpc
python setup.py install

# Add 'jsonrpc' to your INSTALLED_APPS in your settings.py file

2. Write JSON-RPC methods

from jsonrpc import jsonrpc_method

@jsonrpc_method('app.register')
def register_user(request, username, password):
  u = User.objects.create_user(username, 'internal@app.net', password)
  u.save()
  return u.__dict__

@jsonrpc_method('app.change_password', authenticated=True)
def change_password(request, new_password):
  request.user.set_password(new_password)
  request.user.save()
  return u.__dict__

3. Add the JSON-RPC mountpoint and import your views

from jsonrpc import jsonrpc_site
import app.views

urlpatterns = patterns('', 
  url(r'^json/$', jsonrpc_site.dispatch, name='jsonrpc_mountpoint'),
  # ... among your other URLs
)

The jsonrpc_method decorator

Wraps a function turns it into a json-rpc method. Adds several attributes to the function speific to the JSON-RPC machinery and adds it to the default jsonrpc_site if one isn't provided. You must import the module containing these functions in your urls.py.

jsonrpc.jsonrpc_method(name, authenticated=False, safe=False, validate=False)

• `name`

  The name of your method. IE: namespace.methodName

• `authenticated=False`

  Adds username and password arguments to the beginning of your method if the user hasn't already been authenticated. These will be used to authenticate the user against django.contrib.authenticate If you use HTTP auth or other authentication middleware, username and password will not be added, and this method will only check against request.user.is_authenticated.

  You may pass a callablle to replace django.contrib.auth.authenticate as the authentication method. It must return either a User or None and take the keyword arguments username and password.

• `safe=False`

  Designates whether or not your method may be accessed by HTTP GET. By default this is turned off.

• `validate=False`

  Validates the arguments passed to your method based on type information provided in the signature. Supply type information by including types in your method declaration. Like so:

    @jsonrpc_method('myapp.specialSauce(Array, String)', validate=True)
    def special_sauce(self, ingredients, instructions):
      return SpecialSauce(ingredients, instructions)
  

  Calls to myapp.specialSauce will now check each arguments type before calling special_sauce, throwing an InvalidParamsError when it encounters a discrepancy. This can significantly reduce the amount of code required to write JSON-RPC services.

  NOTE: Type checking is only available on Python versions 2.6 or greater.

• `site=default_site`

  Defines which site the jsonrpc method will be added to. Can be any object that provides a register(name, func) method.

Using type checking on methods (Python 2.6 or greater)

When writing web services you often end up manually checking the types of parameters passed. django-json-rpc provides a way to eliminate much of that code by specifying the types in your method signature. As specified in the JSON-RPC spec the available types are Object Array Number Boolean String Nil and Any meaning any type.

  @jsonrpc_method('app.addStrings(arg1=String, arg2=String) -> String', validate=True)
  def add_strings(request, arg1, arg2):
    return arg1 + arg2

However contrived this example, a lot of extra information about our function is available. The system.describe method will automatically be able to provide more information about the parameters and return type. Provide validate=True to the jsonrpc_method decorator and you can be guaranteed to receive two string objects when add_strings is called.

Note: Return type information is used only for reference, return value types are not checked.

Types can be specified a number of ways, the following are all equivalent:

  # using JSON types:
  @jsonrpc_method('app.findSelection(query=Object, limit=Number)')
  
  # using Python types:
  @jsonrpc_method('app.findSelection(query=dict, limit=int)')
  
  # with mixed keyword parameters
  @jsonrpc_method('app.findSelection(dict, limit=int)')
  
  # with no keyword parameters
  @jsonrpc_method('app.findSelection(dict, int)')
  
  # with a return value
  @jsonrpc_method('app.findSelection(dict, int) -> list')

Using the browser

To access the browser simply add another entry to your urls.py file, before the json dispatch one. Make sure to include the name attribute of each url.

urlpatterns = patterns('',
  ...
  url(r'^json/browse/$', 'jsonrpc.views.browse', name='jsonrpc_browser')
  url(r'^json/', jsonrpc_site.dispatch, name="jsonrpc_mountpoint"),
  ...
)

Enabling HTTP-GET

JSON-RPC 1.1 includes support for methods which are accessible by HTTP GET which it calls idempotent. Add the following to your urls.py file to set up the GET URL.

urlpatterns += patterns('', 
  (r'^json/(?P<method>[a-zA-Z0-9.-_]+)$', jsonrpc_site.dispatch),
)

Each method that you want to be accessible by HTTP GET must also be marked safe in the method decorator:

@jsonrpc_method('app.trimTails(String)', safe=True)
def trim_tails(request, arg1):
  return arg1[:5]

You can then call the method by loading /jsonrpc/app.trimTails?arg1=omgnowai

Using authentication on methods

There is no specific support for authentication in the JSON-RPC spec beyond whatever authentication the transport offers. To restrict access to methods to registered users provide authenticated=True to the method decorator. Doing so will add two arguments to the beginning of your method signature, username and password (and always in that order). By default, the credentials are authenticated against the builtin User database but any method can be used.

@jsonrpc_method('app.thupertheecrit', authenticated=True)
def thupertheecrit(request, value):
  p = request.user.get_profile()
  p.theecrit = value
  p.save()
  return p.__dict__

Using your own authentication method:

def mah_authenticate(username, password):
  return CustomUserClass.authenticate(username, password)

@jsonrpc_method('app.thupertheecrit', authenticated=mah_authenticate)
def thupertheecrit(request, value):
  request.user.theecrit = value
  request.user.save()
  return request.user.__dict__

In case authentication is handled before your method is called, like in some middleware, providing authenticated=True to the method decorator will only check that request.user is authenticated and won't add any parameters to the beginning of your method.