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Damn simple, framework-agnostic JSON-RPC server

Project description

JSON-RPC Server for Python

This is damn simple, framework-agnostic JSON-RPC v2.0 server for Python.

This package has no dependencies. You can build service API without thinking about any framework nor toolkit, and even without thinking about HTTP itself. This package is an implementation of JSON-RPC protocol only, following rules described on http://www.jsonrpc.org/specification

What is JSON-RPC?

JSON-RPC is a protocor similar to XML-RPC, but simpler and very lightweight. There is no necessary to generate nor parse XML documents by using heavy librariers.

You can build easily remote services and call them using clients implemented in many languages. JSON-RPC services are always exposed using HTTP(S) protocol.

For more information please read JSON-RPC v2.0 specification: http://www.jsonrpc.org/specification

Getting started

Installation

Use setuptools or pip:

easy_install damn-simple-jsonrpc-server

or

pip install damn-simple-jsonrpc-server

Calculator service example

Let's make calculator service which supports add and subtract operations.

(calculator_service.py)

import jsonrpcserver as rpc

calculator = rpc.Service()

@calculator.method
def add(x, y):
    return x+y

@calculator.method('subtract')
def sub(x, y):
    return x-y

Well... it's done. But where it is accessible? Nowhere! You can access it directly by calculator variable, but this is nonsense. This is an API for HTTP adapters, but not for humans.

Exposing JSON-RPC service via HTTP

Simplest way to expose calculator service is to use well-known HTTP framework. It may be a Django, for example:

(urls.py)

from django.conf.urls import patterns, include, url
from .calculator_service import calculator

def calculator_service_view(request):
    return calculator.handle_request_body(request.body)

urlpatterns = patterns('',
        url(r'^$', calculator_service_view, name='calculator'),
)

But there is a simpler way! :)

Using existing adaptors

If you need quickly expose your service using Django, just use damn simple JSON-RPC Django adaptor, which contains ready to use adaptor:

(urls.py)

from django.conf.urls import patterns, include, url
from calculator_service import calculator

urlpatterns = patterns('',
        url(r'^$', 'jsonrpcdjango.serve', kwargs={'service': calculator},
            name='calculator'),
)

That's all. Nothing more, nothing less!

Writing custom adaptors

JSON-RPC Service class has very simple API based on str/unicode or request-like object. You may use one of the following methods available in Service class:

  • handle_request_body
  • handle_http_request

The handle_request_body method expects that input string will be a representation of a JSON-RPC Request object.

The handle_http_request method expects that request-like object will be passed as an argument. In that case request-like object must contain body attribute with string representation of JSON-RPC request.

Return value of handle_request_body and handle_http_request is always a str/unicode with a JSON-RPC Response object representation (success and error responses are returned same way, as described in http://www.jsonrpc.org/specification, but will contain result and error keys respectively).

Authentication, CSRF, other stuff...

Authentication and CSRF are HTTP-related topics. You may implement them in adaptors or just use tools from your favourite HTTP framework. For Django framework you may simply decorate whole service:

(urls.py)

import jsonrpcdjango as rpc

[...]

urlpatterns = patterns('',
        url(r'^$', login_required(rpc.serve), kwargs={'service': calculator},
            name='calculator'),

To enable or disable CSRF just use specific adaptor:

  • jsonrpcdjango.serve for CSRF-less handler
  • jsonrpcdjango.csrf_serve for CSRF-protected handler
  • or use disrectly Django's decorators csrf_exempt, csrf_protect or enable CsrfViewMiddleware (read https://docs.djangoproject.com/en/dev/ref/csrf/ for details)

Currently there is no possibility to decorate specific methods of the service with jsonrpcdjango adaptor.

Authorization

If you want add authorization to your method you should use similar solution as for authentication. For Django framework you may simply decorate whole service:

(urls.py)

import jsonrpcdjango as rpc

[...]

urlpatterns = patterns('',
        url(r'^$', permission_required('can_use_rpc')(rpc.serve), kwargs={'service': calculator},
            name='calculator'),

Currently there is no possibility to decorate specific methods of the service with jsonrpcdjango adaptor.

Accessing original HTTP request inside service methods

Sometimes you may need access to specific request data added somewhere in middleware stack. In that case you can register JSON-RPC method with additional argument takes_http_request=True. Original request object will be passed as first argument.

If you're using Django as an HTTP framework and jsonrpcdjango adaptor, you can provide access to Django's HttpRequest object inside service method without any hacks. Just declare takes_http_request=True at registering time. This will make your service dependend on Django, but will add more flexibility.

(calculator_service.py)

calculator = rpc.Service()

[...]

@calculator.method(takes_http_request=True)
def beast_add(request, x, y):
    if request.user.is_superuser:
        return x+y
    else:
        return 666

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