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# A reaction to: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/552751
from webob import Request, Response
from webob import exc
from simplejson import loads, dumps
import traceback
import sys
class JsonRpcApp(object):
"""
Serve the given object via json-rpc (http://json-rpc.org/)
"""
def __init__(self, obj):
self.obj = obj
def __call__(self, environ, start_response):
req = Request(environ)
try:
resp = self.process(req)
except ValueError, e:
resp = exc.HTTPBadRequest(str(e))
except exc.HTTPException, e:
resp = e
return resp(environ, start_response)
def process(self, req):
if not req.method == "POST":
raise exc.HTTPMethodNotAllowed("Only POST allowed", allowed="POST")
try:
json = loads(req.body)
except ValueError, e:
raise ValueError("Bad JSON: %s" % e)
try:
method = json["method"]
params = json["params"]
id = json["id"]
except KeyError, e:
raise ValueError("JSON body missing parameter: %s" % e)
if method.startswith("_"):
raise exc.HTTPForbidden(
"Bad method name %s: must not start with _" % method
)
if not isinstance(params, list):
raise ValueError("Bad params %r: must be a list" % params)
try:
method = getattr(self.obj, method)
except AttributeError:
raise ValueError("No such method %s" % method)
try:
result = method(*params)
except:
text = traceback.format_exc()
exc_value = sys.exc_info()[1]
error_value = dict(
name="JSONRPCError", code=100, message=str(exc_value), error=text
)
return Response(
status=500,
content_type="application/json",
body=dumps(dict(result=None, error=error_value, id=id)),
)
return Response(
content_type="application/json",
body=dumps(dict(result=result, error=None, id=id)),
)
class ServerProxy(object):
"""
JSON proxy to a remote service.
"""
def __init__(self, url, proxy=None):
self._url = url
if proxy is None:
from wsgiproxy.exactproxy import proxy_exact_request
proxy = proxy_exact_request
self.proxy = proxy
def __getattr__(self, name):
if name.startswith("_"):
raise AttributeError(name)
return _Method(self, name)
def __repr__(self):
return "<%s for %s>" % (self.__class__.__name__, self._url)
class _Method(object):
def __init__(self, parent, name):
self.parent = parent
self.name = name
def __call__(self, *args):
json = dict(method=self.name, id=None, params=list(args))
req = Request.blank(self.parent._url)
req.method = "POST"
req.content_type = "application/json"
req.body = dumps(json)
resp = req.get_response(self.parent.proxy)
if resp.status_code != 200 and not (
resp.status_code == 500 and resp.content_type == "application/json"
):
raise ProxyError(
"Error from JSON-RPC client %s: %s" % (self.parent._url, resp.status),
resp,
)
json = loads(resp.body)
if json.get("error") is not None:
e = Fault(
json["error"].get("message"),
json["error"].get("code"),
json["error"].get("error"),
resp,
)
raise e
return json["result"]
class ProxyError(Exception):
"""
Raised when a request via ServerProxy breaks
"""
def __init__(self, message, response):
Exception.__init__(self, message)
self.response = response
class Fault(Exception):
"""
Raised when there is a remote error
"""
def __init__(self, message, code, error, response):
Exception.__init__(self, message)
self.code = code
self.error = error
self.response = response
def __str__(self):
return "Method error calling %s: %s\n%s" % (
self.response.request.url,
self.args[0],
self.error,
)
class DemoObject(object):
"""
Something interesting to attach to
"""
def add(self, *args):
return sum(args)
def average(self, *args):
return sum(args) / float(len(args))
def divide(self, a, b):
return a / b
def make_app(expr):
module, expression = expr.split(":", 1)
__import__(module)
module = sys.modules[module]
obj = eval(expression, module.__dict__)
return JsonRpcApp(obj)
def main(args=None):
import optparse
from wsgiref import simple_server
parser = optparse.OptionParser(usage="%prog [OPTIONS] MODULE:EXPRESSION")
parser.add_option(
"-p", "--port", default="8080", help="Port to serve on (default 8080)"
)
parser.add_option(
"-H",
"--host",
default="127.0.0.1",
help="Host to serve on (default localhost; 0.0.0.0 to make public)",
)
options, args = parser.parse_args()
if not args or len(args) > 1:
print("You must give a single object reference")
parser.print_help()
sys.exit(2)
app = make_app(args[0])
server = simple_server.make_server(options.host, int(options.port), app)
print("Serving on http://%s:%s" % (options.host, options.port))
server.serve_forever()
# Try python jsonrpc.py 'jsonrpc:DemoObject()'
if __name__ == "__main__":
main()
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