dizzydecor is a python library that makes it easy to create web services in tornado. To accomplish this, the library adds two new classes and decorators that help eliminate the need for boilerplate code.
- Support for handler initialization with keyword arguments to the
webservicedecorator - Added support for path arguments (anything included in the url after the method name is added to a path_args list that will be passed to the called method)
- Custom service paths (use the path keyword argument in the
webservicedecorator) - Custom method names (use the name keyword argument in the
servicemethoddecorator) - Bypass body parsing on a per-method basis with the ignore_body keyword argument on the
servicemethoddecorator
Here is an example to show how dizzydecor, works:
from tornado.ioloop import IOLoop
from dizzydecor import (
WSApplication,
WebserviceHandler,
webservice,
servicemethod
)
# The webservice decorator accepts keyword argument that will be used in
# the handler's initialize method
@webservice(greeting="This is my custom greeting")
class MyWebService(WebserviceHandler):
def initialize(self, greeting):
self.greeting = greeting
@servicemethod()
async def echo(self, message):
return f"You said: {message}"
@servicemethod(httpmethod="GET")
async def my_greeting(self):
return dict(greeting="Hello, welcome to my web service demo!")
# Use the name argument to setup custom method names
# anything included in the url after the method name is sent to the
# method in an array named path_args
@servicemethod(ignore_body=True, name="greet")
async def my_other_greeting(self, path_args):
# with ignore_body set to True, you can parse the body yourself
body = self.request.body.decode("utf-8")
return dict(greeting=self.greeting, body=body, path_args=path_args)
# The path argument allows you to configure a custom path for this webservice
@webservice(path=r"/custom-name/(.+)")
class TotallyNonsensicalName(WebserviceHandler):
@servicemethod()
async def echo(self, message):
return dict(message=message)
if __name__ == "__main__":
app = WSApplication()
app.listen(8080)
IOLoop.current().start()This will create two web services. The first has three methods: echo, my_greeting, and my_other_greeting.
By default, service methods respond to POST requests; however, the httpmethod
argument to servicemethod can change this behaviour. For instance,
my_greeting is setup to respond to GET requests.
- Paths are generated based on class and method names.
- A web service's path is the lower-case class name with each word joined by a hyphen. (MyWebService -> my-web-service)
- A method's path is the method's name with underscores replaced with hyphens. (my_greeting -> my-greeting)
- Paths can also be configured manually.
- The
pathargument can be used with thewebservicedecorator to configure the web service's base path - Method names can be configured with the
servicemethoddecorator'snameargument
- The
If a service method does not get all of its arguments, the service handler sends a 400 HTTP status code automatically.
To test, you can use curl:
$ curl http://localhost:8080/my-web-service/echo -d '{"message": "This is my message"}'
"You said: This is my message"
$ curl http://localhost:8080/my-web-service/my-greeting
{"greeting": "Hello, welcome to my web service demo!"}
$ curl -d '{"a": 1}' http://localhost:8080/my-web-service/greet/t
{"greeting": "This is my custom greeting", "body": "{\"a\": 1}", "path_args": ["t"]}
$ curl -d '{"message": "test"}' http://localhost:8080/custom-name/echo
{"message": "test"}
$ curl -d '{"messag": "test"}' http://localhost:8080/custom-name/echo
"<html><title>400: Bad Request</title><body>400: Bad Request</body></html>"
You may have noticed that the example uses JSON.
In this case, all you need to do is override the load and dump
methods in a subclass of WebserviceHandler or SyncWebserviceHandler
Here is an example with PyYAML:
# -- snip --
import yaml
class YAMLServiceHandler(WebserviceHandler):
def load(self, request):
return yaml.safe_load(request)
def dump(self, response):
# You can also set content-type here with self.set_header
return yaml.safe_dump(response)
@webservice()
class YetAnotherService(YAMLServiceHandler):
@servicemethod()
async def join(self, arr, delim):
return dict(message=delim.join(map(str, arr)))
# -- snip --The rest is exactly the same, except now your service will use YAML.
Here's how to test it with curl:
$ curl http://localhost:8080/yet-another-service/join --data-binary @"/dev/stdin"<<_eof_
arr:
- Hello
- world
delim: " "
_eof_
message: Hello world
Install with pip or easy_install:
$ pip install dizzydecor
dizzydecor is only available for Python 3
In this case, all you need to do is extend the SUPPORTED_METHODS property of the service handler class.
# -- snip --
@webservice()
class NotificationService(WebserviceHandler):
SUPPORTED_METHODS = WebserviceHandler.SUPPORTED_METHODS + ("NOTIFY",)
@servicemethod(httpmethod="NOTIFY")
async def notification(self, message):
# etc
# -- snip --The script for the new HTTP method is added to the service handler during the creation of the web service. After that, all you need to do is setup to service method to respond to that request type. Depending on the situation, you might also need to customize the way arguments are parsed by overriding prepare.
If you want to add a handler that does not fit the web service mold, you can append it to the WSApplication's endpoints class variable. For example, maybe you want to add a websocket:
ws_clients = []
msg_buffer = []
class EchoWebSocket(WebSocketHandler):
def open(self):
print("WebSocket opened")
ws_clients.append(self)
for msg in msg_buffer:
self.write_message(msg)
def on_message(self, message):
global msg_buffer
message = u"Someone said: " + message
msg_buffer = msg_buffer[:19]
msg_buffer.append(message)
for client in ws_clients:
client.write_message(message)
def on_close(self):
print("WebSocket closed")
ws_clients.remove(self)
def check_origin(self, origin):
return True
if __name__ == "__main__":
WSApplication.endpoints.append((r"/websocket", EchoWebSocket))
# The keyword arguments websocket_ping_interval and websocket_ping_timeout
# are passed to the underlying Application class
app = WSApplication(websocket_ping_interval=3, websocket_ping_timeout=5)
app.listen(8080)
IOLoop.current().start()Any web services you added with dizzydecor decorators will still work.
The WebserviceHandler is asynchronous; however, you can make synchronous
service handlers using the SyncWebserviceHandler class.
# -- snip --
@webservice()
class MySyncService(SyncWebserviceHandler):
# This time the method is not async
@servicemethod(httpmethod="GET")
def my_greeting(self):
return dict(greeting="Hello...")
# -- snip --