Services

Quite often, you will need to render the output of your application using a protocol other than HTML; for example, JSON or XML.

Emmett can help you expose those services with the service decorator:

from emmett import App
from emmett.tools import service

app = App(__name__)

@app.route("/json")
@service.json
async def f():
    # your code

The output will be automatically converted using the required service (JSON in this example).

– awesome. But, what if I need to expose several function with a service? Should I decorate every function?
– you can use the provided pipe, dude

Emmett also provides a ServicePipe object so you can create an application module with all the functions you want to expose with a specific service and add the pipe to the module:

from emmett.tools import ServicePipe
from myapp import app

api = app.module(__name__, 'api')
api.pipeline = [ServicePipe('json')]

@api.route()
async def a():
    # code

@api.route()
async def b():
    # code

So, which are the available services? Let's see them.

JSON and XML

Providing a JSON service with Emmett is quite easy:

@app.route("/json")
@service.json
async def f():
    l = [1, 2, {'foo': 'bar'}]
    return dict(status="OK", data=l)

The output will be a JSON object with the converted content of your python dictionary:

{
    "status": "OK",
    "data": [
        1,
        2,
        {
            "foo": "bar",
        }
    ]
}

To provide an XML service, just decorate your function using the next line instead:

@service.xml

Obviously, the syntax for using ServicePipe is the same as in the first example:

# providing a JSON service pipe
ServicePipe('json')

# providing an XML service pipe
ServicePipe('xml')

Multiple services

Sometimes you may want to expose several services for a single endpoint, for example a list of items both in JSON and XML format.

You can easily achieve this decorating your route multiple times, using different pipelines:

from emmett.tools import ServicePipe

@app.route('/elements.json', pipeline=[ServicePipe('json')])
@app.route('/elements.xml', pipeline=[ServicePipe('xml')])
async def elements():
    return [{"foo": "bar"}, {"bar": "foo"}]

With this notation, you can serve different services using the same exposed method.