REST outgoing connections

REST outgoing connections allow one to invoke external REST-based endpoints.

  • URL paths can include patterns
  • Query string parameters are built from user-provided dictionaries
  • Payload can be automatically serialized to JSON or XML
  • Services can produce any and all headers the endpoint expects

For instance, let's assume that there is a POST REST endpoint at which expects:

  • A URL path in the format of /customer/{cust_id}/phone_no/{phone_no}
  • Query string ?priority=normal
  • JSON payload {"billing":"395.7", "currency":"EUR"}
  • Custom HTTP headers, X-App-Name: Zato and X-Environment: Production

An outgoing connection and a service using it would read as follows:

# -*- coding: utf-8 -*-

# Zato
from zato.server.service import Service

class SetBillingInfo(Service):
   """ Updates a customer's billing information.
   def handle(self):

         # Python dict representing the payload we want to send across
         payload = {'billing':'395.7', 'currency':'EUR'}

         # Python dict with all the query parameters, including path and query string
         params = {'cust_id':'39175', 'phone_no':'271637517', 'priority':'normal'}

         # Headers the endpoint expects
         headers = {'X-App-Name': 'Zato', 'X-Environment':'Production'}

         # Obtains a connection object
         conn = self.outgoing.plain_http['SetBillingInfo'].conn

         # Invoke the resource providing all the information on input
         response =, payload, params, headers=headers)


  • As a programmer you never need to leave Python land, (de-)serialization is automatic and one can work with Python dataclasses or dictionaries only

  • The response object offers access to the whole of the body, headers and other metadata that the endpoint returns

  • Accessing JSON endpoints can be further simplified using by the dedicated JSON adapter