Entourage Service Brokers

One of the key components of a rich web client application like those you will create with Entourage is client/server communication. To help facilitate this communication, Entourage provides 'service brokers' that enable client/server RPC using a JSON data transport protocol.

The Entourage Service Brokers utilize the message oriented architecture provided by MQ to subscribe to and handle remote messages prefixed with r:, which stands for “Remote”. Remote messages are dispatched to the server, and routed to the proper handler methods by a Service Broker, of which we have implementations for a number of programming languages and frameworks (see the list at left).

Should you use the Service Broker or RESTful Web Services? It depends on the needs of your application. If you'd like to have a public interface to your back end services (like a Flickr or Google, for example), RESTful services might be a better choice. If your services primarily exist to service your web client application, then the Service Brokers will provide an easy to use RPC mechanism to invoke server-side logic. In either case, your services should be mostly stateless and atomic, so that you can realize the full benefits of a client/server architecture.

There are two ways of invoking remote services:

• Using the MQ JavaScript API
• Using Entourage Expressions

Consult the documentation for those components for help on invoking and handling remote services from the client side.

For every Service Broker implementation, there is a means of annotating functions or methods to allow them to subscribe to remote messages sent by the client. The syntax for these annotations varies based on the server-side programming language being used, but they generally follow a format like the following Java example:

@Service(request="hello.request", response="hello.response")
protected void hello(Message request, Message response) {
  String yourMessage = request.getData().getString("your_message");
  response.getData().put("message", yourMessage);
}

Click on the server-side programming language/framework of your choice to learn more about using them to implement remote services.