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Tuscany - Learning More - Binding Websocket - Autocomplete Webapp
-----------------------------------------------------------------
This sample demonstrates how Tuscany can expose services via websockets as well
as how to interact with them using Tuscany's javascript API.
This project contains a service (CountryService) that handles requests asking
for country names starting with a certain prefix. The service implementation
uses a country repository to fetch the necessary data.
By adding <tuscany:binding.websocket port="8090"/> to a service definition, the
Tuscany runtime will start a websocket server listening for requests coming
in for the exposed service at the specified port. If no port is specified, the
runtime will use port 9000 as a default.
The websocket binding uses embedded Jetty instances as websocket servers. At the
moment, Jetty 8.0.0-M3 is used which has support for the 00, 01, 06 and 07
versions of the websocket protocol drafts.
IN ORDER TO RUN THIS SAMPLE SUCCESSFULLY PLEASE CHECK IF YOUR BROWSER SUPPORTS
THE ABOVE WEBSOCKET PROTOCOL VERSIONS AND THAT THE WEBSOCKET SUPPORT IS ENABLED.
The websocket binding also features a javascript API to simulate SCA in the
browser. In order to use it, the following script has to be included in the
client page:
<script type="text/javascript"
src="org.apache.tuscany.sca.WebsocketComponentContext.js">
</script>
This will inject proxies for all services defined in the composite that are
using binding.websocket. All invocation and connection management is handled
under the hood so in order to invoke a websocket service, the following should
be called:
Tuscany.WebsocketComponentContext.<component name>.<service name>.<operation name>(<parameters>);
Given the asynchornous nature of websockets, a function should be defined in
order to handle responses received for a certain service operation. This should
be done as follows:
Tuscany.WebsocketComponentContext.<component name>.<service name>.<operation name>.responseHandler = function(response) {
// handle response
};
Note that the data exchange is automatically handled by the binding, so the
parameters should have the same structure as the data types defined in the method
definition. Also, the response will have the same data type as the return type of
the service method. Objects are passed over the wire in JSON format.
Another detail worth mentioning is that the binding will use a single websocket
connection to handle communication between a browser client and all services
defined using binding.websocket on the same port. Requests and responses will get
multiplexed via the same channel and get routed to the appropriate service
implementation, respectively javascript function.
In order to run the sample, you can execute "mvn jetty:run" which will start a Jetty
instance automatically or use "mvn package" and deploy the resulting war to the
application server of your choice.
Next, point your browser at
http://localhost:8080/sample-binding-websocket-autocomplete-webapp/
You can see how suggestions are being received in real time when characters are
entered in the text field. You can see the persistent websocket connection using
the developer tools provided by your browser.
The websocket binding is an experimental binding so community feedback is much
appreciated. Feel free to send comments or suggestions on the Apache Tuscany
dev mailing list (dev@tuscany.apache.org).
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