Thursday, May 7, 2015

Oracle MAF and WebSockets Integration - Live Twitter Stream

Oracle MAF and WebSockets - I will describe how it works together. WebSockets is a protocol providing full-duplex communication channel over a TCP connection. This channel is interactive (communication is both ways) and we can send messages from the server to the client (MAF application running on the device). There is no need to use push notifications, WebSockets provide JSON support and allow to send complex payload data. In a way it competes with REST, however REST is different with request is being initiated by the client. WebSockets data is received automatically - there is no need to trigger any event by the client.

I have implemented sample MAF application with WebSockets integration, you can download it here - Finance screen in the application contains MAF output text component. This component displays latest data received through WebSockets channel. Server side is listening for live Twitter Stream updates and sends each tweet location over WebSockets to the MAF application. See how it works in this screen recording:

WebSockets communication is not blocking MAF application functionality, it runs in the separate thread. User can navigating between MAF screens, run different actions and WebSockets delivers data in parallel.

Sample applications is based on two parts - server side WebSockets implementation with Twitter Stream listener and client side MAF application with WebSockets client.

Twitter Stream is handled with Twitter4J API, JAR's are included with the sample. You would need to provide your own Twitter account details, access keys could be retrieved for your account from Twitter developer portal. Make sure to obtain these keys, before running sample application:

New message from Twitter Stream is received by listener method - onStatus. I'm listening for all the tweets around the world, related to corporate keyword. Once there will be new tweet related to this topic, onStatus listener will be notified. In the listener method, I'm retrieving tweet location and and initiating WebSockets communication:

Method in WebSockets implementation - notifyClient, sends text message to the client (JSON message is supported as well):

Listener for Twitter Stream is started automatically, when application is deployed. This is done through servlet initialisation:

On the client side - MAF application is configured to receive automatic notifications through WebSockets channel. Implementation for WebSockets listener is very similar with the regular ADF Faces - it is done through JavaScript. MAF feature is registered with JavaScript file:

JavaScript contains all required methods for WebSockets communication. Here we open WebSockets channel with connectSocket function and further listen for the new messages/notifications with onMessage method. My goal is to update MAF components with the new data received through WebSockets. For this reason, I'm invoking Java method from onMessage JavaScript function and passing payload data (recently received tweet location):

Invoked Java method - processWebSocketMessage is responsible to update MAF bindings with the new data. Data Bindings class contains standard MAF propertyListener implementation, which ensures data refresh on MAF UI:

MAF output text on the UI displays recent data received through WebSockets channel:

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