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Getting Started with HTML5 WebSocket on Oracle WebLogic 12c

02.10.2014
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The current release of Oracle WebLogic (12.1.2) added support to HTML5 WebSocket (RFC-6455) providing the bi-directional communication over a single TCP connection between clients and servers. Unlike the HTTP communication model, client and server can send and receive data independently from each other.  The use of WebSocket is becoming very popular for highly interactive web applications that depend on time critical data delivery, requirements for true bi-directional data flow and higher throughput. To initiate the WebSocket connection, the client sends a handshake request to the server. The connection is established if the handshake request passes validation, and the server accepts the request. When a WebSocket connection is established, a browser client can send data to a WebLogic Server instance while simultaneously receiving data from that server instance. 
The WebLogic server implementation has the following components:
  •  The WebSocket protocol implementation that handles connection upgrades and establishes and manages connections as well as exchanges with the client. The WebLogic server fully implements the WebSocket protocol using its existing threading and networking infrastructure.
  • The WebLogic WebSocket Java API, through the weblogic.websocket package, allows you to create WebSocket-based server side applications handling client connections, WebSocket messages, providing context information for a particular WebSocket connection and managing the request/response handshake. For additional information about the WebLogic WebSocket Java API interfaces and classes, visit the following resource: http://docs.oracle.com/middleware/1212/wls/WLPRG/websockets.htm#BABJEFFD
  • To declare a WebSocket endpoint you use the @WebSocket annotation that allow you to mark a class as a WebSocket listener that's ready to be exposed and handle events. The annotated class must implement the WebSocketListener interface or extend from the WebSocketAdapter class.
When you deploy the WebSocket-based application on WebLogic, you basically follow the same approach using the standard Java EE Web Application archives (WARs), either as standalone or WAR module. Either way, the WebLogic Application Server detects the @WebSocket annotation on the class and automatically establishes it as a WebSocket endpoint.

Here is a simple application that creates a WebSocket endpoint at the /echo/ location path, receives messages from the client and sends the same message back to the client.
import weblogic.websocket.WebSocketAdapter;
import weblogic.websocket.WebSocketConnection;
import weblogic.websocket.annotation.WebSocket;

@WebSocket(pathPatterns={"/echo/*"})
public class Echo extends WebSocketAdapter{

@Override
  public void onMessage(WebSocketConnection connection, String msg){
      try{
          connection.send(msg);
      }catch(IOException ioe){
          //Handle error condition
      }
  }
}
n the client side, you typically use the WebSocket JavaScript API that most of the web browsers already support.

There are many samples out there that you can use to test the implementation above. One quick way of doing that is to navigate to http://www.websocket.org/echo.html and then point the location field to your WebLogic server. If you follow the sample available on https://github.com/mjabali/HelloWorld_WebSocket then you'll end up with something like ws://localhost:7001/HelloWorld_WebSocket/echo/ for the WebSocket server application.

The sample client provided will be available at http://localhost:7001/HelloWorld_WebSocket/index.html after the WebLogic deployment. See the README.md file on GitHub for additional instructions.

Have fun!
Published at DZone with permission of Marcelo Jabali, author and DZone MVB. (source)

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