gepard-web

Web client for gepard (Browser, React, ...) General purpose communication and synchronization layer for distributed applications / Microservices / events, semaphores, locks and messages for JavaScript, Java, Python and PHP

• Overview
• Usecases
  • Updating a Customer-record in the Database

Overview

This JavaScript module implements a simple client for the GEPARD middleware for general purpose distributed applications to be used in a Web-Browser application or in a React/React-native application for browser, iPhone and Android app.

This GEPARD client can be used also within all JavaScript-based web-framworks. It connects a WebApp directly with the GEPARD middleware on the server-side. The connection is done with pure JavaScript WebSocket features without any helper-libs like socket.io or the like. With this technology high performance is guaranteed without any overhead.

Service requests, semaphores, locks, events in an GEPARD based communication layer are directly accessible. The WebSocket server is based on an appropriate node-module on the server side.

This WebSocket server can easily be plugged into a standard web-server like apache or nginx. Example configurations and many examples can be found in gepard on npm and gessinger-hj/gepard on github

Usecases

Updating a Customer-record in the Database

Suppose there is a database containing customer base-data like for example name, id, enabled,...

The access to the database for example is done with laravel/eloquent. The UPDATE is coded with the following code-snippet:

$customer_Id = 1 ;
$customer = App\Customer::find($customer_id);

$customer->name = 'New Customer Name';

$customer->save();

Interested 3rd parties now are informed by sending an Event:

Client::getInstance()->emit('CUSTOMER_CHANGED', ['CUSTOMER_ID' => $customer_id]);

Interested parties for example are:

• A Java program which sends an e-mail.

  Client.getInstance().on ( new String[] { "CUSTOMER_CHANGED" }, (e) -> {
  	Integer customer_id = e.getValue ( "CUSTOMER_ID" ) ;
  
  	*select customer from database with customer_id*
  	*use any mail-api to send mail*
  } ) ;

• A JavaScript program which sends an e-mail:

  gepard.getClient().on ( 'CUSTOMER_CHANGED', (e) => {
  	let customer_id = e.getValue ( 'CUSTOMER_ID' ) ;
  
  	*select customer from database with customer_id*
  	*use any mail-api to send mail*
  } ) ;

• A Python program which sends an e-mail:

  
  def on_CUSTOMER_CHANGED ( event ):
  	customer_id = event.getValue ( 'CUSTOMER_ID' ) ;
  
  	*select customer from database with customer_id*
  	*use any mail-api to send mail*
  
  gepard.Client.getInstance().on ( 'CUSTOMER_CHANGED', on_CUSTOMER_CHANGED ) ;

• A single page web-app or a React-native app

  gepard.getWebClient().on ( 'CUSTOMER_CHANGED', (e) => {
  	let customer_id = e.getValue ( 'CUSTOMER_ID' ) ;
  
  	if ( customer-data are displayed in any part of the page ) {
  		*select customer from database with customer_id via a REST call*
  		*update appropriate display*
  	}
  } ) ;