B4J Tutorial [WebApp] Web Apps Overview

B4J v2.00 adds support for web applications based on WebSocket technology. With WebSocket The browser and the server maintain an open communication channel.
This channel allows us to build web apps where all (or most) of the logic is implemented in the server.

The new framework is implemented in jServer library. It adds a new type of "handler" named WebSocket.
The browser UI is implemented in html / css.

B4J Web App Goals

• Simple to build real-world web applications with the same libraries and similar code as done in B4J / B4A.
• Good performance.
• Very easy to extend.

You can see several online examples here: http://basic4ppc.com:51042/

The source code of all these examples is attached to this post.

What you need to know?

• Server library tutorial: [Server] Building web servers with B4J
  This tutorial was written before WebSockets were available.
• Html / CSS - Required for the UI.
• (recommended) Basic knowledge of jQuery. JQuery is a JavaScript library that simplifies access to html elements. B4J WebSocket client side implementation is based on jQuery.

Which browsers are supported?

All modern browsers support web sockets. See this table: http://caniuse.com/websockets
Android is a bit late here. The Chrome browser (compatible with Android 4.0+) supports web sockets.

How to deploy?

The compiled jar file is a standard Java app. The web server is embedded in this jar.
Any computer with Java 7+ installed can run it (including boards such as Raspberry Pi).
Shared hosting solutions will not work as they don't support Java. VPS solutions will work.
You can also turn a local computer into a public web server with a dynamic dns service:
http://www.basic4ppc.com/android/fo...r-b4j-server-over-the-internet.37201/#content
Tip: if you are running it in linux then you should use the nohup command.

Where do I go from here?

[WebApp] Hello World Web App
Other tutorials: http://www.basic4ppc.com/android/forum/pages/results/?query=webapp&page=1&prefix=18

The online examples project is attached.
The full project depends on a MySQL database (and several other libraries - see post #19).
You can start with the NoMySQL project which doesn't depend on MySQL.

 

The web server is online. Maybe your firewall blocks outgoing connections to non-standard ports.

 

No. The online examples are hosted on the site server (linux). Though you can host it on a Raspberry Pi board.

The libraries are listed at the end of the first post.

 

Great work!

Can you also post it in the share your creations or as a new tutorial (otherwise it will be more difficult to find)?

 

ServerExampleNoMySQL project was uploaded to the first post. This project doesn't depend on a MySQL database and is easier to start with.

 

This is a new method, not included in the beta. I will soon release v2.00.

 

The compiled jar is a web server itself. Jetty is embedded inside.
You just need to run it by double clicking on the jar or with java -jar <yourjar>

 

I recommend you to start with the ServerExampleNoMySQL project. It only depends on "core" libraries.

The full project depends on: jExcel, ByteConverter and Encryption library (last two are B4A libraries).
It also depends on the MySQL jdbc driver.

The performance should be very good. See some numbers here: [Server] Performance measures