Java Applet Architecture

The discussion that follows is general with respect to Applets that communicate through sockets with remote servers. It is oriented, however, toward the Comp 118 Assignment 1.

Basic WWW/Applet Architecture

HTML Required to Load Applet
<html>

<head>
<title>jbsServerThreaded</title>
</head>

<body>
<center>
<font color=AA0000>
<h3>jbsServerThreaded Running on Tomcat,  Host 152.2.128.10, port 8902</h3>
<h3>Applet Tag for jbsClientApplet Returned</h3>
</font>
</center>

<applet code=jbsClientApplet.class codebase=http://152.2.128.10:8888/Courses/comp118/applets/jbsClientApplet width=50 height=50>
<param name=host value=152.2.128.10>
<param name=port value=8902>
</applet>

</body>

</html>
    

WWW/Applet/Servlet Architecture

Example

Layered Architecture

Issues

Controlling complexity
Best Practices
Isolated, thin, internally coherent.

Layered Applet

as might be applied to WWW/Applet/Servlet Architecture

Layered Applet

additional details

User Interface Layer

Major Function

Map between UI (AWT/SWING) objects and more convenient data object (e.g., EntryObj).

Process UI events.

Update display.

Indicate status of transaction.

Interact with next layer down (Facade).

Issues

Define EntryObj.

Obtain status information.

Build helper methods.

Decide where to do main processing.

Facade Layer

Major Function

Provide a facade for the object supported by the server.

Support methods for interacting with the server object.

Map between basic data object (e.g., EntryObj) and objects to be sent to/from server (e.g., TransObject).

Interact with next layer down (Communication).

Issues

Facade for what?

Identify specific methods and return values.

Define TransObject.

Indicate method called within TransObject.

Respond to return code within TransObject.

Communication Layer

Major Function

Map between TransObj and Protocol.

Manage connection with the server.

Provide I/O form/to the server through the connection.

Issues

Open and close the connection.

Build helper methods.

Catch and respond to Exceptions.