Synchronous Active Objects
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Introduction

The Laboratory of Teleinformatics has been studying the engineering of interactive software applications, namely applications that must react to events produced by the GUIs (graphical user interfaces) and the network, for many years.

This type of applications is usually made with the help of listeners, but listeners make it very difficult to understand a program's structure after it has been completed, and thus to debug and maintain software applications.

We took thus inspiration from the theories addressing concurrency to develop a framework and methodologies that could help us better this situation. We ended up with a concept of synchronous active objects, described in these pages.

20 lines to describe a synchronous active object 

Two trivial examples

Development Environment and Libraries for Synchronous Active Objects

Introduction to the synchronous active objects

• Synchronous Active Objects (An introduction to the concept)
• Try this debugger. It is very simple to use. It will give you a good idea of how synchronous objects run.
• Compatibility with Java. The available compiler produces a pure Java code when the option -p is on. Moreover, it is not too difficult to code the synchronous calls by hand (... or head !).
• An analyzer (This tool detects deadlocks)
• Analysis of Synchronous Active Objects (A connection between practice and theory)
• Summary of the Statement Syntax
• Event Programming    Description of the problems raised by event programming and a solution that constitutes an intermediary step into the synchronous world.
• Comparison between a program based on the MVC and the PAC pattern ( JavaWorld reference, local mirror) With the same application built with synchronous active objects.

Support and libraries

• Downloading the compiler, the libraries and the generator (Compiler developped at the LAMP, by Matthias Zenger).
• Display generator and synchronous GUI elements : a presentation of our synchronous GUI elements and of a generator that helps using them (see the javadoc).
• TCP sockets Library of synchronous active TCP sockets. It is very easy to handle these sockets in an asynchronous manner (see the javadoc).
• Active RMI stub generator : generation of stubs under the form of synchronous active objects. The generator delivers a set of classes that correspond to a runnable prototype. (still under test).
• Embedded version of Tomcat : There is an embedded partial version of Tomcat in the standard package that does not use any XML compilers nor support. We completed that program and packaged it to provide a simple HTTP access to any application. The accesses offered by this server can be located in the same program as the modules described above.

A Generator of Distributed/Interactive Applications

• This generator allows a developer to create an applications comprising GUIs (Display User Interfaces), RMIs (Remote Method Invocations), local or remote databases, coordinated with controllers that are built like standard objects, but have the power of parallel processes.
  These controllers can manage all the other components, even while they have a non-deterministic behavior. They can await several events in parallel to the select statement. download

Condensed documentation of some important standard Java libraires

• Collections and maps This is a short synoptic documentation on the collection and map libraries offered by the Java environment that should allow a developer to determine quickly which component fits best in a given situation.
• Streams This page provides an overview of the streams, classifying the stream classes as sources, sinks and filters within tables, which allows a quick selection of the classes that realize the service the developer looks for.

References

The sC++ book (English version.ps / with its index ) -- (Version française)

Synthesis paper: (IEEE Computer)

C. Petitpierre, Implementing Protocols with Synchronous Objects, in ed. D. Avresky, Dependable Network Computing, Kluwer, November 1999, pp. 109-140.

C. Petitpierre, A. Eliens, Active Objects Provide Robust Event-Driven Applications, SERP'02, Las Vegas, June 2002. Corresponding powerpoint presentation.

C. Petitpierre, Synchronous Active Objects Introduce CSP's Primitives in Java, CPA'2002, Reading, 15-18 September 2002, IOS-Press, pp. 109-122. Corresponding powerpoint and pdf presentation.

Related links

JCSP : an introduction of CSP into Java

CTJ : another introduction of CSP into Java

WoTUG: a forum about CSP and concurrency