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WebSphere sMash Screenshot running
1.1.1 / June 1, 2009
WebSphere sMash was a development and runtime environment from IBM for the creation of dynamic web applications using the scripting languages Apache Groovy and PHP. It contains a PHP runtime written in Java. Project Zero is the experimental software development community in which new versions of WebSphere sMash are incubated.
There are a number of distinguishing aspects to the architecture of WebSphere sMash.
Event-driven programming model
WebSphere sMash uses an event-driven programming model. Applications are typically composed of a number of small modules which communicate with each other by firing events which are then caught by other handlers that have registered to catch the events. The code firing the event does not have any knowledge of the code that will handle the event. This architecture allows application to be built up from a mixture of code written using PHP, Java, Groovy or the Flow language.
Since events are stateless, a mechanism is required to share data between event handlers. This mechanism is the Global Context. The Global context functions basically as a large map of data divided up into various zones with different lifetimes, properties and persistence.
Repository management system
sMash makes use of the Ivy dependency manager. sMash applications are composed of models which can specify dependencies on other modules which may be present in a local Ivy repository or which can be fetched from a remote repository. IBM maintains a repository of useful modules at projectzero.org and dependencies can also be specified on the maven2 repository.
The PHP support in WebSphere sMash is provided by a PHP runtime implemented in Java. PHP scripts are compiled into Java bytecode which then run on the Java Virtual Machine (JVM). This is similar in concept to the approach taken by other projects such as JRuby and Jython, which run the Ruby and Python languages, respectively, against the JVM. Running on the JVM allows direct, same process calls between PHP, Java and Groovy code allowing applications to be assembled using a variety of languages.
In contrast to the approach taken by Quercus, the other JVM based PHP implementation, sMash is able to re-use existing PHP extensions from PHP.net attaching them to the Java virtual machine via the Java Native Interface (JNI) and an API layer called XAPI-C.
The PHP runtime does not have an identity outside of sMash so it is simply referred to as the "WebSphere sMash runtime for PHP."
The PHP runtime supports close integration with the Java and Groovy languages through its Java/Groovy bridge. This allows PHP scripts to use libraries written in Java and Groovy through a lightweight and extremely fast interop layer. The Groovy bridge allows advanced features from Groovy to be accessed directly from PHP. Examples include closures and Groovy metaobjects.
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