Since Sun decided to open-source most of its Java-related software, projects hosted on java.net have become magnets of both new and interesting Java source code, and of developers interested in specific Java technologies.

Among the biggest java.net projects, both in terms of the code base it manages and the number of developers involved, is GlassFish. As a new Sun white paper, The Glassfish Community Delivering a Java EE Application Server (PDF document), explains, the initial focus of GlassFish was to provide an open-source reference implementation of the Java EE specifications. The project's main product, the GlassFish application server, is that reference implementation. However, GlassFish now includes technologies beyond the Java EE specs, says the newly published article:

GlassFish is a Community and an Application Server. The community's main deliverables are a Java EE 5 compatible Application Server, the GlassFish AppServer, and the Reference Implementation for the Java Persistence API, TopLink Essentials...

A year and a half after the initial launch, the GlassFish community has already delivered its first final release and is on its way to its second...

The GlassFish Community also delivers many other useful components including reusable modules for JCP technologies included in Java EE 5, like JAXB, JAX-WS, JAXP, StAX, JSP and JSF. GlassFish also includes several popular Web.Next projects like jMaki, Phobos and DynaFaces, many tools, like the Continuous Integration tool Hudson, and useful infrastructure like Grizzly[,] the NIO-based server framework. The GlassFish community also maintains a Maven repository for all these components.

What's your experience with the GlassFish application server? Would you, or have you, used it in a production environment?