A Quick Look at JBoss Internals
Since Version 3.0, JBoss has been built around a few very powerful concepts that allow users to customize and fine-tune their servers for very specific needs, not limited to J2EE. This flexibility allows JBoss to be used in very different environments, ranging from embedded systems to very large server clusters. The next few sections comment on some of these concepts briefly.
Microkernel Architecture
JBoss is based on a microkernel design in which components can be plugged at runtime to extend its behavior.
This design fits particularly well with the J2EE platform, which is essentially a service-based platform. The platform contains services for persistence, transactions, security, naming, messaging, logging, and so on.
Other application servers are generally built as monolithic applications containing all services of the J2EE platform at all times. JBoss takes a radically different approach: each of the services is hot-deployed as a component running on top of a very compact core, called the JBoss Server Spine (Figure W-2). Furthermore, users are encouraged to implement their own services to run on top of JBoss.
Tip
Consequently, the JBoss application server is not limited to J2EE applications, and indeed is frequently used to build any kind of application requiring a strong and reliable base. For this reason, the JBoss core is also known as the WebOS .
Figure 21-2. JBoss Server Spine with some hot-deployed services
JBoss Server Spine itself is based ...
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