I'm sitting in Jeff's talk now, getting ready to listen to him ramble on about Geronimo. The room is about half full, and it's one of the smaller rooms. However, people are still streaming in, and it's the furthest room from the main conference area.
Jeff started his presentation with a little "Open Source Arcade" fun. The cartoon depicted a pac-man game with JBoss and Geronimo and resulted in a loud applause from the audience. This talk is going to cover Geronimo's architecture, how to use it, how to configure it, what it doesn't have and address common concerns.
Geronimo is a conglomeration of best-of-breed open source projects. Rather than reinventing the wheel, Geronimo embraces and reuses other open source projects: Axis, MX4J, ServiceMix, Spring, ActiveMQ, Jetty, Tomcat, Derby, Tranql, Apache Directory Server and OpenEJB. There's many others, but these are the headliners.
Geronimo is a carpet roll. Just like a carpet, it allows you to roll-your-own application server. Rather than using all the pieces of J2EE, you can just pick the ones you need? Currently, Geronimo ships with a collection of pre-configured assemblies: j2ee-tomcat-server, j2ee-jetty-server, minimal-tomcat-server and web-jms-tomcat-server. The last two will be available in the 1.1 release. The nickname for minimal-tomcat-server is "Little G".
Why another J2EE application server? Because J2EE is now a commodity. You used to have to spend a lot of money for J2EE servers. Now open source projects have commodotize J2EE and flattened the landscape. Also, the other application servers are LGPL and Geronimo is Apache Licensed, which is much more friendly to businesses.
Geronimo isn't just an application server, but also a top-level apache project with a healthy and active community. There are many other components coming out of this project, including:
- The Geronimo API/Kernel/Assemblies/App Server
- GBuild - Open Source Testing
- DevTools - Eclipse Plugin for Geronimo Application Development with the Web Tools Platform (WTP)
- J2EE Specifications - open source versions, eliminating the jta.jar problem you get with Maven. In my experience, most of these work, but Geronimo's javamail implementation doesn't work last time I tested it.
- Home for OpenEJB, ActiveMQ, ServiceMix, Yoko (Corba) and XBean - all stand-alone sub-projects.
The Kernel of Geronimo *is* what is known as Geronimo. It controls the component (GBean) Lifecycle. A GBean is the Glue, the Wrapper, a Plugin to the Kernel. It conforms to JSR-77, the J2EE Management Specification and controls lifecycle, running states and naming conventions. The GBean architecture allows for simple development - you just need to implement the GBeanLifecycle, declare the GBean in a Plan (IoC) and deploy it. Plugging in 3rd party components is easy - for example Apache Directory and Quartz. Jeff wrote an article showing how to do this.
Jeff is now walking through the directory structure, which is pretty standard:
bin
config-store
deploy
docs
lib
repository (similar to Maven 1's structure)
schema
var
If you're familiar with Tomcat, Geronimo's "bin" directory is very similar. There's startup.sh/.bat, geronimo.sh and you can also use java -jar ./server.jar to start the server. Apparently, many of the scripts were copied from the Tomcat project.
Interestingly enough, my MacBook Pro's battery has been *much* more efficient today. I've been running for about 2.5 hours and the battery says it still has over an hour left. I believe this is largely because I've had my airport turned off most of the day.
Geronimo's Web Console is one of the nicer looking consoles I've seen for application servers. The user accounts for this are set in $GERONIMO_HOME/var/security/users.properties. It was donated by Abock (sp?) and I believe it's built on Pluto. For deploying applications, you can use the web console, drop WARs/EARs into the deployer directory or use the deployer tool (deployer.sh). When using the deployer tool, you'll need to have a plan file.
A plan file is an XML document (external or internal depending on nature of plan file). It's a descriptor to extend your application (setup JNDI DataSources, etc.) and similar to jboss-web.xml and weblogic.xml. Embedded examples: geronimo-application.xml, geronimo-web.xml, geronimo-ra.xml. For external plan files, you can use any name for the file. This file describes the GBean's attributes and references, as well as its dependencies. There are many different types of plans to describe information: web, application, resource adapters, security, naming references, EJB, schemas (in $GERONIMO_HOME/schemas directory).
The $GERONIMO_HOME/var/config/config.xml is Geronimo's central configuration file and allows you to override default values, as well as configure (or disable) GBeans. However, you can use the web console to configure everything in this file - and often it's much easier.
Now Jeff is going to do a demo of deploying and configuring Roller on Geronimo. This should be good, especially since he expects Murphy's Law, "if something can go wrong, it will", to come into play. He's showing us the plan file and how he had to hide a few classes, to prevent Geronimo's classes from conflicting. Jeff tried to show us how Geronimo allows you to download JDBC Drivers from w/in the console. Doh! We're in a conference room without an internet connection. Jeff had a backup plan and was able to successfully create a connection pool. After creating a security realm, he deployed roller.war and it all worked.
What Geronimo doesn't have? It lacks full clustering with respect to EJB/JNDI/Distributed cache. It *does* have full clustering with session replication and fail-over for the Tomcat web component, which fits 90% of clustering use cases. Uses Tomcat Clustering GBeans. Also, it can't run with Java 5 (only with 1.4.2) b/c the Corba component doesn't work with Java 5.
Now Jeff is doing Q&A, so I decided to try out my connecting to the Net via Bluetooth. It's actually pretty fast, GMail is surprisingly fast. From Bandwidth Speed Test, here are my results:
Communications: 87.1 kilobits per second
Storage: 10.6 kilobytes per second
1MB file download: 1.6 minutes
Subjective rating: Slow
