What Is Geronimo?by Kunal Jaggi
- Geronimo is the newest Apache-initiated, open source application server. Licensed under the Apache license (version 2.0), Geronimo is a Java EE 1.4 certified app server.
In This Article:
- Why Geronimo?
- A Look Under the Hood
- Get Started with Geronimo
- Sample Application
- Deployment Plans
- Code Your First Geronimo App
- Build the App
- Deploy the App
- Test the App
Based in an integration of best-of-breed open source technologies, and with a vibrant and thriving community backing a certified open source server, Geronimo is set to take the enterprise market by storm. This article will introduce you to Geronimo and give you the basics you need for developing and deploying a simple Java EE web application on Geronimo.
Geronimo is not the only open source app server available in the market. There are other open source Java EE app servers out there as well, such as JOnAS from ObjectWeb. However, Geronimo fills a need that other application servers do not. With Geronimo, components can be easily integrated. Its key aim is to support custom builds, geared to the needs of specific applications. Geronimo offers choices. For instance, if you don't want transaction management, you can go for a web-tier container such as Tomcat or Jetty. Geronimo supports the assembly of custom components pretty easily. In short, you can make it whatever you need it to be. This means Geronimo is much more than simply an app server; it offers a framework that can be used to glue together different components.
Geronimo doesn't try to reinvent the wheel, and it's not a rip-off of any of the existing open source frameworks or tools. Rather, Geronimo is an integration of several open source projects, some of which are shown below:
|Tier||Open source project||Description|
|Web tier||Tomcat||Reference implementation for Java Servlet 2.4 and JavaServer Pages (JSP) 2.0.|
|Jetty||A web-tier servlet container that supports Servlets and JSPs.|
|Business tier||OpenEJB||An open source Enterprise JavaBeans container that also supports Container Managed Persistence 2 (CMP2) and EJB Query Language (EJBQL).|
|EIS tier||ActiveMQ||Open source Java Message Service (JMS) applications provider and supporter of message driven beans (MDBs).|
|HOWL||Distributed transactions and support for transaction logging.|
One of the most elegant features of Geronimo is that it doesn't require a restart. Unlike other web- and business-tier containers, which require restarting the container for any configuration change, Geronimo is tailored from the ground up to support dynamic class loading, and keeps running as an uninterrupted service.
A Look Under the Hood
Geronimo is a loose integration of components called Geronimo Beans or simply GBeans. GBeans, which are the building blocks of Geronimo, are managed beans based around an IoC container concept, and they're used to add services to the Geronimo kernel. Almost everything in Geronimo is a GBean.
It's easy to extend Geronimo by deploying new GBeans. GBeans define the capabilities of the server and are registered with the kernel as they are deployed. The GBean components follow a particular life cycle as the kernel creates them, injects dependencies, notifies events, and calls their methods. Each GBean can maintain a state, depend on other GBeans, and contain logic that defines its functionality. The GBean architecture is a Dependency Injection (DI) configuration and management system. A GBean is plugged to the kernel through a plan, which is an XML-based configuration file. Further, components can be easily removed by editing the configuration files. For more information on Geronimo GBean architecture and IoC containers, refer to the Resources section.
Get Started with Geronimo
Geronimo requires Java SE 1.4 (or higher, but earlier than SE 5). The latest milestone release available as of this writing is M5. Unzip the Geronimo with Tomcat container zip at some location, and set the GERONIMO_HOME environment variable to this location.
Start Geronimo by booting its kernel. Once started, Geronimo will load all predefined modules along with any other application modules as shown below (for brevity, not all fields are shown here):
D:\>cd %GERONIMO_HOME% D:\geronimo-1.0>java -jar bin/server.jar Booting Geronimo Kernel (in Java 1.4.2_08)... Starting Geronimo Application Server [********************] 100% 44s Startup complete Listening on Ports: 1527 0.0.0.0 Derby Connector 8080 0.0.0.0 Tomcat Connector HTTP 8443 0.0.0.0 Tomcat Connector HTTPS Started Application Modules: EAR: geronimo/daytrader-derby-tomcat/1.0/car EAR: geronimo/uddi-tomcat/1.0/car WAR: geronimo/welcome-tomcat/1.0/car Web Applications: http://WINKJ185011-NZR:8080/ http://WINKJ185011-NZR:8080/console Geronimo Application Server started
Next, verify the Geronimo installation by accessing the Geronimo console window at http://localhost:8080/console, as shown in Figure 1 below. Use the default username (
system) and password (
manager). Stopping Geronimo is easy;
Ctrl-C stops the app server.
Figure 1. Apache Geronimo Console