Clustering And Performance - Red Hat APPLICATION SERVER - JONAS Manual

Chapter 1. Java Open Application Server (JOnAS): a J2EE Platform
be compared to the
CATALINA_HOME
is dedicated to JOnAS installation,
figuration.
JONAS_BASE
tifies subdirectories containing the EJB-JAR, WAR, EAR, and RAR files that can be loaded in this
application environment. There is an ANT target in the JOnAS
directory structure. Thus, from one JOnAS installation, it is possible to switch from one
JONAS_BASE
application environment to another by just changing the value of the
There are two ways to configure a JOnAS application server and load applications: either by using the
administration console or by editing the configuration files. There are also "autoload" directories for
each type of application and resource (EJB-JAR, WAR, EAR, RAR) that allow the JOnAS server to
automatically load the applications located in these directories when starting.
JOnAS provides several facilities for deployment:
For writing the deployment descriptors, plugins for Integrated Development Environments (IDE)
•
provide some generation and editing features (Eclipse and JBuilder plugins are available). The
NewBean JOnAS built-in tool generates template deployment descriptors. The Xdoclet tool also
generates deployment descriptors for JOnAS. The Apollon ObjectWeb project generates Graph-
ical User Interfaces for editing any XML file; it has been used to generate a deployment de-
scriptor editor GUI (see http://debian-sf.objectweb.org/projects/apollon). A deployment tool de-
veloped by the ObjectWeb JOnAS community, earsetup (http://sourceforge.net/projects/earsetup),
will also be available for working with the JSR88-compliant (J2EE 1.4) deployment APIs provided
by the ObjectWeb Ishmael project (see http://sourceforge.net/projects/earsetup/ and http://debian-
sf.objectweb.org/projects/ishmael/ respectively.
Some basic tools for the deployment itself are the JOnAS GenIC command line tool and the cor-
•
responding ANT EJB-JAR task. The IDE plugins integrate the use of these tools for deployment
operations. The main feature of the Ishmael project will be the deployment of applications on the
JOnAS platform.
1.4.2. JOnAS Development Environments
There are many plugins and tools that facilitate the development of J2EE applications to be deployed
on JOnAS. IDE plugins for JBuilder Kelly (http://forge.objectweb.org/projects/kelly/), JOPE
(http://forge.objectweb.org/projects/jope/), and Lomboz (http://lomboz.objectweb.org) provide the
means to develop, deploy, and debug J2EE components on JOnAS. The Xdoclet code generation
engine (http://xdoclet.sourceforge.net/) can generate EJB interfaces and deployment descriptors
(standard and JOnAS specific ones), taking as input the EJB implementation class containing
specific JavaDoc tags. The JOnAS NewBean tool generates templates of interfaces, implementation
class, and deployment descriptors for any kind of EJB. Many development tools may work with
JOnAS; refer to the JOnAS tools page at http://www.objectweb.org/jonas/tools.html for more details.
In addition, JOnAS is delivered with complete J2EE examples, providing a
all the necessary targets for compiling, deploying, and installing J2EE applications.

1.5. Clustering and Performance

Clustering for an application server generally makes use of three features: Load Balancing (LB), High
Availability (HA), and Failover. Such mechanisms can be provided at the Web-container level by
dispatching requests to several Servlet/JSP engine instances, at the EJB-container level by dispatching
EJB requests to several EJB container instances, and at the database level by using several databases.
A replicated JNDI naming is also necessary.
JOnAS provides Load Balancing, High Availability, and Failover at the WEB container level using
the Apache Tomcat mod_jk plugin and an HTTP-in-memory session-replication mechanism based
and
CATALINA_BASE
JONAS_BASE
designates a directory containing a specific JOnAS configuration, and it iden-
variables of Tomcat. While
is used to specify a particular JOnAS instance con-
build.xml
JONAS_BASE
JONAS_ROOT
file for creating a new
variable.
ANT file with
build.xml
11