WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

► Environment-specific
This category includes configuration options that are specific to a deployment
environment but common to all applications running in that environment. This
category includes, for example, the name of the temp folder if applications
need to store temporary information. In the Windows development
environment, this might be C:\temp, but in the UNIX production environment,
it might be /tmp. This category of options must not move between
environments.
8.10.2 Managing configuration setting
Dealing with configuration settings is usually a major challenge for both
developers and system administrators. Not only may configuration settings have
to be changed when the application is moved from one deployment environment
to another, but the settings must also be kept in sync among all application
instances if running in a clustered environment.
To manage the settings stored in the WebSphere configuration repository (such
as the JVM maximum heap size), it is common to develop scripts that are run as
part of an automatic deployment to configure the settings correctly after the
application has been deployed. The values suitable for the application can be
stored in a bill of materials file inside the EAR file. This file can then be read by
scripts and used to configure the environment.
Settings stored in the deployment descriptors usually do not have to be changed
as the application is moved between different environments. Instead, the Java
EE specification separates the developers’ work from the deployers’. During
deployment, the resources specified in the deployment descriptors are mapped
to the corresponding resources for the environment (for example, a data source
reference is mapped to a JNDI entry, which points to a physical database).
Application-internal configuration settings, however, are often stored in Java
property files. These files are plain text files with key-value pairs. Java has
provided support for reading and making them available to the application using
the java.util.Properties class since Java 1.0. Although you can use databases,
LDAP, JNDI, and so on to store settings, plain Java property files are still the
most common way of configuring internal settings for Java applications. It is an
easy and straightforward method to accomplish the task. In a clustered
environment where the same application runs on multiple servers distributed
across different machines, care must be taken as to how to package, distribute,
and access the property files.
302 WebSphere Application Server V7.0: Concepts, Planning, and Design