This article covers some of the techniques that can be used to store and retreive application configuration data (Aka properties) in a Java application. It currently focuses on software that is deployed to an application server such as websphere.
This artical is not about the broarder configuration management topic also it won't tell you exactly to make use of the configuration data in your application. but it is related.
Most non trivial java applications need some mechanism to deal with environment related application properties. This article covers some techniques that can be used for storing and retreiving applicition configuration data*. It not and article about configuration management and it only touches on the details of how the applications actually use the properties. It will give an overview of some of the options avaliable. This focuses on an application server environment
Configuration data is mostly used as a list of key value pairs.
- No Configuration
- JVM properties
- Flat File
- Class path properties file
- Directly referenced properties file
- Ini files
- Resource environment provider (Within an application server)
- Environmental variables
No Configuration (Hard coding)
This is when the application data is kept directly within the application and any changes required for the application code to be changed and the application to be recompiled.
This is when you keep all your configuration data within the jvm. These values are usually accessed using the System.getProperty method
This is when the Data is put at the application / environment it can be globally for the operating sytem or with the id
Flat file (Aka properties file)
When a file is used to store the configuration data. The file can be within the application or outside of the application. There are a number of mechanisms to find these and two common approaches are to look them up using a System property to specify their location the other is to look for a class path relative file.
When a table is used within a database to keep the application configuration data usually there will be a table that has a column relating to the property / key and a coresponging the the value e.g.
|Key / Property||Value|
Resource Environment provider
In Websphere Appllication server 6.1 it is possible to store the properties within a resource environment provider. This enables the properties to be retreived as an object via a JNDI lookup the actual object retreived depends on the how the lookup is implemented but its a mechanism for storing properties.
Resource Environment Provider -> http://www.ibm.com/developerworks/websphere/library/techarticles/0611_totapally/0611_totapally.html
Commons Configuration -> http://commons.apache.org/configuration/
Database props -> http://www.springbyexample.org/twiki/bin/view/Example/SpringModulesWithCommonsConfiguration
Danielp 2009-04-01 - Initial release still work todo