globalenvironment
Project home

GlobalEnvironment

Overview

GlobalEnvironment is a global version of regular Properties  and Hashtable. java.util.Properties and java.util.Hashtable are valid within one single Java VM. GlobalEnvironment is valid across the whole network in distributed computing environment.

In the J2EE  world, the environment values are very rigid. The initial parameters for EJBs and JSPs are in deployment descriptors. They can be changed at deploy time only. They are not shareable among different distributed components. Using GlobalEnvironment as static values, you can make your program more flexible. GlobalEnvironment can be used as dynamic values as well. GlobalEnvironment is a family of utility classes. It consists of:

GlobalDouble

GlobalHashtable

GlobalLong

GlobalObject

GlobalProperties

Java threads

JVMs,

EJBs (Enterprise Java Beans)

JSPs (Java Server Pages)

Java applications

non-Java applications.

GlobalEnvironment is designed to be vender and platform neutral.

GlobalEnvironment has most of applicable methods from java.util.Properties and java.util.Hashtable. The method signatures are similar, but with a java.sql.Connection as the first parameter.

Other options

When we come to this point, you may say that there is a performance penalty to access database dynamically. Yes, compare to memory operation in a single JVM. But if you want the key-value pairs valid across the network for different JVMs, you need to keep them in a central place. If you want them to be persistent, you need to store them in a data source. Database is the best choice. 

Some programs store user object in JNDI tree. But that is even more expensive. Many clustering use multicast for clustering communication. Storing large objects within the JNDI tree can overload multicast traffic and interfere with the normal operation of a cluster. 

There is a new class Preference in JDK 1.4. But neither JNDI or Preference will allow you to combine environment changes and your business data changes in one transaction, so you can not COMMIT or ROLLBACK.

Thread safe and thread friendly

The methods increase in both GlobalDouble and GlobalLong provide a thread friendly functionality on top of thread safe behavior: a thread will not overwrite changes from other threads. For example, you have an attribute "totalSale". The current value is 10.00. Now you sold something for 2.00 and your coworker sold something for 5.00 at the same time. If you do:

  
    read totalSale and get the value 10.00
    write totalSale as 10.00 + 2.00
 

    increase by 2.00
 

Other information

There is some related information:

• Open source projects at Acelet
• SuperEnvironmentLite
• Environment variables in J2EE world