Understanding WLST built-in variables . . .[WLST scripting Best Practices (Part-5)]

This post is a continuation of my previous post - in a series of posts about WLST scripting best practices.

Managed Beans (MBeans) are used to represent all the configuration and runtime information about WebLogic Domain, Servers, the applications and services deployed on a WebLogic Server Domain. While you can get all the information from WebLogic MBeans, WLST simplifies the task of building scripts by providing some built-in variables. These WLST variables are initialized and/or modified when you change to online mode (connect to a server), start an edit session etc. to appropriate values.

One of the very useful WLST variable is cmo. cmo stands for current management object. When navigating in WLST you can use cmo to reference the current MBean (object) instance you are navigating into. The cmo value is changed when you navigate to different hierarchy of MBeans under different MBean trees in WebLogic (except jndi tree). The following illustrates the use of cmo.

...
connect(username, password, url)
edit()
startEdit()
cd('/Servers/server1')
s1=cmo
cd('/Servers/server2')
s2=cmo
print 'Listenport of server1 -> ' + s1.getListenPort()
print 'Listenport of server2 -> ' + s2.getListenPort()
...

Notice the use of cmo can for invoking operations on the respective MBean object. There are many such variables that will help you to write better and efficient WLST scripts. See here for the list of all the WLST variables.

If you know a variable name you can simply use it in you script. dumpVariables() command can be used to list all the variables and their values.

wls:/testdomain/serverConfig> dumpVariables()
adminHome                     weblogic.rmi.internal.BasicRemoteRef - hostID: '328889774891021637S:127.0.0.1:[7001,7001,-1,-1,-1,-1,-1]:testdomain:AdminServer',oid: '259', channel: 'null'
cmgr                          [MBeanServerInvocationHandler]com.bea:Name=ConfigurationManager,Type=weblogic.management.mbeanservers.edit.ConfigurationManagerMBean
cmo                           [MBeanServerInvocationHandler]com.bea:Name=testdomain,Type=Domain
connected                     true
domainName                    testdomain
...

In addition you should also be aware of these WLST variables in order to NOT use them to store your own information. If you do so then WLST will overwrite these variables during your interaction like connect, startEdit etc. So make sure you understand these WLST variables, use them in your scripts and do not use them to store your information.