Thursday, October 2, 2008

Make WLST scripts more flexible with Python's Getopt

My impression is that the audience of people who are learning and using the WebLogic Scripting Tool are not experienced Python programmers (I'm not, either). That's unfortunate, because Python (and Jython) have a lot of capabilities that can enhance your WLST scripts.

A natural "first script" in WLST probably hardcodes all the values that you might pass as command-line parameters in an ordinary shell script or Java class. Doing that limits the flexibility of your script, forcing you to modify it each time you need to change it's behavior slightly.

The solution is to use the Python getopt module, which works similarly to the feature available in Unix shell scripts. It also adds "long options", which the Perl getopt module provides.

For instance, the following is the beginning of a sample script that might be used to create a JMS module in a domain. Instead of hardcoding the parameters into the script, they're expected to be passed in on the command line. If any errors occur while gathering the command-line arguments, the "usage()" method is called, and the script exits.

import sys
import os
from java.lang import System

import getopt

def usage():
print "Usage:"
print "createJMSModule [-n] -u user -c credential -h host -p port -s serverName -m moduleName [-d subDeploymentName] -j jmsServerName"

opts, args = getopt.getopt(sys.argv[1:], "nu:c:h:p:s:m:d:j:",
["user=", "credential=", "host=", "port=",
"targetServerName=", "moduleName=",
"subDeploymentName=", "jmsServerName="])
except getopt.GetoptError, err:
print str(err)

reallyDoIt = true
user = ''
credential = ''
host = ''
port = ''
targetServerName = ''
moduleName = ''
subDeploymentName = 'DeployToJMSServer'
jmsServerName = ''

for opt, arg in opts:
if opt == "-n":
reallyDoIt = false
elif opt == "-u":
user = arg
elif opt == "-c":
credential = arg
elif opt == "-h":
host = arg
elif opt == "-p":
port = arg
elif opt == "-s":
targetServerName = arg
elif opt == "-m":
moduleName = arg
elif opt == "-d":
subDeploymentName = arg
elif opt == "-j":
jmsServerName = arg

if user == "":
print "Missing \"-u user\" parameter."
elif credential == "":
print "Missing \"-c credential\" parameter."
elif host == "":
print "Missing \"-h host\" parameter."
elif port == "":
print "Missing \"-p port\" parameter."
elif targetServerName == "":
print "Missing \"-s serverName\" parameter."
elif moduleName == "":
print "Missing \"-m moduleName\" parameter."
elif jmsServerName == "":
print "Missing \"-j jmsServerName\" parameter."

print "Got all the required parameters"

Calling WLST scripts from the shell requires actually calling the "wlst" application, and passing your script, and the additional command line parameters, as arguments to "wlst". For instance, this is the skeleton of a Bash script file (use Cygwin on Windows) that could be used to call this script. I assume that WEBLOGIC_HOME points to your WebLogic installation (like "c:/bea/weblogic92") and WLST_SCRIPTS_HOME points to your repository of scripts for execution.

#! /bin/bash
$WEBLOGIC_HOME/common/bin/wlst.cmd $WLST_SCRIPTS_HOME/src/ "$@"

This would produce output like this (output in versions besides 9.2.2 might vary slightly):

% ./samplegetopt -n -u weblogic -c password -h -p 8001 -s joe -m blow -j jmsserver



Your environment has been set.


Initializing WebLogic Scripting Tool (WLST) ...

Welcome to WebLogic Server Administration Scripting Shell

Type help() for help on available commands

Got all the required parameters
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