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Sunday, March 20, 2011

WLST Tricks & Tips

Here I prepared few of the "Tips" and some commonly useful "Tricks" for developing the huge WLST scripts. These are all the learnings which I have came across in my daily working experiments with Programming Python commands for WLST scripts. These WLST commands can be applicable from WebLogic 9.x to WebLogic 10.3.6 and latest trending WebLogic 12c as well.
  1. Tip 1: Know about Where are you in WLST?

  2. On some situations you might need a clarity about which WebLogic version you are using. WebLogic 11g (10.3) has different subsequent versions 10.3.1,10.3.2,10.3.3 and 10.3.4, for all these the directory structure is ~/Oracle/Middleware/wlserver_10.3 which does not tells you about sub versions. Here WLST  is having a solution for this problem,

    You can find the current WebLogic version to which WLST is connected.

    wls:/offline> print version
    WebLogic Server  Fri Apr 9 00:05:28 PDT 2010 1321401

    How do you know that the WLST Shell running on which JVM version? The simple solution is you this following Python command that will gives you:

    wls:/offline> sys.platform

  3. Tip 2. How to know Jython version is used by WLST?

  4. To get the Jython version you can use sys.version_info method that will returns. or you can use sys.version exact version.

    wls:/offline> import sys
    wls:/offline> sys.version_info
    (2, 2, 1, 'final', 0)

    Tip 3. Introspection in WLST

    You might understand that using WLST provided help() sometimes you cannot reach your desired level of script code. Some thing that won't be documented but you might need it to develop the prototype in your WLST script. Often I found this could be a need, most helpful way to reach depth of WLST classes, modules, functions. Best way is we need to use Python introspection methods. It is a wonderful way to resolve your coding clues to use best performing script as outcome.

    In some of the situations, I felt using Jython (Java method) is lengthy than using Python. When Python giving you desired outcome in two lines of code why do you choose Java imports and classes and code become 6-10 lines.

    You might be confused sometimes, brain storm about something why a MBean not working or giving the value of an attribute etc. In your mind there could be a question "what is this actually??" Best solution for this is using Python introspection built-in methods.

    dir([WLST/Python Object])
    If your WLST MBean or module or a function has documented then you use the following to get that:

    In Jython there could be classes or interfaces

    Tip 4. Naming Rules for WLST

    WLST script can have names are case sensitive and cannot start with a number.  They can contain letters, numbers, and underscore symbols. Let us see few examples here:
     state  State  _state  _2_state_  state_2  StatE

    Most of us face an issue what name makes sense for a variable, module or classwhile writing the WLST scripts. Just like Java Language you can follow specific naming rules, we can also find keyword list available in WLST with the following commands

    wls:/offline> import keyword
    wls:/offline> keyword.kwlist
    ['and', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while', 'yield']

    Modules, packages: use lowercase
    Classes: use Capitalized first letters in the Words also follow for exceptions that you create
    Methods, attributes: use lowercase_words
    Local variables: use alphanumeric i, j, sum, x0, etc.
    Globals: use alphanumeric long_descriptive_names

    wls:/offline> sys.modules
    {'': , ...'sys': sys module, '': }

    Introspection reveals useful information about your program's objects

    Tip 4 Write a readable script

    While writing a script think about the human readers, Question yourself can you still read your own code ???
    next month?
    next year?
    • Be consistent (but not too consistent!)
    • Use white-space judiciously
    • Write appropriate comments
    • Write helpful doc strings -- not stories or novels
    • Confirm to the existing style even if it’s not your favorite style!
    • local consistency overrides global
    • Update the comments!!and the doc strings!!!

    """Brief one-line description.
    Longer description, documenting
    argument values, defaults,
    return values, and exceptions.

    When to use classes in WLST? (...and when not!)
    If your script objective is going to have multiple object creation then go for Object-Orientation.

      • You could choose class members or attribute  at the first time
      • name clashes between attribute

    Tip 5 Convene print statement with str()

Most of us from Java/JEE development background common attitude is that using the + operator overloading for strings. Sometimes your WLST script might need to have a print statement, that could include values from a variable or some mathematical expression that might be int type or some other object type. Then such cases, better to use that variable type must be converted to string type by using Python built-in function str() as shown :

print 'Heap Size' + str(totalHeap)

Tip 6: Create single properties file

Every Middleware admin whoever uses this WLST in their environment builds, they must create/use a single properties file where you can have:

  1. Domain properties - username, password, admin url, cluster list
  2. Database configuration properties
  3. JMS configuration properties
  4. WorkManager properties
  5. Monitoring Threshold properties

Tip 7: Using time in WLST

In my daily news updates from social medias I found in in the Python community doing excellent there is lots of news about the changes happening with Python programming. One of the blog found very nice examples with date and time functions in Python this can be applicable for our WLST too.

Setting UTC time zone in Python

WLST Tricks

We have come across many situations where it is simple trick works faster to work with WLST scripting. some of them collected here and future also we will update this WLST tricks

Trick 1. Multiple Assignment

In WLST you can assign multiple variables with corresponding multiple values at the same statement or command line.

wls:/offline> cl, ms = ['appclstr','webclstr'], ['app01','app02','web01','web02']
wls:/offline> cl
['appclstr', 'webclstr']
wls:/offline> ms
['app01', 'app02', 'web01', 'web02']

Trick 2. Connect admin without Credentials

When you use storeUserConfig() command for your WebLogic domain environment, the trick here is when you don't specifying any arguments such as user security file, key file paths. WebLogic system automatically generates the following two files:

For example, Let us assume your user name is 'padmin' then storeUserConfig() command will generates two files as:

Once you got this auto-generated files in you home ($HOME in Unix) directory, WLST Shell automatically detects its existance from this location. You don't need to give the userConfig, Key file paths while connecting. Simply you can connect by giving the adminurl as url value.

wls:/offline> connect(url='t3://')
Connecting to t3:// with userid weblogic ...
Successfully connected to Admin Server 'wadmn' that belongs to domain 'mydomain'.

Warning: An insecure protocol was used to connect to the
server. To ensure on-the-wire security, the SSL port or
Admin port should be used instead.

Trick 3: Command Trials

The interactive mode is great for getting instant feedback on the behavior of each WLST command. Having the whole startup, connection, session-init is time-consuming and the interactive mode of WLST avoids this.

First time if you are making a script better idea is have duplicate windows of the host. In one window you can edit and save according to your required changes, on the other hand you can execute the file with execfile('').

Trick 4: Using loadProperties

One of my blog follower Raghu asked me how to use properties in the WLST script. Though I had used different types of properties from properties file, but his requirement is something different he want to reuse the WLST script only by changing the properties file.


Here is the WLST script snippet that uses above defined properties using loadProperties() built-in function call
print serverlist[1]

for i in serverlist:
    print i

Remember that properties are just like Java language properties or C/C++ define constants, which holds name, and corresponding the string values. So when you store portno in properties file better convert using int().
Hope this is useful for your reusable scripts.

Trick 5: How to debug WLST script?

The best way to identify the WLST script bugs using dumpStack(). This works only when you are running interactive mode. If you found a script (such as my blog) or from somewhere after you update all properties you wish to test and it doesn't works! then you wish to debug it.

1. Using simple print variable values
2. Using Python exception values
3. Double check indentations
4. Casting values (converting values str to int or str to bool)

Some of the cases you need to understand that casting fails the values are not allowed to change because WLST variables are created in Runtime. The datatypes are strong type like Java and C++ languages and dynamic type while running it will be assigned to a datatype.

You can enable debug flag at the time of invocation of WLST shell.

java -Dpython.verbose=debug weblogic.WLST

Also you have one more option using debug("true") or set('DebugEnabled', 'true') in the starting of WLST script that will force debug output

If you are using OEPE (Eclipse for developing WLST) then you have much scope to debug every variable content. Right click on the WLST script select 'Debug As', choose 'WLST run' from the list Menu. Please check the screenshot that give you more clear idea on this Oracle link.

Trick Cancel the Edit in WLST

Today while working on WLST in interactive mode to fix the JMS configuration issue, sometime you start editing the configuration you might need to undo the changes you did on the edit tree. This is possible using cancelEdit() give the answer y to confirm when it prompts you. Else you can use cancelEdit('y') as a trick.

Trick 6: Suppress Junk Output in WLST

There is junk when you capture the list from ls(returnMap='true') command execution.
If you are running WLST in *nix based environment you can use /dev/null path for suppressing the junk outputs as shown below redirect command.


Trick 7: Resolve indentation/dedent issue with vi setting

WLST Code copied from NotePad++ to vi editor tabspace issue
when you write few lines in the notepad++ it takes 4 spaces as tabspace, but in the vi editor it is 8 it mismatches and cannot fit into the block. So when run the script it throws 'dedent' issue. To resolve this in vi editor you can set the tabspace=4

: set tabspace=4

Keep writing your valuable comments and great suggestions to improve this blog tutorial ...

  1. 1. Dive into Python
  2. Python Library link


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