Dmitri Tikhanski

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How to Use BeanShell: JMeter's Favorite Built-in Component

Sep. 27th, 2015
BeanShell is one of the most advanced JMeter built-in components. It supports Java syntax and extends it with scripting features like loose types, commands, and method closures. If your test case is uncommon and implementation via embedded JMeter components becomes tricky or even impossible, BeanShell can be an excellent option to achieve your objectives.

BeanShell entities in JMeter have access to both internal JMeter APIs and any external classes that are loaded into the JMeter classpath (be sure to drop necessary jars into /lib/ext folder of your JMeter installation and place all necessary “import” statements at the top of your BeanShell scripts).

JMeter provides the following BeanShell-enabled components:

 

  • Beanshell Sampler – A standalone sampler
  • Beanshell PreProcessor – A pre-processor to another sampler that is executed before the sampler and can be used for prerequisite setup (i.e. to generate some input). 
  • Beanshell PostProcessor –  A post-processor that is executed after the sampler and can be used for recovery or clean-up.
  • Beanshell Assertion – An advanced assertion with full access to JMeter API. Java conditional logic can be used to set the assertion result.
  • __Beanshell Function – A JMeter Function that allows execution of custom BeanShell code during a sampler run.

 

BASIC EXAMPLES

Changing JMeter Variables on the Fly

Assume you have a user-defined variable called "continue" with the value of "true" somewhere in the While loop. You can set it to "false" with this simple command:
Changing JMeter variables on the fly-Beanshell, Jmeter, BlazeMeter
 

Convert JMeter Variable to a JMeter Property

Given a variable "some_variable" you must cast JMeter Property with the same name to use, (such as in another thread group).
Convert Jmeter variable to a Jmeter property - Using Beanshell, BlazeMeter, JMeter
 

ADVANCED EXAMPLES

Passing Cookies between Thread Groups

Assuming the HTTP Cookie Manager is enabled, the following code can convert JMeter cookies into JMeter properties.
 
Convert JMeter Cookies into JMeter Properties
 
 
After all cookie information is stored as a JMeter property, you can reconstruct cookies in another thread group.
Cookie info stored as JMeter Properties -BlazeMeter, JMeter, Beanshell
 

Stopping the Test in Case of Failure

Imagine you have a 48-hour SOAK test scheduled to run over the weekend that explicitly depends on a CSV data set config element that requires source CSV files to be present. You tested it with one user and one loop on your developer machine, and it worked fine. However, when you upload it to your production environment and run headless, JMeter fails to locate the CSV file and all 48 hours are wasted. To avoid this situation, use the following check in the very first BeanShell Sampler:
 
File mycsvfile Beanshell check
 

All of the Above + BlazeMeter

This example demonstrates a simple BeanShell use case with BlazeMeter under the following TestPlan structure:
  • Thread Group (1 user, 1 second ramp-up, forever)
  • While Controller with empty condition  (forever)
    • Counter (start – 1, increment  – 1, reference name – counter)
    • HTTP request (server name – example.com)
      • BeanShell Post Processor 
The BeanShell post-processor tests if the HTTP sampler response contains the example domain. If it doesn’t, the test will fail and stop immediately. If it does, the test will stop after the third iteration. In both cases, something is appended to the jmeter.log.  
 
Benashell Post Processor
Beanshell Pre Processor
 
 
Test Report Beanshell on BlazeMeter
 
                                                                                                                                                 

JMETER PRE-DEFINED BEANSHELL VARIABLES

The next section contains the most important and most frequently used JMeter API classes exposed to BeanShell components. If you look at the bottom of BeanShell sampler component, you’ll see following:

“The following variables are defined for the script:
SampleResult, ResponseCode, ResponseMessage, IsSuccess, Label, FileName, ctx, vars, props, log”
 

SampleResult

 
SampleResult maps to the JMeter class org.apache.jmeter.samplers.SampleResult. All fields and methods outlined in the javadoc can be accessed and invoked.  Here is a sample use-case:
samples result beanshell
 

ResponseCode

 
ResponseCode is a java.lang.String that stands for sampler response code. Here is a sample use-case:
 
responsecode beanshell
 

ResponseMessage

 
ResponseMessage is a java.lang.String that represents a response message. The sample use case is the same as the one for the ResponseCode.
 

IsSuccess

 
IsSuccess is a java.lang.Boolean that reflects whether sampler succeeded. If it’s set to true, sampler is considered “passed.” Otherwise, it will be marked as “failed.”
IsSuccess
 

Label

 
Label is java.lang.String that represents sampler label. It can be get or set as a usual String and will be listed in the test results as a sampler label. 
 

FileName

 
FileName is a java.lang.String that contains a BeanShell script file name (what is entered in “Script file” stanza of the BeanShell Sampler). 
 

ctx

 
ctx is the most powerful variable exposed to BeanShell. It represents the  org.apache.jmeter.threads.JMeterContext class, which is virtually JMeter itself. It provides read/write access to the underlying JMeter engine, samplers, and their results as well as variables/properties. 
 

vars

 
vars (JMeter variables) is the most frequently used component. It’s an instance of the org.apache.jmeter.threads.JMeterVariables class and provides read/write access to current variables, is capable of enumerating/changing existing variables, creating new ones, and obtaining nested properties.  All JMeter variables are Java strings. If you need to put something else to a JMeter variable, you’ll need to cast it to string first. The following code snippet demonstrates how to save previous sampler response data into a JMeter variable.
btx sampler data beanshell
 

props

 
Basically, this is the same as “vars,” but it exposes JMeter properties instead. See JavaDoc on java.util.Properties and JMeter documentation on JMeter properties for more information. The primary distinction between props and vars is that props have a “global” scope, whereas the scope of “vars” is limited to the current thread group. 
 

log

 
log represents the org.apache.log.Logger class and can be used to append a message into jmeter.log file. See JavaDoc on logger for more details. The following is the sample use case:
 
logs using Beanshell with JMeter and BlazeMeter
 

DEBUGGING OF BEANSHELL SCRIPTS

As BeanShell is executed within the Rhino engine, there is no other option to see what’s wrong, apart from inspecting jmeter.log file for something like:
 
Error invoking bsh method 
 
and using System.out.println(“something”) or log.info(“something”) to determine where the script fails.
 

LEARN MORE

If you are new to JMeter, and you’d like to learn more, please sign up for our free online JMeter training course.
 
For more experienced JMeter users, you'll want to view the on-demand webcast, How to Create Advanced Load Testing Scenarios with JMeter.
 
Be sure to read through all our JMeter list of resources
Dmitri Tikhanski
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Dmitri Tikhanski is a Contributing Writer to the BlazeMeter
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