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Custom Java BeanShell classes and methods in JMeter

Wouldn't it be great if you were able to use the debugging capabilities of an IDE in order to write custom Java classes and methods which you could then use in a JMeter BeanShell sampler? Well, you can and this tutorial will show you how.


  • A way to create a JAR (I used NetBeans IDE)
  • Java / JDK – you can download a NetBeans + JDK combo on this page
  • JMeter

The first step is to create a class containing the custom method you’ll use in JMeter. For the purposes of this tutorial, I’ve created an example class which squares a given number. Begin by creating a new Java application project in your IDE. You should see a package and a single java file. Now you want to right-click on your project and create a second package (New -> Package), name it anything you want. From there, create a new Java file within the package. See the following example of what your project tree should look like.

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You can see we've got our project called 'MyJar', and 2 packages named bsh and test. These packages each contain a Java file. You can see ‘Whatever.java’ has a play symbol which indicates the applications point of entry; you can see the code below for both Java files, comments inline.

// Whatever.java
package bsh; // belongs to the bsh package
import test.TestClass; // importing our class (format: package.class) so we can test it
public class Whatever { // our class
public static void main(String[] args) { // this method will be run first
TestClass t = new TestClass(); // create new instance of our TestClass class
System.out.println(t.squareIt(8)); // testing our method

// TestClass.java
package test; // belongs to the test package
public class TestClass {
public TestClass() {} // empty constructor to keep things simple
public int squareIt(int i) { // our square number method
return i * i; // return the result

If you run this project, you should see the following result:

project output showing the squared result

Now that we know our program works, we need to create a JAR from it. To do so, right-click the project and select ‘Clean and Build’.

Create JAR

This will compile and create a Jar. The location of the Jar file will depend on where you saved your project, for example: C:UsersusernameDocumentsNetBeansProjectsMyJardist

The next step is to copy the JAR file into Jmeters lib/ext folder. Once that’s done we’re ready to use our custom method in JMeter. For this tutorial, I created a blank page which displays a random number. I then used JMeter's Regular Expression Extractor in order to store the number in a variable called “digit”. We will be feeding this into our custom method  to test that it works. The BeanShell sampler looks as follows:

import test.TestClass; // import our package.java file (same as import statement in IDE)
TestClass t = new TestClass(); // instantiate new TestClass
int squaredResult = t.squareIt(Integer.parseInt(vars.get("digit"))); // store returned method value in squaredResult variable. Convert param to int since squareIt expects int
log.info(squaredResult.toString());// Jmeter method to log output, convert param to string since log.info expects a string

A way we could extend the code would be to store squaredResult into a Jmeter variable using vars.put and use this elsewhere. Now that our BeanShell sampler is set up, let’s run our script. Doing so displays a page with a randomly generated number:

Randomly generated number on page

Our custom method should square this value. Checking the JMeter log file confirms our custom method works!

Showing the result of our squared number

This was a fairly simple example but showcases how it is possible to develop complex methods in an IDE, test they work before then porting them into a JMeter BeanShell sampler were they can be used.

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