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Sunday, February 26, 2017

Test Java class with JMeter

It is quite easy to test API or Website using JMeter but you may come across situation when you have to load test java class directly. This post described how a java class can be load tested. We will write a java program and use JMeter Java Sampler to load test it. 

  • Set up a maven selenium project. If you are new to java and maven then you may like to check my java tutorials
  • Add following dependencies to your maven project - 

  • Let's write a java program to add numbers - 

public class AddNumbers {

    public int addTwoNumbers(int a,int b) {

        return a+b;



  • And a test program which we would use in JMeter later on.
  • Implement interface JavaSamplerClient or to extend AbstractSamplerClient.
  • You can leave other methods empty and would have to implement runTest and getDefaultParameters. The test class would look as -

public class AddNumberTest implements JavaSamplerClient {

    @Override public void setupTest(JavaSamplerContext javaSamplerContext) {

    public SampleResult runTest(JavaSamplerContext javaSamplerContext) {

        String var1 = javaSamplerContext.getParameter("var1");
        String var2 = javaSamplerContext.getParameter("var2");

        SampleResult result = new SampleResult();
        result.setSampleLabel("Test Sample");

        // Test Code
        AddNumbers addNumbers = new AddNumbers();
        if(addNumbers.addTwoNumbers(Integer.valueOf(var1), Integer.valueOf(var2))==2) {
        } else {

        return result;

    @Override public void teardownTest(JavaSamplerContext javaSamplerContext) {


    @Override public Arguments getDefaultParameters() {
        Arguments defaultParameters = new Arguments();
        return defaultParameters;
  • getDefaultParameters has the parameters with default values. This values would appear on Java Sampler which we
  • would see later on. runTest method uses the parameters supplied from getDefaultParameters. runTest is quiet 
  • simple. It add given numbers, if sum is equal to 2 then it is a success else failures.

  • Now package your project using mvn package and place the generated jar file in JMeter's following directory -
  • ~/apache-jmeter-3.0/lib/ext/
  • Now open JMeter and add Java sampler and select classname as AddNumberTest -

  •  Lets run the test with default variables and you will see it fails since 1+2 is not equal to 2 - 

  • Let's change default values to 1 - 

  • Let's run test again and it is green now - 

  • Now you can set up your test with required thread, duration and other parameters :)

** When you create new jar then you should restart JMeter. I did not see JMeter picking changes after placing new jar in /lib/ext/ directory and not restarting the JMeter
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