Enterprise Java

Apache JMeter: Load Test Whatever You Want

This is the second post about load testing with Apache JMeter, read the first post here: A step by step tutorial about load testing relational databases.
JMeter has lots of Samplers. If you need a sampler that is not provided by JMeter you can write your custom sampler. (custom samplers are called “Java Request” in JMeter terminology)

This post will show you, step by step, how to write a JMeter Java Request.

Step 1: Preparing the development environment

Add these two jar files to the java classpath.

  1. $JMETER_HOME/lib/ext/ApacheJMeter_core.jar
  2. $JMETER_HOME/lib/ext/ApacheJMeter_java.jar

(If you are using Eclipse, add these files as external jar files to the java build path.)

Step 2: Extending AbstractJavaSamplerClient

After setting up the classpath, create a custom sampler by extending AbstractJavaSamplerClient and override the following methods.

public Arguments getDefaultParameters() {...}
public void setupTest(JavaSamplerContext context) {...}
public void teardownTest(JavaSamplerContext context) {...}
public SampleResult runTest(JavaSamplerContext context) {...}

Implement getDefaultParameters if you want initial values for test paramters. JMeter will display the parameters in its Java Request configuration GUI. (See the contents of the red rectangle in the picture below.) Here’s an example implementation:

public Arguments getDefaultParameters() {
    Arguments defaultParameters = new Arguments();
    defaultParameters.addArgument("memcached_servers", "localhost:11211");
    defaultParameters.addArgument("username", "testuser");
    defaultParameters.addArgument("password", "testpasswd");
    return defaultParameters;

This is where you read test parameters and initialize your test client. JMeter calls this method only once for each test thread.

Clean up the mess.

Write your test logic in this method. JMeter will call runTest method for every execution of test threads. Here is a typical runTest implementation:

public SampleResult runTest(JavaSamplerContext context) {
    SampleResult result = new SampleResult();
    boolean success = true;
    // Write your test code here.
    return result;

The time elapsed betweed result.sampleStart() and result.sampleEnd() is used to calculate average response time of the application under test.

Step 3: Deploy your custom sampler

When you are done create a jar file (containing your custom sampler) in the $JMETER_HOME/lib/ext/ directory. JMeter will display your java request in the java request configuration page.

You can see the results of your test by adding listeners to your test plan. “A step by step tutorial about load testing relational databases” post shows how to add listeners to test plans.

Reference: Load Test Whatever You Want With Apache JMeter from our JCG partner Ilkin Ulas at the All your base are belong to us blog.

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Nikhil Ninawe
Nikhil Ninawe
11 years ago

perfect article..done my job..

Imen CHOk
Imen CHOk
9 years ago

Great , ii’s been very useful article and it solve my problem thanks a lot :D

Dmitri T
Dmitri T
9 years ago

Thanks for great post. There is a way to execute custom Java code right from JMeter test using Beanshell Sampler. It won’t require custom coding, packaging, deploying, etc. however full access to Java and JMeter API will be provided. See How to use BeanShell: JMeter’s favorite built-in component guide for more details

Tejas H
Tejas H
9 years ago

Thanks for a great post. When you define parameters in getDefaultParameters method how do you get the parameter’s value in runTest? How do I get the username and password passed in my code?

9 years ago

Thanks for this post. How can I generate result file (jtl) from java code?

Carlos Guizar
Carlos Guizar
1 year ago

I’ve been struggling creating a Java Sampler that calls Spring boot libraries , the problem I see is that the spring Objs are never booted. even though the dependencies dont seem to be a problem any more, Im wondering if I should persist pursuing this kind of calls.

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