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Jmeter generates json request payload dynamically

I have a Jmeter test plan where I want my HttpSampler to send a post request.

The request body should contain Json like this:

{
  "productIds" : [
    "p1",
    "p2",
    ...
  ]
}

I have a random variable generator that returns a well-formed product with every call. What I would like to do is generate the payload by populating the productIds with a random pid taken from the generator directly in the request body. Something like (assume *** is a scripting escape):

{
  "productIds" : [
     ***
       for i in (1, $productsCount) {
         write("\"$randomPid\"\n")
       }
     ***
  ]
}

Is it possible? If so, how? If not, how do you approach the problem?

Thank!

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1 answer


  • Add Beanshell PreProcessor as a child of the request you want to parameterize

  • Place the following code in the PreProcessor "Script" area:

    StringBuilder result = new StringBuilder();
String newline = System.getProperty("line.separator");
int max = Integer.parseInt(Parameters);
Random random = new Random();

result.append("{");
result.append("\"productIds\" : [");
result.append(newline);
for (int i = 1; i < max; i++) {
    result.append("\"").append(random.nextInt()).append("\",");
    result.append(newline);
}
result.append("]");
result.append(newline);
result.append("}");

vars.put("json", result.toString());
  • Place the value $ {productsCount} in the "Parameters" line
  • Refer to the resulting payload as ${json}

    where required


See How to Use BeanShell: A Favorite Built-in JMeter Component for more information on Apache JMeter Beanshell Scripting.

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