How to Handle a Variable Number of Parameters in Apache JMeter

If your request has a lot of parameters which are being passed to HTTP, creating a request to manually correlate the data will be a cumbersome process, where we can use scripting capabilities using any of the preprocessors.

I have got almost 484 parameters which have to be correlated, as shown below.

https://performanceengineeringsite.wordpress.com/2017/08/01/how-to-handle-variable-number-of-parameters-in-apache-jmeter-part-2/

Capture all the param names and param values using a regular expression extractor and dynamically send the argument with a “key,Value” pair using Sampler with the predefined variable, as shown below:

paramname = <input type=”hidden” name=”(.+?)” value=”[a-z|0-9]+”

paramvalue = value=”([a-z|0-9]+)”

The string which is enclosed in parenthesis () will get stored in a reference name.

In order to capture all the match occurrences, we will use Match, now attributed as “-1,” as below.

Steps:

1. Capture all the param names and param values parameters as above by using a regular expression extractor.

2. Based on the param count we can construct the dynamic parameters using a preprocessor.

3. Add a JSR223 Preprocessor to the HTTP request as below, and delete the parameters from the HTTP request.

The JSR223 PreProcessor allows JSR223 script code to be applied before taking a sample.

The following JSR223 variables are set up for use by the script:

• log – (Logger) – can be used to write to the log file.
• Label – the String Label.
• FileName – the script file name (if any).
• Parameters – the parameters (as a String).
• args – the parameters as a String array (split on whitespace).
• ctx – (JMeterContext) – gives access to the context.
• vars – (JMeterVariables) – gives read/write access to variables:

  vars.get(key);
  vars.put(key,val);
  vars.putObject("OBJ1",new Object());
  vars.getObject("OBJ2");

• props – (JMeterProperties – class java.util.Properties) – e.g. props.get(“START.HMS”);props.put(“PROP1″,”1234”);
• sampler – (Sampler)- gives access to the current sampler.
• OUT – System.out – e.g. OUT.println(“message”).

For details of all the methods available on each of the above variables, please check the Javadoc.

Using a sampler variable we can access the addArgument method, which passes a name and value, which can be constructed dynamically using the below code:

public void addArgument(String name,
                        String value)

//vars – (JMeterVariables) – gives read/write access to variables

//vars.get(“jmetervariable”) – gets the variable value which is in string format

int count=Integer.parseInt(vars.get(“paramname_matchNr”))

log.info “parameters count” + count

for(int i=1;i<=count;i++){

sampler.addArgument(vars.get(“paramname_” + i),vars.get(“paramvalue_” + i))
}

log.info “completed”

We can verify the request in view results tree as below.

This way we can construct a dynamic number of requests using simple variables.