Jmeter -- how to combine variable name & counter() - variables

Question

I've got the following problem:
I do gather that ProductId variable is assigned with the first value and then only that value is used when I refer to ${productId}.
I was trying to apply ${__counter()} to reference name in RegexExtractor,
but then BeanShellAssertion fails to set the property.
How should I properly work this around?

Answer 1

You can use __V() function in order to combine 2 variables.
I.e. if you have 2 variables like:
productId
counter
And would like to evaluate i.e. ${productId_1}, ${productId_2}, etc.
It should be as simple as:
${__V(productId${counter})}
Same approach applies to __counter() function:
${__V(productId_${__counter(,)})}
Demo:
See How to Use JMeter Functions posts series for comprehensive information on above and other functions

Answer 2

ProdGroup
please store the product Id property as prod_id_1, prod_id_2,...prod_id_n or according to you convenience
How to to that ?
in post processor "Parameters" section use ${__counter(FALSE,)} and in the script part try getting that String counter = arg[0] and convert that to integer and store it to a script variable by default arg[0] value is String
int c= arg[0] as Integer //this is groovystyle check in your way to convert as int
now props.put("prod_id_"+c,"extractedfrom_response")
BID:
In you Bid group add a user defined variable section add the variable
"prod_id" and value is empty
Define a counter start with the same counter 1 and give counter reference name [if your counter value in prod group was 0 then here also it must start with zero]
script sampler convert all the props to the variables
Enumeration e = props.propertyNames();
while (e.hasMoreElements()) {
String propertyName = e.nextElement().toString();
if (propertyName.startsWith("prod_id_")) {
vars.put(propertyName, props.getProperty(propertyName));
}
}
With this you have converted properties to variables named prod_id_1 ...to ... prod_id_n
In http sampler user reference as ${__V(prod_id_${counterreference in step 2})} will do your job
For each thread the counter will increment by default
user ${__threadNum} or ${counter reference name} in sampler labels for debugging.
Hope this helps. Please let us know if still problem is there.