JMeter: Get list of column headers and their index - groovy

Question

I am looking for a solution to get list of column headers and their indexes.
Task: pass column headers from a CSV file and their indexes to a variable for further use in HTTP request. Idea is to create a mapping which would indicate which column to use for the given header, as following example:
name
position
company
John
manager
Alphabet
Smith
intern
JP Morgan
So the request would contain:
{"name":0},{"position":1},{"company":2}
I use multiple files where number of columns can be anything from 3 to 50 (or more), so there's no max size. I thought about following approach:
Read all headers and split by coma into a list / collection
Loop through them and use index of the list items as the index I need:
Headers: |header_1 | header_2 | ... | heade_n |
Request: {"header_1":0},{"header_2":1}...{"header_n":n-1}
Question: How to iterate through all columns while size of the file is unknown?
I found this answer where the OP has a fixed number of columns, and solution uses every value for a separate request, but I have to send only one request with the list of headers and indexes.
P.S. I am new to JMeter and Groovy, so didnt have enough time to make a full scale research. So if the answer will explain how to use pass this variable to the request would be appreciated.

Answer 1

There are no "headers" or "columns" in CSV files, there is "first line" and entries delimited by comma.
So if you file looks like:
name,position,company
John,manager,Alphabet
Smith,intern,JP Morgan
You can generate the desired request body like:
def payload = []
def firstLine = new File('test.csv').readLines().get(0)
def entries = firstLine.split(',').size() - 1
0.upto(entries, { index ->
payload.add([('header_' + (index + 1)): index])
})
vars.put('payload', new groovy.json.JsonBuilder(payload).toString())
and refer generated value as ${payload} where required
Demo:
More information:
Reading a File in Groovy
Apache Groovy - Parsing and producing JSON
Apache Groovy - Why and How You Should Use It

Answer 2

You can use Groovy to get the names of column headers.
File file = new File("<path-to-file-name>.csv")
String header_1, header_2, header_3
file.withReader {reader ->
def lstColumns = reader.readLine().split(",")
header_1 = lstColumns[0]
header_2 = lstColumns[1]
header_3 = lstColumns[2]
}

Answer 3

I need to get the value for given index so the request would be like {"name":0},{"position":1},{"company":2}, i.e. not just "header_{0}"; and with your heads-up and those links, came up with following:
def payload = []
def firstLine = new File('test.csv').readLines().get(0)
def entries = firstLine.split(',')
entries.eachWithIndex{value, index ->
log.info("'${value}': ${index}")
payload.add("{'${value}': ${index}}")
}
vars.put('payload', new groovy.json.JsonBuilder(payload).toString())
//log.info('payload : ' + new groovy.json.JsonBuilder(payload).toString())