JMETER | How To Write Data From Response To A CSV File

Problem Statement:

As an Automation Tester,
I want to Save Response Data to file
And I want to extract some portion of response 
So that I can generate .csv file which can be utilized further

• If we understood the problem statement better then basically, we have TWO global objectives which we are trying to solve.

1. Save response to file (Can Achieve by using “Save Responses to a file” listener)
2. Extract few portion of response and save to .csv file. (Little complex and can’t be achieved by in-built component of Jmeter.)

Why we need Response to store?

• It’s requirement of test. We can use this data for subsequent analysis, importing to a database, and more. Responses are used to debug further environment.
• Handle too large Response — We will not be able to see a response in the View Results Tree if the size of the response is more than 200K. There are a couple of ways to solve this problem and one of them is saving the response to a file.

Solution:

API under Jmeter Test

API Details:
-----------------
End-point: 
URL
Input Param:
name = Ahmed

Let’s see step-by-step how problem statement can be achieved -

1. Add basic elements to the Test plan.

Jmeter Structure

* Test plan -> Add -> Thread (Users) -> Thread Group
* Thread Group -> Add -> 
- Config Element -> User Defined Variables
- Sampler -> HTTP Request
- Listener -> Save Responses to a file
- Listener -> View Results Tree

• Let’s add user defined variable called name which we would like to pass to next request. (Name=Ahmed)

User Defined Variables

• Added HTTP request to get name & pass user defined variable. ${Name}

HTTP Request (GetByName)

2. We are just about done! Run the script.

• As we can see, each request has a response in the View Results Tree. This is very comfortable for debugging.

Response in View Tree

• Since we have added “Save response to file” as listener, there will be separate file created under <JMETER_HOME>/Bin folder.

Where we have reached so far?

We have achieved first goal which is to save response to file. What is Next -

A) Need to extract details from response and
B) Only extracted details should be saved to .csv file for further use.

A) Need to extract details from response:

• Add below elements to Existing Test Plan

* Thread Group -> Add -> Sampler -> Debug Sampler
* HTTP Request -> Add -> Post Processors -> XPath2 Extractor

• XPath Extractor to get all entities who name is “Ahmed”.

XPath2 Extractor

Where-
* XPath query : //name
* Match No. should be -1 ( extract all results, they will be named as <variable name>_N (where N goes from 1 to Number of results))

* We are just about done! Run the script.

• The Debug Sampler generates a sample containing the values of all JMeter variables and/or properties.
• The values can be seen in the View Results Tree Listener Response Data pane.
• We can observed that all matching names are extracted and assigned to unique variable by default.

Debug Sampler Response in View Tree

B) Only extracted details should be saved to csv file:

• Add below elements to Existing Test Plan

* HTTP Request -> Add -> Post Processors -> JSR223 PostProcessor

• Now, it’s time to write JAVA code inside JSR223 PostProcessor to get all extracted variables and write into the csv file.

import org.apache.commons.io.FileUtils
import java.text.SimpleDateFormat;
// Get total number of matches. (Returns string)
def resultCount = vars.get("ExtractedName_matchNr")
log.warn 'Output to jmeter console' +  resultCount
// Generate timestamp to create uniue file name.
String fileSuffix = new SimpleDateFormat("ddMMyyyyHHmm").format(new Date())
// Create file Object
f = new File("results_"+fileSuffix+".csv")
for (int i=1; i<=resultCount.toInteger(); i++)
{
  // Get each matching result one by one.
  records = vars.get("ExtractedName_"+i)
// Write result to csv file.
  FileUtils.writeStringToFile(f,records + System.getProperty("line.separator"),true)
}

JSR223 PostProcessor-To extracted result to csv file

We are just about done! Run the script.

• There will be separate file created under <JMETER_HOME>/Bin folder. (EX: results_xxxxxxxxxxxx.csv)

Conclusion:

There is no direct way to save extracted response to the CSV file. Needed processors like JSR223 PostProcessor in order to achieve our objective.

Note: Probably, Given problem statement can be addressed by different ways in Jmeter which I have not explored yet. Source code(LearnCSVDataExport.jmx) is available on GitHub.

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