Dynamic Parameters in JMeter

Motivation

You need to send a variable number of parameters with an HTTP request i.e. the number of parameters are not known when the script is written. For example a User can register with a number of accounts , but this number varies per user. Or perhaps you want to Post process extract a number of hidden fields on the previous response and post all of them in the next Request, but you either don't know the number or there are too many fields to enter manually into the HTTPSampler.

Solution

Use a BeanShell PreProcessor to dynamically add variables to the sampler. The relevant code is sampler.addArgument(name,value)[1]

Sample

We will write a script to access a page , extract out data based on a pattern and send these as separate parameters to the next request. The script is as shown below.

We make a request to some dummy page and then we have a regex extractor to extract out multiple values. In this case the Regex extracts out all words(Match No = -1) beginning with test

Then we have a Debug Sampler to verify the regex is working, notice the results in View Results Tree Listener. The Regex has a reference variable name of inputTerms. The response of the Debug sampler is shown below

You can see from the Listeners response tab that the total number of results is 14 , available under the key inputTerms_matchNr and that each result is available as inputTerms_$resultnumber.

The matching groups which we usually do not need are available as inputTerms_$resultnumber_g$groupnumber. Armed with this information, the beanshell preprocessor script is trivial as shown below

int count = Integer.parseInt(vars.get("inputTerms_matchNr"));
for(int i=1;i<=count;i++) { //regex counts are 1 based
sampler.addArgument("hardcodedkey", vars.get("inputTerms_" + i));
}

Heres the next request to which the beanshell pre processor is attached. We have one predefined variable and the rest will be dynamically added by beanshell.

Next we check the request data we are posting using the Request tab of the View Results Tree Listener

Notice that the argument we added to the next request was sent, as were all the parameters we added dynamically. The parameter values were also encoded.
Sample Script : https://skydrive.live.com/#cid=1BD02FE33F80B8AC&id=1BD02FE33F80B8AC!268

Reference
[1] Javadocs for HTTP Sample Base

Asserting MS Office formats

As a follow up to the PDF post, you can do something similar using Apache POI

import org.apache.poi.POITextExtractor;
import org.apache.poi.extractor.ExtractorFactory;
import java.io.ByteArrayInputStream;

ByteArrayInputStream bais = new ByteArrayInputStream(in);
POITextExtractor extractor = ExtractorFactory.createExtractor(bais);
prev.setResponseData(extractor.getText());

You should be able to parse word documents and excel and ppt's using this beanshell post processor. Remember to copy the POI libraries to JMeter/lib

Future work
Look into Apache Tika for a unified interface (may need to sacrifice some functionality like the startPage endPage of PDFBox)

Asserting PDF's

A question on the JMeter mailing list regarding extracting/asserting text inside a PDF file and since I ran into this for a functional scenario , I wrote up my attempt. I use PDFBox as the library. Download the binaries and copy pdfbox-1.0.0.jar and external/fontbox-1.0.0.jar into JMeter's lib directory. We'll access the PDF at http://jakarta.apache.org/jmeter/usermanual/jmeter_distributed_testing_step_by_step.pdf and check that the PDF does contain "Distributed Testing Step-by-step" Here's the JMeter sample script So we have a transaction controller 'Check PDF' so that we only get a result item. The HTTP Request Sampler 'Request PDF' requests the PDF. The bulk of the code is in the beanshell post processor titled 'Extract Text'

import java.io.ByteArrayInputStream;
import java.io.StringWriter;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.util.PDFTextStripper;


PDDocument document = null;
StringWriter sw = new StringWriter();
try {
ByteArrayInputStream bais = new ByteArrayInputStream(data);
document = PDDocument.load(bais);
PDFTextStripper stripper = new PDFTextStripper("UTF-8");
stripper.setSortByPosition( false );
stripper.setShouldSeparateByBeads( true );
stripper.setStartPage( 1 );
stripper.setEndPage(Integer.MAX_VALUE );
stripper.writeText( document, sw );
} catch (Throwable t) {
t.printStackTrace();
sw.append("ERROR");
} finally {
sw.close();
document.close();
}
vars.put("extractedText", sw.toString());

Update - for PDFBox 2.0.26

import java.io.ByteArrayInputStream;
import java.io.StringWriter;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.text.PDFTextStripper;


PDDocument document = null;
StringWriter sw = new StringWriter();
try {
	ByteArrayInputStream bais = new ByteArrayInputStream(data);
	document = PDDocument.load(bais);
	PDFTextStripper stripper = new PDFTextStripper();		
	stripper.setSortByPosition( false );
	stripper.setShouldSeparateByBeads( true );
	stripper.setStartPage( 1 );
	stripper.setEndPage(Integer.MAX_VALUE );        
	stripper.writeText( document, sw );
} catch (Throwable t) {
                             t.printStackTrace();
	sw.append("ERROR");
} finally {
	sw.close();
	document.close();
}
vars.put("extractedText", sw.toString());

All this does is use the PDFBox API to extract text from the PDF (bytes are present in the data object) and write it to a variable in JMeter , extractedText. The next sampler is a Java Sampler which sets the ResultData to ${extracted text}. This will echo back the contents of this variable as the response of the sampler. Once this is done , you can use a normal response assertion, regex extractor or whatever else you need to process the text Update: as mentioned by Milamber in the comments , you can instead have the last line of the beanshell as

prev.setResponseData(sw.toString());

This will set the response of the HTTPSampler to be the text value and allow you to directly specify the assertion (and you can also eliminate the transaction controller). Update : if you are interested in MS office formats then follow the steps in this post, just change the BeanShell post processor to that mentioned in Asserting MS Office Formats Future work a. make a custom PDF(or any format sampler) with the options that are hardcoded (e.g. startPage or endPage) b. experiment with ways to use less memory. Typically should extract and write to file and use that.