Has one used XSLT BSF preprocessor in Jmeter? - jmeter

Question

Has anyone used BSF pre-processor in JMeter? What is the difference in the working between pre-processor and sampler? What is the difference between Beanshell processor and BSF processor?
My requirement is that I have a sample XML that I need to use to generate as many XMLs for the HTTP request I am going to load test. For this, I was planning to use BSF pre-processor to create an XML string using XSLT transformation of the template XML, within a loop (as many number of requests I want to generate). I would then use the string variable pointing to the created XML in each iteration of the loop for the corresponding HTTP request. So the questions in earlier paragraph are to validate this approach.
IF this approach is OK, I could not figure out how to use XSLT BSF pre-processor? I wrote as well as tried specifying the XSL in the script section, but could not figure out how to pass input XML? What does the String parameter input mean? It was throwing a NullPointerException for that parameter? IS that the way to specify input XML? If yes, please give an example.
Anybody who has worked in this, please share whatever inputs you can.
Thanks,
Paddy

Answer 1

Kindly find answers below:
What is the difference in the working between pre-processor and sampler
PreProcessor is executed before sampler. Pre- and PostProcessor execution time is not recorded so they're handy to use i.e. to prepare test data or do something with it after sampler end.
What is the difference between Beanshell processor and BSF processor?
Beanshell test elements support only Beanshell language while BSF supports JavaScript, jexl, jacl, jml, etc.
For lightweight scripting it's better to use Beanshell as engine initialization time is less, however if your script is doing "heavy" operations it's better to use JSR223 Sampler and Groovy as a language. See Beanshell vs JSR223 vs Java JMeter Scripting: The Performance-Off You've Been Waiting For! for scripting extension engines benchmark and details on how to install Groovy language support.
how to pass input XML
It can be done via Parameters section which accepts any string.
If you have your XML file as JMeter variable you can access it from the script as:
String xml = vars.get("myVar");
UPDATE: Example PreProcessor Code
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import java.io.File;
TransformerFactory factory = TransformerFactory.newInstance();
Source xslt = new StreamSource(new File("/path/to/your/xsl/file.xsl"));
Transformer transformer = factory.newTransformer(xslt);
Source xml = new StreamSource(new File("/path/to/your/source/xml/file.xml"));
transformer.transform(xml, new StreamResult(new File("/path/to/result/xml_or_html/file")));