Cannot extract variable with RegEx from a Mail Reader in jMeter - regex

Question

I have the following setup:
Thread
Mail Reader Sampler
Regular Expression Extractor
Viewer
HTTP Sampler
Viewer
What I'm trying to do is retrieve an email, extract a value from it and then pass it as a variable in the next request.
The problem is that the retrieved email comes in the following format:
Mail Reader Sampler
Message 1
Part 0
Part 1
The info that I'm aiming for is located in "Part 1". And this is causing my problem...jMeter can not extract it because it is a sub-sub-sample.
If the desired variable was located in the "Message 1" part, then jMeter is extracting the value without any problems and is then passing it to the next request.
My RegEx setting is "Apply to main sample and sub-samples", so theoretically, this shouldn't be a problem..but apparently is.
How can I get jMeter to extract the wanted value when the retrieved email comes in multiple sub-parts?

Answer 1

Unfortunately Regular Expression Extractor processes only direct sub-samples so in case of multipart email messages you will be able to extract only This is a multipart message in MIME format. line which is not very helpful.
I would recommend adding a Beanshell PostProcessor as a child of the Mail Reader Sampler but before the Regular Expression Extractor and use the following code:
import org.apache.jmeter.samplers.SampleResult;
StringBuilder response = new StringBuilder();
for (SampleResult message : prev.getSubResults()) {
response.append(message.getResponseDataAsString());
for (SampleResult part : message.getSubResults()) {
response.append(part.getResponseDataAsString());
}
}
prev.setResponseData(response.toString(), "UTF-8");
The above code will traverse down all the messages and their parts, extract response data and substitute Mail Reader Sampler's default response data X messages found with the actual contents of these message(s) so you will be able to use the Regular Expression Extractor for correlation.
See How to Use BeanShell: JMeter's Favorite Built-in Component article for comprehensive information on using scripting in JMeter tests.