How to feed an answer back into a request in Gatling - gatling

Question

I'm working in Scala with Gatling.
I need to follow a redirection found in a HTML page, sent as a response for my first request (so the automatic redirection following of Gatling doesn't do the trick).
Right now my solution looks a bit like this:
private def scn: ScenarioBuilder = {
scenario("KLS test tool")
.repeat(nb_req) {
feed(feeder)
.exec {
http("request").
httpRequest("GET", "${url}")
.check(bodyString.saveAs("body"))
}
.exec {
session => {
val responseBody = session.attributes("body").toString
val redirect = findRedirectUrlIn(responseBody)
redirect match {
case Some(url) =>
java.lang.System.setProperty("redirect_url", url)
case None =>java.lang.System.setProperty("redirect_url", "")
}
}
}
.exec {
val redirect = java.lang.System.getProperty("redirect_url")
val url = "/redirect?url=" + redirect
http("redirect").
httpRequest("GET", url)
}
}
}
However, the second exec (which is supposed to scan the HTML page to find the URL to redirect to) is being run after the third exec (which is supposed to actually visit the URL), so the getProperty gives me "null"
How could I force Gatling to run the execs in the right order?

Answer 1

I have similar task, but did in another way... What if disable redirects?
Just add disableFollowRedirect to your HttpProtocolBuilder:
val protocol = http
.baseUrl(...)
.disableFollowRedirect
Then I made request which redirected and save to redirect_url
val getUrl: HttpRequestBuilder = http("getShortUrl")
.get("${shortUrl}")
.check(
status.is(302),
header("Location").saveAs("redirect_url")
)

Answer 2

What you're doing is wrong.
First, System properties are non thread safe and global. You need a user scope, which is the Session.
Then, in your 3rd exec, your code is executed when the Simulation is instantiated as it's not in a function like the 2nd one.
.exec { session =>
val redirect = findRedirectUrlIn(session("body").as[String])
session.set("redirect_url", redirect.getOrElse(""))
}
.exec(http("redirect").get("${redirect_url}"))