index.md

title	seotitle	description	lead	date	lastmod
Functions	Gatling session scripting reference - functions	How to use functions to compute dynamic parameters based on Session data using all the power of programing language of choice (Java, Kotlin or Scala)	Use functions to programmatically generate dynamic parameters	2021-04-20 18:30:56 +0200	2022-12-14 21:30:56 +0200

Sometimes, you might want to dynamic parameters that are too complex to compute for Gatling EL. Most Gatling DSL methods can also be passed a function to compute your parameter value programmatically.

{{< alert warning >}} Those functions are executed in Gatling's shared threads, so you must absolutely avoid performing long blocking operations in there, such as remote API calls. {{< /alert >}}

{{< alert warning >}} Remember that the [Gatling DSL components are merely definitions]({{< ref "/reference/glossary#dsl" >}}). They only are effective when chained with other DSL components and ultimately passed to the setUp. In particular, they have no effect when used inside functions. {{< /alert >}}

Syntax

Those functions always take a Session parameter, so you can extract previously stored data.

The generic signature of these functions is:

• In Java and Kotlin: Session -> T
• In Scala: Expression[T] is an alias for Session => Validation[T]. Values can implicitly lifted in Validation.

{{< include-code "function" java kt scala >}}

{{< alert warning >}} (Scala Only): For more information about Validation, please check out the [Validation reference]({{< ref "validation" >}}). {{< /alert >}}