After we upgraded our Jenkins from 1.651 to 2.7, our Groovy scripts no longer create environment variables with StringParameterValue. In this case, we use the script to get the job number for a downstream job before it's executed. This variable is then passed down in a "Trigger/call builds on other projects" step using predefined parameters.

Execute system Groovy script

import hudson.model.*

def build = Thread.currentThread().executable

def testSuite = build.buildVariableResolver.resolve("TEST_SUITE")
  
def item = hudson.model.Hudson.instance.getItem("$testSuite") 
def jobBuild = item.getLastBuild()
def nextBuildNum = jobBuild.getNumber()+1
  

def pa = new ParametersAction([
  new StringParameterValue("EXE_BUILD_NUM", "$nextBuildNum")
])
build.addAction(pa)

After the update, the variable name

"${EXE_BUILD_NUM}"

is passed in instead of the value

"46"