Expressions
ATB supports Groovy expressions for generating dynamic values at run time — a fresh UUID, a timestamp, a random string, or the result of a calculation. The syntax is ${= the expression }, where the leading = is what sets an expression apart from a property reference (${ ... }). Examples:
${= UUID.randomUUID() }
${= RandomStringUtils.randomAlphanumeric(10) }
${= ThreadLocalRandom.current().nextInt(0, 100) }
${= new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS").format(new Date()) }
${= (5 + 2) * 8 / 2 % 5 + 0.5 }You can embed a Groovy expression directly in a request, or inside a property’s value. For example:

When the request or test case runs, each expression is evaluated and its result is substituted in place as text.
Default Imports
Section titled “Default Imports”The following packages and classes are imported by default whenever a Groovy expression is evaluated, so you can use their shorthand names instead of fully qualified names.
java.lang.*java.util.*java.io.*java.net.*groovy.lang.*groovy.util.*java.math.BigIntegerjava.math.BigDecimalorg.apache.commons.lang3.RandomStringUtilsjava.util.concurrent.ThreadLocalRandomjava.text.SimpleDateFormat