How Wildfly uses the expression evaluator to evaluate attributes

In WildFly expressions are mechanism that enables you to support variables in your attributes. A typical usage is that you want the value of attribute to be resolved using System or Environment properties.

An example expression is:


This means that the value should derive from a system property named and if it is not defined use as fallback

Expression types are supported:

  • System properties, which are resolved using java.lang.System.getProperty(String key)
  • Environment properties, which are resolved using java.lang.System.getEnv(String name).
  • Security vault expressions, resolved against the security vault configured for the server or Host Controller that needs to resolve the expression.

In all cases, the syntax for the expression is


What if your expression contains itself a ${...} expression ? Then in order to avoid the expansion of the property you need to use an extra dollar sign: $${property}

If you are interested in reading just environment variables with WildFly, then check this tutorial: How to use environment variables in WildFly configuration (standalone.xml or host.xml)