| Expressions are in the form of ${key:defaultValue}. If the key is prefixed withsys.a system property is
used. If the key is prefixed withenv.an environment variable is used. In all other cases the properties are resolved
from theorg.jboss.logging.tools.expressionPropertiespath. If the key is not found in the properties the default
value will be used. | 
| Expressions are processed at compile time. The values will be hard-coded in the generated source files. |