Return Types

DomEL expressions are used in different contexts for different purposes. The expected return type depends on where the expression appears:

Appears In

Expected Return Type


Join expression


Within a join expression, the on clause contains a comparison of fields from each table that has a boolean result. The on clause may also contain other DomEL expressions logically associated with and or or to create a complex join condition.

Calculated field

any type

The expression must evaluate to a type that is compatible with the SQL type declared in the Domain Designer or in the design file. For example, if the declared type is java.lang.Float, the expression must compute a decimal value.



Filters must be true or false overall. When there are several conditions, they must be logically associated with and or or (currently, only and is supported in the Domain Designer).