All Implemented Interfaces:
Expression

public final class KeyExpression extends EncapsulatedIdentificationVariableExpression
An identification variable qualified by the KEY operator is a path expression. The KEY operator may only be applied to identification variables that correspond to map-valued associations or map-valued element collections. The type of the path expression is the type computed as the result of the operation; that is, the abstract schema type of the field that is the value of the KEY operator (the map key).

This is part of JPA 2.0.

BNF: KEY(identification_variable)
Since:
2.3
Version:
2.5