JPA Method
in javax.persistence.Subgraph

Subgraph<X> addKeySubgraph(
  String attributeName, 
  Class<X> type
)


Add a node to the graph that corresponds to a map key that is a managed type with inheritance. This allows for construction of multi-node entity graphs that include related managed types. Subclass subgraphs will include the specified attributes of superclass subgraphs
Parameters:
attributeName - name of the attribute
type - entity subclass
Return:
subgraph for the attribute
Throws:
IllegalArgumentException - if the attribute is not an attribute of this entity.
IllegalArgumentException - if the attribute's target type is not a managed type
IllegalStateException - if this EntityGraph has been statically defined
Since:
JPA 2.1