CollectionTable.joinColumns - JPA annotation element

Annotation Element
JoinColumn[] joinColumns

(Optional) The foreign key columns of the collection table which reference the primary table of the entity. The default only applies if a single join column is used. The default is the same as for JoinColumn (i.e., the concatenation of the following: the name of the entity; "_"; the name of the referenced primary key column.) However, if there is more than one join column, a JoinColumn annotation must be specified for each join column using the JoinColumns annotation. In this case, both the name and the referencedColumnName elements must be specified in each such JoinColumn annotation.
Default value:
JPA 2.0

This documentation page is derived (with some adjustments) from the open source JPA 2 RI (EclipseLink)
and is available under the terms of the Eclipse Public License, v. 1.0 and Eclipse Distribution License, v. 1.0.
Object Relational Mapping (ORM) JPA 2 providers include Hibernate, EclipseLink, TopLink, OpenJPA and DataNucleus.
ObjectDB is not an ORM JPA implementation but an Object Database for Java with built in JPA 2 support.