title: Hibernate- One to Many Mapping - save relation mapping but not the nested Entity
body: <p>I have Entity A(Role) having OneToMany relationship to Entity B(Functions), when I am trying to save A, when I run it first time everything works well, next time when I want to add new role with some of functions, I get error as UNIQUE constraint as there are already records in Functions entity. </p>
  
  <p>How can I save just mapping between A &amp; B if records are already available in B.</p>