public class PersonProject implements Serializable {

   @EmbeddedId
   private PersonProjectPK pk;

   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "PERSON_ID", insertable = false, updatable = false)
   private Person person;
   
   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "PROJECT_ID", insertable = false, updatable = false)
   private Project project;
   
   @OneToMany(mappedBy="parent", cascade=CascadeType.ALL, fetch=FetchType.LAZY)
   @IndexColumn(name = "ROLE_ID", base = 0)
   private List<PersonProjectRole> roles;
   
   ....
}

@Embeddable
public class PersonProjectPK implements Serializable {
   
   private Long personId;
   private Long projectId;
   ...
}
   
   
public class PersonProjectRole implements Serializable {
   
   @EmbeddedId
   private PersonProjectRolePK pk;

   @ManyToOne(fetch = FetchType.LAZY)
       @JoinColumns({
           @JoinColumn(name="PERSON_ID", insertable = false, updatable = false),
           @JoinColumn(name="PROJECT_ID", insertable = false, updatable = false)
       })
   private PersonProject parent;
   
   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "ROLE_ID", insertable = false, updatable = false)
   private Role role;
   

}

@Embeddable
public class PersonProjectRolePK implements Serializable {

   private Long personId;
   private Long projectId;
   private Long roleId;
   ...
}