java - Eclipselink insert joined object with @OneToOne -

i have 2 objects: primary key a_id, , b primary key b_id. b has foreign key a_id. while @ database level means have multiple b objects point same a, relationship 1 one b. both a_id , b_id generated sequences. have following eclipselink annotations describe relationship:

public class {     ...     @onetoone(mappedby = "a", fetch = fetchtype.lazy, cascade = cascadetype.all, targetentity = b.class)     public b getb();     ... }  public class b {     ...     @onetoone(fetch = fetchtype.lazy, targetentity = a.class)     @joincolumn(name = "a_id")     public geta();     ... } 

this doesn't work. if have object, b object set on it, , b object has same object set on it, b object not inserted, when a.getb() null. however, if change annotation on @onetomany so:

public class {     ...     @onetomany(mappedby = "a", fetch = fetchtype.lazy, cascade = cascadetype.all, targetentity = b.class)     public set<b> getb();     ... } 

with else same, inserts b, without a_id set linking object. merge logic (for both cases) boils down to:

public void merge(a obja, b objb) {     obja.setb(objb);     objb.seta(obja);     entitymanager.merge(obja); } 

i asked this question case both objects share same id. difference in question besides shared id (which leads @mapsid annotation) b object has cascade = cascadetype.all part of annotation, tried in scenario , still fails. have idea how case separate id b object work using @onetoone?