(parent and child one to one relation)

Parent pa=new Parent();
pa.setName("laojiang");
Child ca=new Child();
ca.setName("xiaojiang");
pa.setMychild(ca);
String pid=pa.getId();

Session sess1=sessions.openSession();
tx=sess1.beginTransaction();
sess1.save(pa);
sess1.flush();
tx.commit();
sess1.close();

Session sess2=sessions.openSession();
tx=sess2.beginTransaction();
! here---> Parent pb=(Parent)sess2.load(com.dnt.test.Parent.class,pid);
if(pb==null){System.out.println("load return null");}
else{System.out.println("parent:"+pb.getName()
+"and his child:"+pb.getMychild().getName());
}
tx.commit();
sess2.close();

problem:

Hibernate: insert into CHILDS (NAME, id) values (?, ?)
Hibernate: insert into PARENTS (NAME, child_id, id) values (?, ?, ?)
Exception in thread "main" java.lang.NullPointerException: null is not a valid i
dentifier
at net.sf.hibernate.impl.SessionImpl.load(SessionImpl.java:1883)
at com.dnt.test.Test.main(Test.java:36)

anyone kown what is wrong with that?

At the time that this statement executes, pa is transient and has a null id.

so that means it's not usually that case that we load some persisitent entity by it's primary key ,cause primary key generated by the generator don't have real meaning ,instead most ofter find it not load it;
so load() method is not that usefull , is that right?????
in what situation the load() can be made grate use of ???

Execute the getId() after you have saved the object.