String size = "L";
shirt.setSzeId(size);
int pid = (int) System.currentTimeMillis();
for (int i = 0; i < nPart; i++) {
Part part = new Part();
part.setPartName("Part");
part.getId().setPartNumber(pid++);
part.setShirt(shirt);
shirt.getParts().add(part);
}
em.persist(shirt);
tx.commit();
em.close();