spring JPA 查询正常，但是em.persist(user)无效，但不报错?报错

RT

@Repository
public class LoginDaoImpl implements LoginDao{
@PersistenceContext
private EntityManager em;

@Override
public String login(User user){
String userCode = StringSimple.nullToEmpty(user.getUserCode());
String password = StringSimple.nullToEmpty(user.getPassword());
Query query = em.createNativeQuery("select * from T_user where userCode = '"+userCode+"'",User.class);
List result = query.getResultList();
if(result.size()!=1){
return "noneUser";//没有该用户  或  userCode重复
}else{
Iterator iterator = result.iterator();
User user_= (User)iterator.next();
String correctPassword = user_.getPassword();
if(StringSimple.equals(correctPassword,password)){
return "success";//密码正确登录成功
}else{
return "wrongPassword";//密码错误
}
}
}

@Override
public void add(User user){
em.persist(user);
}


}

但是调用add执行也不报错，但是数据就是不插入

求JPA达人！！！！！