pc - a transient instance of a Class that implements PersistenceCapable
這是JDO-javadoc裏的對makePersistent的一段定義,PC,是一個瞬時化實例對象.
其實,一個Persistent new 實例也時可以makePersistent的,而一個Persistent Dirty實例則不行
測試代碼:
1.持久化Persistent new 對象
PersistenceManager pm = PersistenceManagerSource.distinctPM();
Transaction t = pm.currentTransaction();
t.begin();
userDAO.setPoClass(User.class);
try {
user = (User) userDAO.getObjectById(pm, id);//從DAO裏得到Persistent new User對象
pm.makePersistent(user);//持久化操作,本操作不出錯
pm.makeTransient(user);
} catch (DAOException e) {
if(t.isActive())
t.rollback();
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if(t.isActive())
t.commit();
if (pm != null)
pm.close();
}
return user;
2.持久化Persistent dirty對象
PersistenceManager pm = PersistenceManagerSource.distinctPM();
Transaction t = pm.currentTransaction();
t.begin();
userDAO.setPoClass(User.class);
try {
user = (User) userDAO.getObjectById(pm, id);//從DAO裏得到Persistent new User對象
user.setUserName(“JJYAO“);
pm.makePersistent(user);//持久化操作,本操作出錯
pm.makeTransient(user);
} catch (DAOException e) {
if(t.isActive())
t.rollback();
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if(t.isActive())
t.commit();
if (pm != null)
pm.close();
}
return user;