JDO - 在将模型对象传递给视图之前，我是否需要对其调用 DetachCopy？
我对分离复制的理解是，它会创建对象的副本，以便您可以在 PersistenceManager 不注意的情况下对其进行更改。
由于我在将模型对象传递到要使用的视图之前关闭了 PersistenceManager，因此在传递它之前我不必调用 detachCopy 或 makeTransient 之类的东西，不是吗？
我看过的例子确实称它为... 这是我从 http://code.google 查看的示例。 com/appengine/docs/java/datastore/creatinggettinganddeletingdata.html：
public Employee getEmployee(User user) {
PersistenceManager pm = PMF.get().getPersistenceManager();
Employee employee, detached = null;
try {
employee = pm.getObjectById(Employee.class,
"[email protected]");
// If you're using transactions, you can call
// pm.setDetachAllOnCommit(true) before committing to automatically
// detach all objects without calls to detachCopy or detachCopyAll.
detached = pm.detachCopy(employee);
} finally {
pm.close();
}
return detached;
}
My understanding of detach copy is that it makes a copy of your object so that you can make changes to it without the PersistenceManager noticing.
Since I close my PersistenceManager before passing the model object to the view to be used, I wouldn't have to call anything like detachCopy or makeTransient before passing it along would I?
The examples I looked at do call it though...
This is the example I looked at from http://code.google.com/appengine/docs/java/datastore/creatinggettinganddeletingdata.html:
public Employee getEmployee(User user) {
PersistenceManager pm = PMF.get().getPersistenceManager();
Employee employee, detached = null;
try {
employee = pm.getObjectById(Employee.class,
"[email protected]");
// If you're using transactions, you can call
// pm.setDetachAllOnCommit(true) before committing to automatically
// detach all objects without calls to detachCopy or detachCopyAll.
detached = pm.detachCopy(employee);
} finally {
pm.close();
}
return detached;
}
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您可以使用 PMF 属性自动分离对象，或者手动分离它们的副本，如示例所示。现在问题是什么？
You can have objects detached automatically using the PMF prop, or detach copies of them manually, as the example says. Now what was the question?
来自 http://db.apache.org/jdo/attach_detach.html
From http://db.apache.org/jdo/attach_detach.html