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總結什麼我迄今發現通過不同的計算器帖子：休眠節省VS saveOrUpdate VS更新VS堅持
Persist
New
a) out of transaction: allowed. persist accomplished the task of saving both Parent and Child in one call.
b) in of transaction: allowed.
detached
a) out of transaction: allowed. will throw exception when trying to flush.
b) in of transaction: not allowed. will throw exception when trying to flush.
existing
a) out of transaction: allowed. will throw exception when trying to flush.
b) in of transaction: not allowed. will throw exception when trying to flush.
saveOrUpdate
new
a) out of transaction: allowed. will save.
b) in or transaction: allowed. will save.
detached
a) out of transaction: allowed. will update.
b) in of transaction: allowed. will update.
existing
a) out of transaction: allowed. will update.
b) in of transaction: allowed. will update.
save
new
a) out of transaction: allowed. will save. Not sure how can it be saved right away without transaction. save does not cascade to the child, i.e., only Parent is saved/inserted in the table.
b) in or transaction: allowed. will save.
detached
a) out of transaction: save() for a detached object will create a new row in the table.
b) in or transaction: not allowed. will throw exception.
existing
a) out of transaction: not sure what will happen.
b) in or transaction: not allowed. will throw exception.
update
new
a) out of transaction: not sure what will happen. should throw exception.
b) in or transaction: not sure what will happen. should throw exception.
detached
a) out of transaction: allowed. will update later during flush.
b) in or transaction: allowed. will update later during flush.
existing
a) out of transaction: allowed. will update later during flush.
b) in or transaction: allowed. will update later during flush.
merge
new
a) out of transaction: not sure what will happen.
b) in or transaction: if there is no persistent instance currently associated with the session, try to load it from the database, or create a new persistent instance.
detached
a) out of transaction: allowed. will update later during flush. return a copy.
b) in or transaction: allowed. will update later during flush. return a copy.
existing
a) out of transaction: allowed. will update later during flush. return a copy.
b) in or transaction: allowed. will update later during flush. return a copy.
對於指定的標識符的實體：
保存（）：它會立即返回一個實體的標識符。由於標識符在調用保存之前已被分配給實體，所以插入不會立即觸發。它在會話刷新時被觸發。
persist（）：與保存相同。它也在沖洗時發射插入。
請確認理解是否正確。
Hibernate persist() vs save() method Hibernate saveOrUpdate vs update vs save/persist Hibernate persist vs save What's the advantage of persist() vs save() in Hibernate? http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/objectstate.html