以下答案没有一个是正确的。 所有这些方法看似相似，但实际上做的事情完全不同。 很难给出简短的评论。最好提供关于这些方法的完整文档链接: http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/objectstate.html

实际上，hibernate save()和persist()方法之间的区别取决于我们使用的生成器类。

If our generator class is assigned, then there is no difference between save() and persist() methods. Because generator ‘assigned’ means, as a programmer we need to give the primary key value to save in the database right [ Hope you know this generators concept ] In case of other than assigned generator class, suppose if our generator class name is Increment means hibernate it self will assign the primary key id value into the database right [ other than assigned generator, hibernate only used to take care the primary key id value remember ], so in this case if we call save() or persist() method then it will insert the record into the database normally But hear thing is, save() method can return that primary key id value which is generated by hibernate and we can see it by

long s = session.save(k);

在同样的情况下，persist()将永远不会向客户端返回任何值。

╔══════════════╦═══════════════════════════════╦════════════════════════════════╗
║    METHOD    ║            TRANSIENT          ║            DETACHED            ║
╠══════════════╬═══════════════════════════════╬════════════════════════════════╣
║              ║       sets id if doesn't      ║   sets new id even if object   ║
║    save()    ║     exist, persists to db,    ║    already has it, persists    ║
║              ║    returns attached object    ║ to DB, returns attached object ║
╠══════════════╬═══════════════════════════════╬════════════════════════════════╣
║              ║       sets id on object       ║             throws             ║
║   persist()  ║     persists object to DB     ║       PersistenceException     ║
║              ║                               ║                                ║
╠══════════════╬═══════════════════════════════╬════════════════════════════════╣
║              ║                               ║                                ║
║   update()   ║           Exception           ║     persists and reattaches    ║
║              ║                               ║                                ║
╠══════════════╬═══════════════════════════════╬════════════════════════════════╣
║              ║  copy the state of object in  ║    copy the state of obj in    ║
║    merge()   ║     DB, doesn't attach it,    ║      DB, doesn't attach it,    ║
║              ║    returns attached object    ║     returns attached object    ║
╠══════════════╬═══════════════════════════════╬════════════════════════════════╣
║              ║                               ║                                ║
║saveOrUpdate()║           as save()           ║            as update()         ║
║              ║                               ║                                ║
╚══════════════╩═══════════════════════════════╩════════════════════════════════╝

See the Hibernate Forum for a explanation of the subtle differences between persist and save. It looks like the difference is the time the INSERT statement is ultimately executed. Since save does return the identifier, the INSERT statement has to be executed instantly regardless of the state of the transaction (which generally is a bad thing). Persist won't execute any statements outside of the currently running transaction just to assign the identifier. Save/Persist both work on transient instances, ie instances which have no identifier assigned yet and as such are not saved in the DB. Update and Merge both work on detached instances, ie instances which have a corresponding entry in the DB but which are currently not attached to (or managed by) a Session. The difference between them are what happens to the instance which is passed to the function. update tries to reattach the instance, that means that there must be no other instance of the persistent entity attached to the Session right now, otherwise an exception is thrown. merge, however, just copies all values to a persistent instance in the Session (which will be loaded if it is not currently loaded). The input object is not changed. So merge is more general than update, but may use more resources.

以下答案没有一个是正确的。 所有这些方法看似相似，但实际上做的事情完全不同。 很难给出简短的评论。最好提供关于这些方法的完整文档链接: http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/objectstate.html

以下是我对这些方法的理解。这些主要是基于API的，尽管我在实践中没有使用所有这些。

saveOrUpdate 根据某些检查调用save或update。例如，如果不存在标识符，则调用save。否则调用update。

保存 持久化一个实体。如果标识符不存在，将分配标识符。如果有，它本质上是在进行更新。返回生成的实体ID。

更新 尝试使用现有标识符持久化实体。如果不存在标识符，则抛出异常。

saveOrUpdateCopy 这已弃用，不应再使用。取而代之的是……

合并 现在我的知识开始动摇了。这里重要的是瞬态实体、分离实体和持久实体之间的区别。有关对象状态的更多信息，请查看这里。使用save & update，你处理的是持久对象。它们被链接到一个会话，因此Hibernate知道发生了什么变化。但是当你有一个瞬态对象时，就不涉及会话了。在这些情况下，您需要使用合并进行更新，使用持久化进行保存。

坚持 如上所述，这用于瞬态对象。它不返回生成的ID。