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PO
 

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    <p>Here's my understanding of the methods. Mainly these are based on the <a href="http://www.hibernate.org/hib_docs/v3/api/org/hibernate/Session.html" rel="noreferrer">API</a> though as I don't use all of these in practice.</p> <p><strong>saveOrUpdate</strong> Calls either save or update depending on some checks. E.g. if no identifier exists, save is called. Otherwise update is called.</p> <p><strong>save</strong> Persists an entity. Will assign an identifier if one doesn't exist. If one does, it's essentially doing an update. Returns the generated ID of the entity.</p> <p><strong>update</strong> Attempts to persist the entity using an existing identifier. If no identifier exists, I believe an exception is thrown.</p> <p><strong>saveOrUpdateCopy</strong> This is deprecated and should no longer be used. Instead there is...</p> <p><strong>merge</strong> Now this is where my knowledge starts to falter. The important thing here is the difference between transient, detached and persistent entities. For more info on the object states, <a href="http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/objectstate.html" rel="noreferrer">take a look here</a>. With save &amp; update, you are dealing with persistent objects. They are linked to a Session so Hibernate knows what has changed. But when you have a transient object, there is no session involved. In these cases you need to use merge for updates and persist for saving.</p> <p><strong>persist</strong> As mentioned above, this is used on transient objects. It does not return the generated ID.</p>
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    1. POWhat are the differences between the different saving methods in Hibernate?
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    1. USLee Theobald
    1. USLee Theobald
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    1. POWhat are the differences between the different saving methods in Hibernate?
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    1. COI'd like to accept this as the answer, but one thing is still unclear: since save() falls back on update(), if such item exists, how does it differ from saveOrUpdate() in practice?
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      1. USHenrik Paul
    2. COWhere is it specified, that save would work on detached instances?
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      1. USjrudolph
    3. COIf your description of merge/persist only being important on transient objects then this makes a ton of sense and fits with how we use hibernate. Also note a merge often has performance limitations compared to an update as it seems to do extra fetching for integrity checks of some sort.
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      1. USMartin Dale Lyness
 

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