Does JPA/Hibernate save even when not calling persist












8















em.getTransaction().begin();



StringData sd = em.find(StringData.class, key);

System.out.println("Old value: " + sd.getData());

sd.setData(newValue);

// em.persist(sd);



em.getTransaction().commit();


As you can see, I'm not calling persist, it's commented out, because I'm dry running this code first. However, as it turns out it's not so very dry. Upon inspecting the database, I see the data is changed (fortunately it's a test database).



Apparently my understanding of Hibernate/JPA is flawed. Isn't calling persist always required to change data? And if not, what are the rules on when something is saved?






java hibernate jpa







share|improve this question























  • but you are calling commit?

    – Sergey Benner
    Feb 8 '12 at 16:20
















8















em.getTransaction().begin();



StringData sd = em.find(StringData.class, key);

System.out.println("Old value: " + sd.getData());

sd.setData(newValue);

// em.persist(sd);



em.getTransaction().commit();


As you can see, I'm not calling persist, it's commented out, because I'm dry running this code first. However, as it turns out it's not so very dry. Upon inspecting the database, I see the data is changed (fortunately it's a test database).



Apparently my understanding of Hibernate/JPA is flawed. Isn't calling persist always required to change data? And if not, what are the rules on when something is saved?






java hibernate jpa







share|improve this question























  • but you are calling commit?

    – Sergey Benner
    Feb 8 '12 at 16:20














8












8








8








em.getTransaction().begin();



StringData sd = em.find(StringData.class, key);

System.out.println("Old value: " + sd.getData());

sd.setData(newValue);

// em.persist(sd);



em.getTransaction().commit();


As you can see, I'm not calling persist, it's commented out, because I'm dry running this code first. However, as it turns out it's not so very dry. Upon inspecting the database, I see the data is changed (fortunately it's a test database).



Apparently my understanding of Hibernate/JPA is flawed. Isn't calling persist always required to change data? And if not, what are the rules on when something is saved?






java hibernate jpa







share|improve this question














em.getTransaction().begin();



StringData sd = em.find(StringData.class, key);

System.out.println("Old value: " + sd.getData());

sd.setData(newValue);

// em.persist(sd);



em.getTransaction().commit();


As you can see, I'm not calling persist, it's commented out, because I'm dry running this code first. However, as it turns out it's not so very dry. Upon inspecting the database, I see the data is changed (fortunately it's a test database).



Apparently my understanding of Hibernate/JPA is flawed. Isn't calling persist always required to change data? And if not, what are the rules on when something is saved?






java hibernate jpa




java hibernate jpa






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Feb 8 '12 at 16:15









Bart van HeukelomBart van Heukelom

20.8k47154270




20.8k47154270













  • but you are calling commit?

    – Sergey Benner
    Feb 8 '12 at 16:20



















  • but you are calling commit?

    – Sergey Benner
    Feb 8 '12 at 16:20

















but you are calling commit?

– Sergey Benner
Feb 8 '12 at 16:20





but you are calling commit?

– Sergey Benner
Feb 8 '12 at 16:20












2 Answers
2






active

oldest

votes


















10














Yes, managed entities are saved when a flush (flush are also done with a commit) is done if any change is detected, it's called dirty checking.






share|improve this answer
























  • Good to know. Can that be relied upon, or is a persist call still wise?

    – Bart van Heukelom
    Feb 8 '12 at 16:25











  • @Bart Only managed entities are saved this way, managed means that the entity manager used to load those entities is not closed yet, so be careful. And persist works to create a new entity. If you use it in an already existing entity (like here) it will throw an exception. Take a look at the API: link

    – Pablo
    Feb 8 '12 at 16:32













  • But I use persist on loaded entities all the time, without exceptions.

    – Bart van Heukelom
    Feb 8 '12 at 16:43











  • @Bart Strange, in the API for persist: "EntityExistsException - if the entity already exists. (If the entity already exists, the EntityExistsException may be thrown when the persist operation is invoked, or the EntityExistsException or another PersistenceException may be thrown at flush or commit time.) "

    – Pablo
    Feb 8 '12 at 16:47








  • 1





    @Bart OK, it seems that the API is not very accurate, look at the accepted answer: link

    – Pablo
    Feb 8 '12 at 16:53





















3














StringData sd = em.find(StringData.class, key);


That line of code retrieves the StringData instance sd from the em session, any changes you make will be saved on flush (when transactions ends) because the object instance is associated with the em session (ie managed).



You could detach it, or return it from the method. Outside of the transaction it is not associated with em session and changes will not be persisted until it is re-attached via merge.






share|improve this answer
























  • The important part is not that the transaction is commited, the important part is that the entity manager is closed. If the transaction is commited but the entity manager is not closed, the entity is still associated with the entity manager.

    – Pablo
    Feb 8 '12 at 16:38











  • @Pablo So what happens if the entity is changed outside the transaction, but within the entity manager?

    – Bart van Heukelom
    Feb 8 '12 at 17:28











  • @Bart The entity manager will try to save it the next time that a flush() or commit() is called.

    – Pablo
    Feb 8 '12 at 17:50











Your Answer






StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f9197160%2fdoes-jpa-hibernate-save-even-when-not-calling-persist%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









10














Yes, managed entities are saved when a flush (flush are also done with a commit) is done if any change is detected, it's called dirty checking.






share|improve this answer
























  • Good to know. Can that be relied upon, or is a persist call still wise?

    – Bart van Heukelom
    Feb 8 '12 at 16:25











  • @Bart Only managed entities are saved this way, managed means that the entity manager used to load those entities is not closed yet, so be careful. And persist works to create a new entity. If you use it in an already existing entity (like here) it will throw an exception. Take a look at the API: link

    – Pablo
    Feb 8 '12 at 16:32













  • But I use persist on loaded entities all the time, without exceptions.

    – Bart van Heukelom
    Feb 8 '12 at 16:43











  • @Bart Strange, in the API for persist: "EntityExistsException - if the entity already exists. (If the entity already exists, the EntityExistsException may be thrown when the persist operation is invoked, or the EntityExistsException or another PersistenceException may be thrown at flush or commit time.) "

    – Pablo
    Feb 8 '12 at 16:47








  • 1





    @Bart OK, it seems that the API is not very accurate, look at the accepted answer: link

    – Pablo
    Feb 8 '12 at 16:53


















10














Yes, managed entities are saved when a flush (flush are also done with a commit) is done if any change is detected, it's called dirty checking.






share|improve this answer
























  • Good to know. Can that be relied upon, or is a persist call still wise?

    – Bart van Heukelom
    Feb 8 '12 at 16:25











  • @Bart Only managed entities are saved this way, managed means that the entity manager used to load those entities is not closed yet, so be careful. And persist works to create a new entity. If you use it in an already existing entity (like here) it will throw an exception. Take a look at the API: link

    – Pablo
    Feb 8 '12 at 16:32













  • But I use persist on loaded entities all the time, without exceptions.

    – Bart van Heukelom
    Feb 8 '12 at 16:43











  • @Bart Strange, in the API for persist: "EntityExistsException - if the entity already exists. (If the entity already exists, the EntityExistsException may be thrown when the persist operation is invoked, or the EntityExistsException or another PersistenceException may be thrown at flush or commit time.) "

    – Pablo
    Feb 8 '12 at 16:47








  • 1





    @Bart OK, it seems that the API is not very accurate, look at the accepted answer: link

    – Pablo
    Feb 8 '12 at 16:53
















10












10








10







Yes, managed entities are saved when a flush (flush are also done with a commit) is done if any change is detected, it's called dirty checking.






share|improve this answer













Yes, managed entities are saved when a flush (flush are also done with a commit) is done if any change is detected, it's called dirty checking.







share|improve this answer












share|improve this answer



share|improve this answer










answered Feb 8 '12 at 16:19









PabloPablo

3,39622443




3,39622443













  • Good to know. Can that be relied upon, or is a persist call still wise?

    – Bart van Heukelom
    Feb 8 '12 at 16:25











  • @Bart Only managed entities are saved this way, managed means that the entity manager used to load those entities is not closed yet, so be careful. And persist works to create a new entity. If you use it in an already existing entity (like here) it will throw an exception. Take a look at the API: link

    – Pablo
    Feb 8 '12 at 16:32













  • But I use persist on loaded entities all the time, without exceptions.

    – Bart van Heukelom
    Feb 8 '12 at 16:43











  • @Bart Strange, in the API for persist: "EntityExistsException - if the entity already exists. (If the entity already exists, the EntityExistsException may be thrown when the persist operation is invoked, or the EntityExistsException or another PersistenceException may be thrown at flush or commit time.) "

    – Pablo
    Feb 8 '12 at 16:47








  • 1





    @Bart OK, it seems that the API is not very accurate, look at the accepted answer: link

    – Pablo
    Feb 8 '12 at 16:53





















  • Good to know. Can that be relied upon, or is a persist call still wise?

    – Bart van Heukelom
    Feb 8 '12 at 16:25











  • @Bart Only managed entities are saved this way, managed means that the entity manager used to load those entities is not closed yet, so be careful. And persist works to create a new entity. If you use it in an already existing entity (like here) it will throw an exception. Take a look at the API: link

    – Pablo
    Feb 8 '12 at 16:32













  • But I use persist on loaded entities all the time, without exceptions.

    – Bart van Heukelom
    Feb 8 '12 at 16:43











  • @Bart Strange, in the API for persist: "EntityExistsException - if the entity already exists. (If the entity already exists, the EntityExistsException may be thrown when the persist operation is invoked, or the EntityExistsException or another PersistenceException may be thrown at flush or commit time.) "

    – Pablo
    Feb 8 '12 at 16:47








  • 1





    @Bart OK, it seems that the API is not very accurate, look at the accepted answer: link

    – Pablo
    Feb 8 '12 at 16:53



















Good to know. Can that be relied upon, or is a persist call still wise?

– Bart van Heukelom
Feb 8 '12 at 16:25





Good to know. Can that be relied upon, or is a persist call still wise?

– Bart van Heukelom
Feb 8 '12 at 16:25













@Bart Only managed entities are saved this way, managed means that the entity manager used to load those entities is not closed yet, so be careful. And persist works to create a new entity. If you use it in an already existing entity (like here) it will throw an exception. Take a look at the API: link

– Pablo
Feb 8 '12 at 16:32







@Bart Only managed entities are saved this way, managed means that the entity manager used to load those entities is not closed yet, so be careful. And persist works to create a new entity. If you use it in an already existing entity (like here) it will throw an exception. Take a look at the API: link

– Pablo
Feb 8 '12 at 16:32















But I use persist on loaded entities all the time, without exceptions.

– Bart van Heukelom
Feb 8 '12 at 16:43





But I use persist on loaded entities all the time, without exceptions.

– Bart van Heukelom
Feb 8 '12 at 16:43













@Bart Strange, in the API for persist: "EntityExistsException - if the entity already exists. (If the entity already exists, the EntityExistsException may be thrown when the persist operation is invoked, or the EntityExistsException or another PersistenceException may be thrown at flush or commit time.) "

– Pablo
Feb 8 '12 at 16:47







@Bart Strange, in the API for persist: "EntityExistsException - if the entity already exists. (If the entity already exists, the EntityExistsException may be thrown when the persist operation is invoked, or the EntityExistsException or another PersistenceException may be thrown at flush or commit time.) "

– Pablo
Feb 8 '12 at 16:47






1




1





@Bart OK, it seems that the API is not very accurate, look at the accepted answer: link

– Pablo
Feb 8 '12 at 16:53







@Bart OK, it seems that the API is not very accurate, look at the accepted answer: link

– Pablo
Feb 8 '12 at 16:53















3














StringData sd = em.find(StringData.class, key);


That line of code retrieves the StringData instance sd from the em session, any changes you make will be saved on flush (when transactions ends) because the object instance is associated with the em session (ie managed).



You could detach it, or return it from the method. Outside of the transaction it is not associated with em session and changes will not be persisted until it is re-attached via merge.






share|improve this answer
























  • The important part is not that the transaction is commited, the important part is that the entity manager is closed. If the transaction is commited but the entity manager is not closed, the entity is still associated with the entity manager.

    – Pablo
    Feb 8 '12 at 16:38











  • @Pablo So what happens if the entity is changed outside the transaction, but within the entity manager?

    – Bart van Heukelom
    Feb 8 '12 at 17:28











  • @Bart The entity manager will try to save it the next time that a flush() or commit() is called.

    – Pablo
    Feb 8 '12 at 17:50
















3














StringData sd = em.find(StringData.class, key);


That line of code retrieves the StringData instance sd from the em session, any changes you make will be saved on flush (when transactions ends) because the object instance is associated with the em session (ie managed).



You could detach it, or return it from the method. Outside of the transaction it is not associated with em session and changes will not be persisted until it is re-attached via merge.






share|improve this answer
























  • The important part is not that the transaction is commited, the important part is that the entity manager is closed. If the transaction is commited but the entity manager is not closed, the entity is still associated with the entity manager.

    – Pablo
    Feb 8 '12 at 16:38











  • @Pablo So what happens if the entity is changed outside the transaction, but within the entity manager?

    – Bart van Heukelom
    Feb 8 '12 at 17:28











  • @Bart The entity manager will try to save it the next time that a flush() or commit() is called.

    – Pablo
    Feb 8 '12 at 17:50














3












3








3







StringData sd = em.find(StringData.class, key);


That line of code retrieves the StringData instance sd from the em session, any changes you make will be saved on flush (when transactions ends) because the object instance is associated with the em session (ie managed).



You could detach it, or return it from the method. Outside of the transaction it is not associated with em session and changes will not be persisted until it is re-attached via merge.






share|improve this answer













StringData sd = em.find(StringData.class, key);


That line of code retrieves the StringData instance sd from the em session, any changes you make will be saved on flush (when transactions ends) because the object instance is associated with the em session (ie managed).



You could detach it, or return it from the method. Outside of the transaction it is not associated with em session and changes will not be persisted until it is re-attached via merge.







share|improve this answer












share|improve this answer



share|improve this answer










answered Feb 8 '12 at 16:26









NimChimpskyNimChimpsky

33.2k46168276




33.2k46168276













  • The important part is not that the transaction is commited, the important part is that the entity manager is closed. If the transaction is commited but the entity manager is not closed, the entity is still associated with the entity manager.

    – Pablo
    Feb 8 '12 at 16:38











  • @Pablo So what happens if the entity is changed outside the transaction, but within the entity manager?

    – Bart van Heukelom
    Feb 8 '12 at 17:28











  • @Bart The entity manager will try to save it the next time that a flush() or commit() is called.

    – Pablo
    Feb 8 '12 at 17:50



















  • The important part is not that the transaction is commited, the important part is that the entity manager is closed. If the transaction is commited but the entity manager is not closed, the entity is still associated with the entity manager.

    – Pablo
    Feb 8 '12 at 16:38











  • @Pablo So what happens if the entity is changed outside the transaction, but within the entity manager?

    – Bart van Heukelom
    Feb 8 '12 at 17:28











  • @Bart The entity manager will try to save it the next time that a flush() or commit() is called.

    – Pablo
    Feb 8 '12 at 17:50

















The important part is not that the transaction is commited, the important part is that the entity manager is closed. If the transaction is commited but the entity manager is not closed, the entity is still associated with the entity manager.

– Pablo
Feb 8 '12 at 16:38





The important part is not that the transaction is commited, the important part is that the entity manager is closed. If the transaction is commited but the entity manager is not closed, the entity is still associated with the entity manager.

– Pablo
Feb 8 '12 at 16:38













@Pablo So what happens if the entity is changed outside the transaction, but within the entity manager?

– Bart van Heukelom
Feb 8 '12 at 17:28





@Pablo So what happens if the entity is changed outside the transaction, but within the entity manager?

– Bart van Heukelom
Feb 8 '12 at 17:28













@Bart The entity manager will try to save it the next time that a flush() or commit() is called.

– Pablo
Feb 8 '12 at 17:50





@Bart The entity manager will try to save it the next time that a flush() or commit() is called.

– Pablo
Feb 8 '12 at 17:50


















draft saved

draft discarded




















































Thanks for contributing an answer to Stack Overflow!


  • Please be sure to answer the question. Provide details and share your research!

But avoid …



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f9197160%2fdoes-jpa-hibernate-save-even-when-not-calling-persist%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







-

Popular posts from this blog

Costa Masnaga

Image
.mw-parser-output .avviso .mbox-text-div>div,.mw-parser-output .avviso .mbox-text-full-div>div{font-size:90%}.mw-parser-output .avviso .mbox-image div{width:52px}.mw-parser-output .avviso .mbox-text-full-div .hide-when-compact{display:block} Questa voce o sezione sull'argomento Lombardia non cita le fonti necessarie o quelle presenti sono insufficienti . Puoi migliorare questa voce aggiungendo citazioni da fonti attendibili secondo le linee guida sull'uso delle fonti. Segui i suggerimenti del progetto di riferimento. Costa Masnaga comune Localizzazione Stato   Italia Regione Lombardia Provincia Lecco Amministrazione Sindaco Sabina Panzeri (Al centro il cittadino) dall'08/06/2009 Territorio Coordinate 45°46′N 9°17′E  /  45.766667°N 9.283333°E 45.766667; 9.283333  ( Costa Masnaga ) Coordinate: 45°46′N 9°17′E  /  45.766667°N 9.283333°E 45.766667; 9.283333  ( Costa Masnaga ) Altitudine 318 m s.l.m...
Read more

Fotorealismo

Image
Guerrino Boatto, Venice's St. Barnaba Church and canal Il fotorealismo è un genere di pittura basato sull'uso di una o più fotografie dalle quali l'artista prende le informazioni necessarie da utilizzare poi nel processo della creazione dell'opera, in genere ad olio o ad acrilico, al fine di avere un aspetto finale il più simile possibile alla fotografia. Indice 1 Storia 2 Lista dei fotorealisti 3 Note 4 Voci correlate 5 Altri progetti Storia | Il fotorealismo è un movimento che nasce negli Stati Uniti d'America alla fine degli anni sessanta [1] sulla scia della Pop Art [2] [3] [4] , e insieme condividono il carattere reazionario verso la travolgente ascesa dei media, che alla metà del ventesimo secolo si trasforma in un fenomeno di massa talmente imponente da minacciare il valore dell'immagine nell'arte. [5] [6] Ne consegue così che, colto il gesto d'inizio che fu della Pop Art, i fotorealisti aprono ad un ...
Read more

Sidney Franklin

Image
Questa voce sull'argomento registi statunitensi è solo un abbozzo . Contribuisci a migliorarla secondo le convenzioni di Wikipedia. Sidney Franklin, foto di Carl Van Vechten Oscar alla memoria Irving G. Thalberg 1943 Sidney Franklin , all'anagrafe Sidney Arnold Franklin , (San Francisco, 21 marzo 1893 – Santa Monica, 18 maggio 1972), è stato un regista, produttore cinematografico e attore statunitense. Il 20 giugno 1963, si sposò con l'attrice australiana Enid Bennett. Il matrimonio durò fino alla morte dell'attrice, il 14 maggio 1969 [1] Indice 1 Filmografia 1.1 Regista 1.2 Aiuto regia (parziale) 1.3 Produttore 1.4 Attore (parziale) 2 Note 3 Altri progetti 4 Collegamenti esterni Filmografia | Regista | The Baby , co-regia Chester M. Franklin (1915) The Rivals , co-regia Chester M. Franklin (1915) Little Dick's First Case , co-regia Chester M. Franklin (1915) Her Filmland Hero , co-...
Read more