What is saveOrUpdate in Hibernate?
hibernate. Session class methods, save & saveOrUpdate is, save generates a new identifier and results in an INSERT query, whereas saveOrUpdate does an INSERT or an UPDATE. Save method stores an object into the database. That means it insert an entry if the identifier doesn’t exist, else it will throw error.
What is the difference between session Save () and session saveOrUpdate () methods in Hibernate?
The main difference between save and saveOrUpdate method is that save() generates a new identifier and INSERT record into the database while saveOrUpdate can either INSERT or UPDATE based upon the existence of a record.
How do I use saveOrUpdate?
Using saveOrUpdate() The saveOrUpdate(), as the name implies, works as either save() or update() on the basis of the ID field present in the entity or not. In most cases, it is the preferred method to save(). If ID is not present then save() is called. If ID is present then update() is called.
What is difference between persist and merge?
Persist should be called only on new entities, while merge is meant to reattach detached entities. If you’re using the assigned generator, using merge instead of persist can cause a redundant SQL statement.
What is Session factory in hibernate?
The SessionFactory is a thread safe object and used by all the threads of an application. The SessionFactory is a heavyweight object; it is usually created during application start up and kept for later use. You would need one SessionFactory object per database using a separate configuration file.
What is difference between Merge and update in hibernate?
Hibernate handles persisting any changes to objects in the session when the session is flushed. update can fail if an instance of the object is already in the session. Merge should be used in that case. It merges the changes of the detached object with an object in the session, if it exists.
What is the difference between Session Save () and Session persist ()?
The persist() method will not execute an insert query if it is called outside of transaction boundaries. While, the save() method returns an identifier so that an insert query is executed immediately to get the identifier, no matter if it are inside or outside of a transaction.
What is Session flush in Hibernate?
Flushing the session forces Hibernate to synchronize the in-memory state of the Session with the database (i.e. to write changes to the database). By default, Hibernate will flush changes automatically for you: before some query executions. when a transaction is committed.
What is Session factory in Hibernate?
What is the difference between session Save () and session persist () method?
What is difference between save and Saveflush?
On saveAndFlush , changes will be flushed to DB immediately in this command. With save , this is not necessarily true, and might stay just in memory, until flush or commit commands are issued.
What is difference between session and session factory?
SessionFactory is a factory class for Session objects. It is available for the whole application while a Session is only available for particular transaction. Session is short-lived while SessionFactory objects are long-lived. SessionFactory provides a second level cache and Session provides a first level cache.
How many session factory are there in Hibernate?
You would need one SessionFactory object per database using a separate configuration file.
What is difference between getCurrentSession () and openSession () in hibernate?
openSession() always opens a new session that you have to close once you are done with the operations. SessionFactory. getCurrentSession() returns a session bound to a context – you don’t need to close this.
Is MERGE better than UPDATE?
Both the MERGE and UPDATE statements are designed to modify data in one table based on data from another, but MERGE can do much more. Whereas UPDATE can only modify column values you can use the MERGE statement to synchronize all data changes such as removal and addition of row.
What is lazy loading in hibernate?
Lazy setting decides whether to load child objects while loading the Parent Object. You need to do this setting respective hibernate mapping file of the parent class. Lazy = true (means not to load child)By default the lazy loading of the child objects is true.
What is difference between UPDATE and merge in hibernate?
What is difference between flush and commit in Hibernate?
Hibernate: Difference commit() vs flush(). flush(): Flushing is the process of synchronizing the underlying persistent store with persistable state held in memory.it will update or insert into your tables in the running transaction, but it may not commit those changes. Commit(): Commit will make the database commit.