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This article introduces the relevant knowledge of "how to understand the persistence of Hibernate objects". Many people will encounter this dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Hibernate object persistence class (persistent class) the newly instantiated object is Transient. We can make a Transient object Persistent by associating it with a session.

DomesticCat fritz = new DomesticCat (); fritz.setColor (Color.GINGER); fritz.setSex ('M'); fritz.setName ("Fritz"); Long generatedId = (Long) sess.save (fritz)

If the persistence identity (identifier) of the Cat is of type generated, the identifier is automatically generated and assigned to the cat when save () is called. If the persistence identity (identifier) of the Cat is of type assigned, or a compound primary key (composite key), then the identity (identifier) should be manually assigned to the cat before calling save (). You can also use persist () instead of save () according to the semantics defined in EJB3 early draft.

Additionally, you can use an overloaded version of the save () method.

DomesticCat Competition = new DomesticCat (); pk.setColor (Color.TABBY); pk.setSex ('F'); pk.setName ("Competition"); pk.setKittens (new HashSet ()); pk.addKitten (fritz); sess.save (Competition, new Long (1234))

If the objects you persist have associated objects (associated objects) (such as the kittens collection in the example above), then the order in which these objects (contention and kittens) are persisted is arbitrary (that is, you can persist kittens or contention first), unless you have NOT NULL constraints on the foreign key column. Hibernate does not violate foreign key constraints, but if you persist objects in the wrong order, you may violate NOT NULL constraints.

Usually you don't worry about these details, because you are likely to use the propagating Hibernate object persistence (transitive persistence) feature to automatically save those objects associated with them. In this way, there will be no violation of NOT NULL constraints-Hibernate will take care of everything.

That's all for "how to understand the persistence of Hibernate objects". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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