They are linked to a Session so Hibernate knows what has changed. No persistent representation in the database and no identifier value have been assigned to an object. Hibernate Query Language isa powerful query language its syntax is quite similar to database SQL language,compared with SQL, however, HQL is fully object-oriented and understands notions like inheritance, polymorphism and association. These are persistent and not connected to the Session object. Check the detailed post about Hibernate Second level Cache – Eh Cache.
Hence it’s common for applications to use the identifier as a convenient handle to a persistent object.In these cases you need to use merge for updates and persist for saviing. What are the Core interfaces of Hibernate framework? Session is a light weight and a non-thread safe and main function of the Session is to offer create, read and delete operations for instances of mapped entity classes. Decoupling the application code from the infrastructure frameworks is one of the many benefits of using POJOs. Version property is used in hibernate to know whether an object is in transient state or in detached state. Difference between the session.update() method and the session.lock() method? persist: As mentioned above, this is used on transient objects. The five core interfaces are used in just about every Hibernate application. Transient – Newly created object so not associated with any Session and database. Lazy-loading can help improve the performance significantly since often you won’t need the children and so they will not be loaded. You can use like this Session Factory session Factory = new Configuration ().configure ().build Session Factory (); Session session = session Session (); 10. Session Factory Interface is used to create session instances in hibernate. They also simplify development because rather than being forced to think about everything – business logic, persistence, transactions, etc. The session.lock() method simply reattaches the object to the session without checking or updating the database on the assumption that the database in sync with the detached object. Find the Hibernate Interview Questions and Answers which will be useful while attending the interview. Hibernate is a pure Java object-relational mapping (ORM) and persistence framework that allows you to map plain old Java objects to relational database tables using (XML) configuration files. save It will Persists an entity and will assign an identifier if one doesn’t exist. If no identifier exists, I believe an exception is thrown. If you are sure that the object exists then use load() else use get() methods.I didn’t cover all the concepts but i will cover rest of the concepts in part2 . Its purpose is to relieve the developer from a significant amount of relational data persistence-related programming tasks. Difference between different saving methods in Hibernate? merge Hibernate has following three Object states Transient, Detached and Persistant. load() method will throw an exception if the unique id is not found in the database but get() method will return null if the unique id is not found in the database. Difference between detached state and transient state Objects?The “Cascade” keyword is often appear on the collection mapping to manage the state of the collection automatically. Stock Daily Record sdr1 = (Stock Daily Record)session.get(Stock Daily Record.class, new Integer(56)); Stock Daily Record sdr2 = (Stock Daily Record)session.get(Stock Daily Record.class, new Integer(57)); session.delete(sdr1); session.delete(sdr2); The cascade=”delete-orphan” is declared in ‘stock Daily Records’ to enable the delete orphan cascade effect.In this tutorials, this one-to-many example will be used to demonstrate the cascade effect. When you save or update the Stock, it will remove those ‘stock Daily Records’ which already mark as removed.The given instance does not become associated with the session.This operation cascades to associated instances if the association is mapped with cascade=”merge”.In above example, ‘merged Persistent Emp Entity’ is new entity which is persistent.So if you want to any more change, then make in in ‘merged Persistent Emp Entity’ instance.