favorite java hibernate framework Job Interview Questions And Answers

Difference between get and load in Hibernate?

get vs load is one of the most frequently asked Hibernate Interview question, since correct understanding of both get() and load() is require to effectively using Hibernate. Main difference between get and load is that, get will hit the database if object is not found in the cache and returned completely initialized object, which may involve several database call while load() method can return proxy, if object is not found in cache and only hit database if any method other than getId() is called. This can save lot of performance in some cases. You can also see difference between get and load in Hibernate for more differences and detailed discussion on this question.

java hibernate framework   2013-08-14 14:45:26

Difference between save, persist and saveOrUpdate methods in Hibernate?

After get vs load, this is another Hibernate Interview question which appears quite often. All three methods i.e. save(), saveOrUpdate() and persist() is used to save objects into database, but has subtle differences e.g. save() can only INSERT records but saveOrUpdate() can either INSERT or UPDATE records. Also, return type of save() is a Serializable object, while return type of persist() method is void. You can also check save vs persist vs saveOrUpdate for complete differences between them in hibernate.

java hibernate framework   2013-08-14 14:45:57

What is named SQL query in Hibernate?

This Hibernate Interview question is related to query functionality provided by Hibernate. Named queries are SQL queries which are defined in mapping document using <sql-query> tag and called using Session.getNamedQuery() method. Named query allows you to refer a particular query by the name you provided, by the way you can define named query in hibernate either by using annotations or xml mapping file, as I said above. @NameQuery is used to define single named query and @NameQueries is used to define multiple named query in hibernate.

java hibernate framework   2013-08-14 14:46:18

What is SessionFactory in Hibernate? is SessionFactory thread-safe?

Another common Interview questions related to Hibernate framework. SessionFactory as name suggest is a factory to create hibernate Session objects. SessionFactory is often built during start-up and used by application code to get session object. It acts as single data store and its also thread-safe so that multiple thread can use same SessionFactory. Usually a Java JEE application has just one SessionFactory, and individual threads, which are servicing client’s request obtain hibernate Session instances from this factory, that’s why any implementation of SessionFactory interface must be thread-safe. Also internal state of SessionFactory, which contains all meta data about Object/Relational mapping is Immutable and can not be changed once created.

java hibernate framework   2013-08-14 14:46:50

What is Session in Hibernate? Can we share single Session among multiple threads in Hibernate?

This is usually asked as follow-up question of previous Hibernate Interview question. After SessionFactory its time for Session. Session represent a small unit of work in Hibernate, they maintain connection with database and they are not thread-safe, it means you can not share Hibernate Session between multiple threads. Though Session obtains database connection lazily it's good to close session as soon as you are done with it.

java hibernate framework   2013-08-14 14:47:21

What is difference between sorted and ordered collection in hibernate?

This is one of the easy Hibernate interview question you ever face. A sorted collection is sorted in memory by using Java Comparator, while a ordered collection uses database's order by clause for ordering. For large data set it's better to use ordered collection to avoid any OutOfMemoryError in Java, by trying to sort them in memory.

java hibernate framework   2013-08-14 14:48:10

What is Second level Cache in Hibernate?

java hibernate framework   2013-08-14 14:49:48

What is query cache in Hibernate ?

java hibernate framework   2013-08-14 14:50:30

Why it's important to provide no argument constructor in Hibernate Entities?

java hibernate framework   2013-08-14 14:50:56

What is difference between transient, persistent and detached object in Hibernate?

In Hibernate, Object can remain in three state transient, persistent or detached.  An object which is associated with Hibernate session is called persistent object. Any change in this object will reflect in database based upon your flush strategy i.e. automatic flush whenever any property of object change or explicit flushing by calling Session.flush() method. On the other hand if an object which is earlier associated with Session, but currently not associated with it are called detached object. You can reattach detached object to any other session by calling either update() or saveOrUpdate() method on that session. Transient objects are newly created instance of persistence class, which is never associated with any Hibernate Session. Similarly you can call persist() or save() methods to make transient object persistent. Just remember, here transient doesn’t represent transient keyword in Java, which is altogether different thing.

java hibernate framework   2013-08-14 14:48:42

What does Session lock() method do in Hibernate?

java hibernate framework   2013-08-14 14:49:12

Can we make an Hibernate Entity Class final?

java hibernate framework   2013-08-14 14:51:19