Hibernate Interview Questins

8/8/2019 Hibernate Interview Questins

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1 Does Hibernate Session Object has any

cache associated with it by default ?

Yes, first-level caching is a mandatoryrequirement for Hibernate Session Object.

2 Is there any cache associated with

Hibernate SessionFactory Object?

Yes, there is an optional second-level cache

with Hibernate SessionFactory object.3 Can a single Hibernate Session object be

used across multiple threads running within a

process

No, Hibernate Session is basically single-

threaded and not to be used across multiplethreads.

4 Is this same for Hibernate SessionFactory

object as well?

No, Hibernate SessionFactory is basically

thread-safe, thus can be re-used acrossmultiple threads and multiple Transacions as

well.


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5 How can the second-level caching for

Hibernate SessionFactory object be disabled?

By setting appropriate hibernate.cacheconfiguration related properties, one can

enable/disable second-level caching for

Hibernate SessionFactory object

but only for once before SessionFactory is

created

6 Is it possible to use Hibernate Session

object with the scope and context defined by

JTA Transaction ?

Yes, starting with Hibernate 3.0.1 version,

Sessionfactory.getCurrentSession method has

the scope and context defined by the running

JTA Transaction scope and context. But as of

Hibernate 3.1 version, getCurrentSession

method of Hibernate

SessionFactory has the current Session Scope

and Context controlled by pluggable currentSession Context class, defined in

configuration parameter such as

hibernate.current_session_context_class.


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7 As of Hibernate 3.1 version can you be able

to explain how many ways scope and context

of Hibernate current contextual session be

handled?

As of Hibernate 3.1 version, Hibernate has

three ways to handle current contextual

session, such as

JTASessionContextThreadLocalSessionContext

ManagedSessionContext.

8 What is the difference between class tag

and component tag in Hibernate from the

persistence perspective?

class tag refers to an Entity that is persisted

with an identifier, while component tag means

the POJO associated with component tag is

persisted along with contained object as a

value type. So it doesn't require

an identifier, while the contained object has

an entity reference, not for the component

object.


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What is the difference between component

and dynamic component?

Component in Hibernate world, meanssomething that is embeded in

a contained object and there exist a

composition style of binding between

the contained object and the component

object. So component is declaredinside a class tag, just to say one type of use.

Dynamic-component has the same

characteristics as component but there exists

a difference in the way dynamic-component

can be used to map a bean's attribute, thiscan be of type java.util.Map with the key

defined in mapping file

and corresponding value from the table's

column.

So with dynamic-component, there can be

possibility of changing the attribute key/value

pair during deployment time, just by changing


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the name and column values in the mapping

configuration file.

9 Can a Hibernate Session, that isretrieved/created from a Hibernate

SessionFactory, be shared across multiple

concurrent Thread/Requests?

No, as Hibernate Session is not Thread-Safe,

so sharing it with multiple concurrent Thread

of execution or request will have concurrentcy

issues.

It is always better to use a single Hibernate

Session for a

single transaction, that means as long as the

transaction is running or not commited, a

single session can be used. As a Transaction

is running in isolation for each Thread or

request.

10 What is a good approach of handling

Hibernate Session, in case of any databaseexception or Hibernate Exception that is

occuring while a Hibernate Session is in use?


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As Hibernate Session caches Persistent

Object, in case of any Database exception or

Hibernate Exception occuring, then Session

cache might have some stale data or

Persistent Object not in sync with Database.

So it is always better to rollback Transaction,

close Session, in this circumtances.

11 How Hibernate manages Transaction

timeout in Managed and Non-managed

environments?

In Managed environment, that is JTA

transaction can handle timeout, so Hibernate

delegated Transaction timeout task to JTA

Transaction.

But in non-managed environment, Developer

has to explicitly specify Transaction timeout

parameter while using Transaction from

Hibernate Session by using setTimeOut(time

in seconds).But this feature cannot be fully compared

with JTA based Transaction timeout operation.


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Any one wants to comment on these

questions and answer, please do so.

12 What is the first level cache and thesecond level cache in Hibernate?

First level cache is associated with Hibernate

Session object, and is mandatory, while

second level cache is optionally associated

with Hibernate SessionFactory instance.

13 Which cache is cluster-level, first level or

second level?

Second level cache is optional, but can be

cluster-level.

How many different instance states exist foran instance of a persistent class while using

Hibernate?

There are three different instance states, such

as Transient, Persistent, and detached.

14 What are the instances having persistententity?

Persistent and detached instances are having

persistent entity. Can you please explain


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these three instance states with help of an

example?

Suppose in a web application, if a userinformation is passed from the registration

page shwon on browser for the first time, then

the UI helper class will be creating an instance

of the User class, and populate all the

relevant details onto the USER object. At this

level USER object has a Java identity but nopersistent identity. So this

USER object is transient instance state. Then

if this USER instance is sent to the business

level, and with help of DAO, is stored in

backend db, then this USER instance has gotboth Java and Persistent identities, so is

having Persistent instance state.

If this USER object is again sent to the UI level

for displaying an edit screen, then this USER

instance in UI tier is detached instance state,

as is having both Java and persistent identity.

But Hibernate cann't relate Java and

persistent identities for detached instance

states.


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Hibernate Interview Questins