Hibernate Interview Questions

What are the benefits of ORM and Hibernate?

There are many benefits from these. Out of which the following are the most important one.
i.    Productivity - Hibernate reduces the burden of developer by providing much of the functionality and let the developer to concentrate on business logic.
ii.    Maintainability - As hibernate provides most of the functionality, the LOC for the application will be reduced and it is easy to maintain. By automated object/relational persistence it even reduces the LOC.
iii.    Performance - Hand-coded persistence provided greater performance than automated one. But this is not true all the times. But in hibernate, it provides more optimization that works all the time there by increasing the performance. If it is automated persistence then it still increases the performance.
iv.    Vendor independence - Irrespective of the different types of databases that are there, hibernate provides a much easier way to develop a cross platform application.

How does hibernate code looks like?

Sessionsession= getSessionFactory().openSession();

Transaction tx = session.beginTransaction();
MyPersistanceClass mpc = new MyPersistanceClass ("Sample App");
session.save(mpc);
tx.commit();
session.close();
The Session and Transaction are the interfaces provided by hibernate. There are many other interfaces besides this.

What is a hibernate xml mapping document and how does it look like?

In order to make most of the things work in hibernate, usually the information is provided in an xml document. This document is called as xml mapping document. The document defines, among other things, how properties of the user defined persistence classes' map to the columns of the relative tables in database.
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>
  <classname="sample.MyPersistanceClass"table="MyPersitaceTable">
     <idname="id"column="MyPerId">
        <generatorclass="increment"/>
     </id>
     <propertyname="text"column="Persistance_message"/>
     <many-to-onename="nxtPer"cascade="all"column="NxtPerId"/>
  </class>
</hibernate-mapping>
Everything should be included under <hibernate-mapping> tag. This is the main tag for an xml mapping document.

1

2

3

4