8/6/2019 Introduction to Hibernate 2

1/26

Introduction to Hibernate2.0

8/6/2019 Introduction to Hibernate 2

2/26

Presentation Overview

Hibernate Overview

Architecture

Understanding Hibernate ORM Getting Started

Building an Application

Other useful stuffs

8/6/2019 Introduction to Hibernate 2

3/26

Hibernate Overview

HIBERNATE is an ORM ( Object-Relational-Mapping) technology.

It is an Open-Source and free technology ,developed in SourceForge.net.

Other ORM Tools:

TopLink is one such tool , subsequentlyadopted by Oracle and so proprietary.

Hibernate and OJB(Object-Relational-Bridge)from Apache are two well known ORM tools,open-source and free.

JDO, also falls within the same category.

8/6/2019 Introduction to Hibernate 2

4/26

Facts about Hibernate

Open Source Java Object-RelationalMapping Tool.

One step up from Direct JDBC access.

Generates SQL ,Relieves manual ResultSet handling and object conversion, and

Keeps application portable to all DB. Hibernate provides persistence as a

service, rather than as a framework .

8/6/2019 Introduction to Hibernate 2

5/26

Architecture

High level Design

8/6/2019 Introduction to Hibernate 2

6/26

Why ORM?

The main features include :

1. Less error-prone code2. Optimized performance all the time

3. Solves portability issues4. Reduce development time

The ultimate goal

Take advantage of those things that relational databases

do well , without leaving the Java language of objects /classes .I will say , the ultimate aim is - Do less work ,Happy DBA .

8/6/2019 Introduction to Hibernate 2

7/26

Getting Started With Hibernate

1. Download and Install Hibernate2. Hibernate is available for download at

http://www.hibernate.org/

3. Include the hibernate.jar file in the workingdirectory.

4. Place your JDBC driver jar file in the lib

directory.

5. Edit hibernate configuration files, specifying

values for your database (Hibernate will

create a schema automatically)

8/6/2019 Introduction to Hibernate 2

8/26

Rules for your class

Must have Bean-style getXXX() and setXXX()

Must have default constructor

Not final

Identifier recommended (not required) any primitive type

any primitive wrapper

String

Date user-defined class (good for existing tables with

composite keys)

8/6/2019 Introduction to Hibernate 2

9/26

Creating the mapping file

Defining a class

Defining relationships

8/6/2019 Introduction to Hibernate 2

10/26

class name=name.of.class

table=name_of_table

schema=database_schema

proxy=name.of.proxy.class

discrimator-value=val

mutable=true

polymorphism=implicit

dynamic-update=false

dynamic-insert=falsepersister=PersisterClass>

...

8/6/2019 Introduction to Hibernate 2

11/26

8/6/2019 Introduction to Hibernate 2

12/26

8/6/2019 Introduction to Hibernate 2

13/26

Simple Association (one-to-one)

One-to-one mapping

Java usage:

Bar myBar = Foo.getBar();

Mapping file:

...

Table Schema:

Foo Bar

id id

8/6/2019 Introduction to Hibernate 2

14/26

Simple Reference (many-to-one)

Java usage:

Set myBars = Foo.getBars();

Mapping file:

...

Table Schema:

Fooid bar_id

Bar

id

8/6/2019 Introduction to Hibernate 2

15/26

Basic Collection (one-to-many)

Java usage:

Set Foo.getBars()

Mapping file:

...

Table schema:

Fooid

Bar

id foo_id

8/6/2019 Introduction to Hibernate 2

16/26

Many-to-many mapping

Java usage:

Set myBars = Foo.getBars();

Mapping file:

...

Schema:

Foo

id

Bar

id

Foo_Bar

foo_id bar_id

8/6/2019 Introduction to Hibernate 2

17/26

Collection

Java usage:

Set myPeople = Foo.getPeople();

Mapping file:

...

Table Schema:

FooId

Person

foo_id name

8/6/2019 Introduction to Hibernate 2

18/26

Map

Java usage:

Map myAges = Foo.getAges();

Mapping file:

...

Table schema:Foo

id

Ages

Id name age

8/6/2019 Introduction to Hibernate 2

19/26

Hibernate.config.xml

com.mysql.jdbc.Driver

jdbc:mysql://localhost/hibernatetutorial

root

10

false

org.hibernate.dialect.MySQLDialect

update

8/6/2019 Introduction to Hibernate 2

20/26

Hibernate Query Language

Hibernate is equipped with an extremely

powerful query language that (quite

intentionally) looks very much like SQL.

But don't be fooled by the syntax; HQL is

fully object-oriented, understanding

notions like inheritence, polymorphism and

association.

8/6/2019 Introduction to Hibernate 2

21/26

Queries are case-insensitive, except for

names of Java classes and properties. So SeLeCT is the same as sELEct is the

same as SELECT but

org.hibernate.eg.FOO is not

org.hibernate.eg.Foo and foo.barSet is not

foo.BARSET.

8/6/2019 Introduction to Hibernate 2

22/26

Why to use HQL?

Full support for relational operations: HQL allows representingSQL queries in the form of objects. Hibernate Query Language usesClasses and properties instead of tables and columns.

Return result as Object: The HQL queries return the query

result(s) in the form of object(s), which is easy to use. Thiselemenates the need of creating the object and populate the datafrom result set.

Polymorphic Queries: HQL fully supports polymorphic queries.Polymorphic queries results the query results along with all the childobjects if any.

Easy to Learn: Hibernate Queries are easy to learn and it can beeasily implemented in the applications.

8/6/2019 Introduction to Hibernate 2

23/26

Understanding HQL Syntax

Any Hibernate Query Language may consist

of following elements:

Clauses Aggregate functions

Subqueries

8/6/2019 Introduction to Hibernate 2

24/26

Clauses in the HQL are:

from

select

where order by

group by

8/6/2019 Introduction to Hibernate 2

25/26

8/6/2019 Introduction to Hibernate 2

26/26

Thank You