Hibernate Training Session1

What is Hibernate means?
Animals that sleep through the winter, like bears, squirrels, bat etc.
Hibernation is characterized by low body temperature, slow breathing and heart rate,
and low metabolic rate.

Can Human be Hibernate in
Future?
The extreme survival tricks of hibernating animals… and the occasional human…
could help us overcome life-threatening injuries, as Frank Swain discovers.

In Java world Hibernate is a well-
known ORM Framework
What is an ORM?
Object Relational Mapping (ORM) is a programming technique to access the data
from source which is incompatible with object orientated paradigm.
Why do we need ORM?
 Speeding development/Huge reduction in code.
 DBMS Compatibility
 Focus on Business more
 Make CRUD operation to behave OOP way
 Cache mechanism

Typical flow of an ORM
ORM act as a bridge b/w Object oriented application and relational database.

Other ORMs?
Is there any other ORMs?
 Eclipse Link
 Apache Cayenne
 Top Link
 Open JPA
Then Why Hibernate?
 Popularity
 Performance
 Vast support/Help
 Reliable
 JPA 2.1 compliant
 Cache support

Comparison with JDBC
Lets see their fight in eclipse IDE
HIBERNATE JDBC

Hibernate Core Classes Flow
Read
Configuration
and setup
hibernate
Manage Session
/Create Session
Make group of
dependent
instruction to
single
Execute single
instruction
Execute
HQL
Act as a
Where
clause

Closer look of Hibernate and JPA
Hibernate does more than JPA

What is JPA
History
 There were no standard for ORM until JPA introduced.
 JPA 1.0 was born in 2006 (Java EE 5)/ Influenced by Hibernate.
So What is it?
 JPA is a specification to standardize ORM-APIs or
specification for accessing, persisting and managing the data
between Java objects and the relational database.
 It means it went through the Java Community Process.
 Its specification # is JSR338
(https://jcp.org/en/jsr/detail?id=338)
 Following are implementation of JPA:
1)Eclipse Link 2) Hibernate 3)Open JPA
 These are interchangeable or no vendor locking.

Hibernate Setup
We will be using Hibernate version 4.3.7 in this training
and you can get from below link:
http://hibernate.org/orm/downloads
Hibernate JBOSS Tool for Eclipse:
http://download.jboss.org/jbosstools/updates/stable/lu
na/

Basic Setup for Hibernate
1. Create Java SE/EE Project.
2. Create Hibernate configuration file. Note: more
about this configuration file in next slide
3. Create Java Bean/ Class (Persistent Class).Note: more
about this class in next slide
4. Create Mapping File of that Class.
5. Map this class in Hibernate Configuration file.

Hibernate Configuration Properties
hibernate.use_sql_comments: true /false (true means show, false means don’t)
hibernate.format_sql: Pretty print the SQL in the log and console. e.g. true | false
hibernate.dialect: The classname of a Hibernate org.hibernate.dialect.Dialect
which allows Hibernate to generate SQL optimized for a particular relational
database.e.g. full.classname.of.Dialect
hibernate.show_sql: Write all SQL statements to console. This is an alternative to
setting the log category org.hibernate.SQL to debug.
e.g. true | false
hibernate.default_schema: Qualify unqualified table names with the given
schema/tablespace in generated SQL. e.g. SCHEMA_NAME
hibernate.hbm2ddl.auto: Automatically validates or exports schema DDL to the
database when the SessionFactory is created. With create-drop, the database
schema will be dropped when the SessionFactory is closed explicitly.
e.g. validate | update | create | create-drop

Following rules must be followed
when declaring Persistent Class
The four main rules of persistent classes :
 Implement a no-argument constructor
 Provide an identifier property (optional)
 Prefer non-final classes (optional)
 Declare accessors and mutators for persistent
fields (optional)
See the Employee class example in code.

Types of Generator in Hibernate
 Assigned: lets the application assign an identifier to the object before save() is
called. This is the default strategy if no <generator> element is specified.
 Identity: supports identity columns in DB2, MySQL, MS SQL Server, Sybase
and Hypersonic SQL. The returned identifier is of type long, short or int.
 Sequence: uses a sequence in DB2, PostgreSQL, Oracle, SAP DB, McKoi or a
generator in Interbase. The returned identifier is of type long, short or int.
 Uuid: uses a 128-bit UUID algorithm to generate identifiers of type string that
are unique within a network (the IP address is used). The UUID is encoded as a
string of 32 hexadecimal digits in length.
 Increment: generates identifiers of type long, short or int that are unique only
when no other process is inserting data into the same table.
There are many more classes for generator. Please visit the following site:
https://docs.jboss.org/hibernate/orm/3.3/reference/en/html/mapping.html

What is an Entity
 Entity : An entity is something that exists in itself,
actually or potentially, concretely or abstractly,
physically or not physically (conceptually).

Attribute
A property, or a conclusion of a characteristic of an entity
or substance or An attribute is a characteristic of
an entity.

Entity type or Value(Attribute) type
Any piece of data can be expressed as entity type or value
type:
 Entity Types:
Entities have a unique identity means exist independently and define
their own lifecycle., which stays the same despite of changes in the
properties of the object. For example Human, mobile, computer etc.

 Value Types
A value type do not define their own lifecycle. We say that they are
"owned" by something else (specifically an entity) which defines
their lifecycle. For Example: name, address, age of Employee, hand
of human, nip of a pen, wheel of a car, companies history of an
employee etc.
Value types are further classified into 3 sub-categories: basic types,
composite types and collection types.
• Basic Types: age, name, sex of an employee in single value.
• Composite types: aggregate values of basic types for i.e. address of
employee contain (country , state ,city and street).
• Collection types: collection of data for i.e. companies history of an
employee, daily activities of an employee.

Composite Value Type and its mapping with
an Entity
“Address” as a composite value type of an employee.
Lets see the example of mapping with an entity in code.
Collection Value Type and its mapping with
an Entity
In hibernate always declare a collection variable type by their
parent interface. For example Set, List, Map, Collection etc.
Because when we get back the collection object from
hibernate its type will be change by hibernate. It won’t be the
Java HashSet or ArrayList or HashMap, Its type will be in
specialized form.

Uni-directional and Bi-directional relationship
Uni-directional
Bi-directional
Recommended approach make relationship bidirectional in class.

Collection Value Type as HashSet Example
HashSet Properties:
 A Set represents a mathematical set.
 It is a Collection that, unlike List, does not allow
duplicates.
 There must not be two elements of a Set, say e1 and e2,
such that e1.equals(e2).
 The add method of Set returns false if you try to add a
duplicate element.
 HashSet allows at most one null element.
 HashSet is faster than other implementations of Set,
TreeSet and LinkedHashSet.
Lets see in action the “Employee Activities” as a collection
value type of an employee using HashSet in a program.

Collection Value Type as ArrayList Example
 An ArrayList is an ordered collection
 Permits null elements
 It is not synchronized
Lets see in action the “Past Companies” as a collection
value type of an employee using ArrayList in a program.

Collection Value Type as HashMap Example
 No guarantees as to the order of the map.
 Uniqueness guarantee.
 No guarantee that the order will remain constant.
 It is unsynchronized and permits nulls.
Lets see HashMap collection value type in an action
using “Employee Roles” in a program.

What's Next
Next we will do Entity relationship.
 One-to-one
 One-to-many
 Many-to-one

Hibernate Training Session1

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