KEMBAR78
Hibernate for Beginners | PPT
Hibernate Kick off
1.
2.
3.
4.
5.
6.
7.

Hibernate Introduction
Why to use Hibernate
Steps to use/configure hibernate in an application
simple case study
Transaction in Hibernate
Using Criteria in Hibernate
Caching in Hibernate
Hibernate Introduction:
Hibernate is a powerful, high performance object/relational persistence and
query service. Hibernate lets you develop persistent classes following objectoriented idiom - including association, inheritance, polymorphism, composition,
and collections. Hibernate allows you to express queries in its own portable
SQL extension (HQL), as well as in native SQL, or with an object-oriented
Criteria and Example API.
 
 Object/Relational Mapping Hibernate Dual-Layer Cache Architecture
 Highly scalable architecture
 J2EE integration
 Object Relational tool ( JDO, Hibernate, and iBatis SQL Maps, TopLink)
 
Hibernate supports these following databases:
Why to use Hibernate
In traditional approach:
o Too many SQL statements
o Manually handled associations
o Database dependent
Hibernate architecture
Steps to use/configure hibernate in an application:

A. Installing the Hibernate core and support JAR libraries into your project
B.

Creating a Hibernate.cfg.xml file to describe how to access your database

C.

Selecting appropriate SQL Dialect for the database.

D.

Creating individual mapping descriptor files for each persistable Java
classes
Steps to use Hibernate

A. Install the Hibernate core and JAR libraries
Steps to use Hibernate

B. Creating a Hibernate.cfg.xml :
Before Hibernate can retrieve and persist objects for us, we need to tell it the
settings about our application. For example,





which kind of objects are persistent objects?
Which kind of database are we using?
How to connect to the database?
What is the size of Connection pool?

There are three ways to configure Hibernate in total:
1.      XML configuration
2.       programmatic configuration
3.       properties file configuration.
9. Steps to use Hibernate

XML Configuration
Steps to use Hibernate

C.
Selecting appropriate SQL Dialect for the
database.
The dialect property determines the dialect to be used when generating
queries. Hibernate supports dialects for all popular Relational Database
Management Systems (RDBMS), such as DB2 or Oracle™. Therefore, for
example, if you use Oracle during development and want to move to DB2 in
production, changes will only be required in the hibernate.cfg.xml file.
Steps to use Hibernate

A.    Creating individual mapping/descriptor files for
each persistable Java classes/Table in DB

Table

JAVA
POJO Class

XML

HBM File

RDBMS

A
12. Steps to use Hibernate

A Table in Database

 
 
 

CREATE TABLE BOOK (
 
 ISBN   VARCHAR(50) NOT NULL,
 
 NAME VARCHAR(100) NOT NULL,
 
 PRICE INT  NOT NULL,
 
PRIMARY KEY (ISBN)
 
);
Steps to use Hibernate

Java (POJO):
Steps to use Hibernate

Hibernate-mapping: (*.hbm.xml)

0
4

simple case study
simple case study
Creating global session factory:
For an application using Hibernate as O/R mapping framework, a global
session factory should be created and accessed through a particular interface.
Here we use a static variable for storing the session factory. It is initialized in a
static block when this class is loaded for the first time.
Simple Case Study

Using the SessionFactory in Application:
 
SessionFactory factory = HibernateUtil.getSessionFactory();
 
Session session = factory.openSession();  
try {

} finally {

//…………………..
// Using the session to retrieve objects
//……………………………….
session.close();

}
SessionFactorys are immutable. The behaviour of a SessionFactory is
controlled by properties supplied at configuration time.
Simple Case Study

Retrieving objects
 

Book book = (Book)
session.load(Book.class, isbn);
or
Book book = (Book) session.get(Book.class,
isbn);
 

What’s the difference between load() and get() ?
The first difference is that when the given ID could not be found, load() will
throw an exception “org.hibernate.ObjectNotFoundException”, while get() will
return a null object.
The second difference is that load() just returns a proxy by default and
database won’t be hit until the proxy is first invoked. The get() will hit the
database immediately.
19. Simple Case Study

Using HQL (Hibernate Query Language):

If you are sure that there will be only one object matching, you can use the
uniqueResult() method to retrieve the unique result object.

So, the code would appear as:
20. Simple Case Study

persisting Objects:
 
For saving a newly created object, we can use the save() method. Hibernate
will issue an INSERT statement.
 
session.save(book);
 
For updating an existing object, we can use the update() method. Hibernate will
issue an UPDATE statement.
 
session.update(book);
 
For deleting an existing object, we can use the delete() method. Hibernate will
issue a DELETE statement.
 
session.delete(book);
Id Generation in Hibernate
Simple Case Study

ID generation in Hibernate

 
There are three approaches to set ID:

 

a. Sequence
b. Identity
c.

Native
23. Simple Case Study

ID generation in Hibernate

 
There are three approaches to set ID:

 
a.Sequence

To generate an ID is to use an auto-incremented sequence number. For some
kinds of databases (including HSQLDB), we can use a sequence/generator to
generate this sequence number:
Simple Case Study

b. Identity:
To generate an auto-incremented sequence
number is to use an identity column of a table.
25. Simple Case Study

c. Native:
most suitable strategy to use for your database
26. Simple Case Study

primary key generation using multiple columns:
Table:
27. Simple Case Study

Java (POJO Class)
28. Simple Case Study

Mapping (an HBM file)
5. Transaction in Hibernate:
Transaction in Hibernate:
31. Transaction in Hibernate

Example : select
32. Transaction in Hibernate

Example : update
Transaction in Hibernate

Example : delete
6 Using Criteria in Hibernate
35. Transaction in Hibernate

Sometimes we need to build up a query dynamically in our application,
e.g. for an advanced search function.“Criteria Queries” is an alternative
way of HQL query.The traditional method of doing this is to generate a HQL
statement, or SQL statement if not using Hibernate, by string
concatenation. The problem for this method is making your code hard to
maintain because of the hard reading statement fragments.

Traditinal approach:
if (startDate != null) {
if (firstClause) {
query = query + " where ";
} else {
query = query + " and ";
query += " s.date >= '" + startDate + "'";
}
// And so on...
Transaction in Hibernate

Hibernate Criteria:
Criteria criteria = session.createCriteria(Book.class);
if (startDate != null) {
criteria.add(Expression.ge("date",startDate);
}
if (endDate != null) {
criteria.add(Expression.le("date",endDate);
}
List results = criteria.list();
37. Transaction in Hibernate

SELECT * FROM ORDERS WHERE ORDER_ID=’1092’;
In Cretira it would become:
List orders= session.createCriteria(Order.class)
.add(Restrictions.eq(“orderId”,”1092”))
.list();
SELECT O.*, P.* FROM ORDERS O, PRODUCT P WHERE
O.ORDER_ID=P.ORDER_ID AND P.ID=’1111’;
Would become
List orders = session.createCriteria(Order.class)
.setFetchMode(“products”,FetchMode.JOIN)
.add(Restrictions.eq(“id”,”1111”))
.list();
38. Transaction in Hibernate

This criteria query corresponds to the following HQL query:

from Book book
where book.name = 'Hibernate for Beginners'
39. Transaction in Hibernate

•Restriction.between is used to apply a "between" constraint to the field.
•Restriction.eq is used to apply an "equal" constraint to the field.
•Restriction.ge is used to apply a "greater than or equal" constraint to the field.
•Restriction.gt is used to apply a "greater than" constraint to the field.
•Restriction.idEq is used to apply an "equal" constraint to the identifier
property.
•Restriction.in is used to apply an "in" constraint to the field.
•Restriction.isNotNull is used to apply an "is not null" constraint to the field.
•Restriction.isNull is used to apply an "is null" constraint to the field.
•Restriction.ne is used to apply a "not equal" constraint to the field.
IN:
criteria.add(Restrictions.in("newCourseID", courseIDs));
 

7. Caching in Hibernate:
41. Caching in Hibernate

Hibernate supports the caching of persistent
objects at different levels:
1 st level of caching
2 nd Level of caching
42. Caching in Hibernate

1. 1st level of caching:
 
Suppose we get an object with same identifier
for two times within a session, will Hibernate
query the database for two times? 
43. Caching in Hibernate

If we inspect the SQL statements executed by
Hibernate, we will find that only one database
query is made. That means Hibernate is caching
our objects in the same session. This kind of
caching is called “first level caching”, whose
caching scope is a session.
 
But how about getting an object with same
identifier for two times in two different sessions?
44. Caching in Hibernate

2 nd Level of caching:
45. Caching in Hibernate

 We will find that two database queries are made.
That means Hibernate is not caching the
persistent objects across different sessions by
default.
We need to turn on this “second level caching”
whose caching scope is a session factory.
46 Caching in Hibernate

To enable 2nd level of caching, update the ‘hibernate.cfg.xml’

To monitor the caching activities of Hibernate at runtime, we can add the
following line to the log4j configuration file “log4j.properties”.
log4j.logger.org.hibernate.cache=debug
Thank you.

Hibernate for Beginners

  • 1.
  • 2.
    1. 2. 3. 4. 5. 6. 7. Hibernate Introduction Why touse Hibernate Steps to use/configure hibernate in an application simple case study Transaction in Hibernate Using Criteria in Hibernate Caching in Hibernate
  • 3.
    Hibernate Introduction: Hibernate isa powerful, high performance object/relational persistence and query service. Hibernate lets you develop persistent classes following objectoriented idiom - including association, inheritance, polymorphism, composition, and collections. Hibernate allows you to express queries in its own portable SQL extension (HQL), as well as in native SQL, or with an object-oriented Criteria and Example API.    Object/Relational Mapping Hibernate Dual-Layer Cache Architecture  Highly scalable architecture  J2EE integration  Object Relational tool ( JDO, Hibernate, and iBatis SQL Maps, TopLink)   Hibernate supports these following databases:
  • 4.
    Why to useHibernate In traditional approach: o Too many SQL statements o Manually handled associations o Database dependent
  • 5.
  • 6.
    Steps to use/configurehibernate in an application: A. Installing the Hibernate core and support JAR libraries into your project B. Creating a Hibernate.cfg.xml file to describe how to access your database C. Selecting appropriate SQL Dialect for the database. D. Creating individual mapping descriptor files for each persistable Java classes
  • 7.
    Steps to useHibernate A. Install the Hibernate core and JAR libraries
  • 8.
    Steps to useHibernate B. Creating a Hibernate.cfg.xml : Before Hibernate can retrieve and persist objects for us, we need to tell it the settings about our application. For example,     which kind of objects are persistent objects? Which kind of database are we using? How to connect to the database? What is the size of Connection pool? There are three ways to configure Hibernate in total: 1.      XML configuration 2.       programmatic configuration 3.       properties file configuration.
  • 9.
    9. Steps touse Hibernate XML Configuration
  • 10.
    Steps to useHibernate C. Selecting appropriate SQL Dialect for the database. The dialect property determines the dialect to be used when generating queries. Hibernate supports dialects for all popular Relational Database Management Systems (RDBMS), such as DB2 or Oracle™. Therefore, for example, if you use Oracle during development and want to move to DB2 in production, changes will only be required in the hibernate.cfg.xml file.
  • 11.
    Steps to useHibernate A.    Creating individual mapping/descriptor files for each persistable Java classes/Table in DB Table JAVA POJO Class XML HBM File RDBMS A
  • 12.
    12. Steps touse Hibernate A Table in Database       CREATE TABLE BOOK (    ISBN   VARCHAR(50) NOT NULL,    NAME VARCHAR(100) NOT NULL,    PRICE INT  NOT NULL,   PRIMARY KEY (ISBN)   );
  • 13.
    Steps to useHibernate Java (POJO):
  • 14.
    Steps to useHibernate Hibernate-mapping: (*.hbm.xml) 0
  • 15.
  • 16.
    simple case study Creatingglobal session factory: For an application using Hibernate as O/R mapping framework, a global session factory should be created and accessed through a particular interface. Here we use a static variable for storing the session factory. It is initialized in a static block when this class is loaded for the first time.
  • 17.
    Simple Case Study Usingthe SessionFactory in Application:   SessionFactory factory = HibernateUtil.getSessionFactory();   Session session = factory.openSession();   try { } finally { //………………….. // Using the session to retrieve objects //………………………………. session.close(); } SessionFactorys are immutable. The behaviour of a SessionFactory is controlled by properties supplied at configuration time.
  • 18.
    Simple Case Study Retrievingobjects   Book book = (Book) session.load(Book.class, isbn); or Book book = (Book) session.get(Book.class, isbn);   What’s the difference between load() and get() ? The first difference is that when the given ID could not be found, load() will throw an exception “org.hibernate.ObjectNotFoundException”, while get() will return a null object. The second difference is that load() just returns a proxy by default and database won’t be hit until the proxy is first invoked. The get() will hit the database immediately.
  • 19.
    19. Simple CaseStudy Using HQL (Hibernate Query Language): If you are sure that there will be only one object matching, you can use the uniqueResult() method to retrieve the unique result object. So, the code would appear as:
  • 20.
    20. Simple CaseStudy persisting Objects:   For saving a newly created object, we can use the save() method. Hibernate will issue an INSERT statement.   session.save(book);   For updating an existing object, we can use the update() method. Hibernate will issue an UPDATE statement.   session.update(book);   For deleting an existing object, we can use the delete() method. Hibernate will issue a DELETE statement.   session.delete(book);
  • 21.
  • 22.
    Simple Case Study IDgeneration in Hibernate   There are three approaches to set ID:   a. Sequence b. Identity c. Native
  • 23.
    23. Simple CaseStudy ID generation in Hibernate   There are three approaches to set ID:   a.Sequence To generate an ID is to use an auto-incremented sequence number. For some kinds of databases (including HSQLDB), we can use a sequence/generator to generate this sequence number:
  • 24.
    Simple Case Study b.Identity: To generate an auto-incremented sequence number is to use an identity column of a table.
  • 25.
    25. Simple CaseStudy c. Native: most suitable strategy to use for your database
  • 26.
    26. Simple CaseStudy primary key generation using multiple columns: Table:
  • 27.
    27. Simple CaseStudy Java (POJO Class)
  • 28.
    28. Simple CaseStudy Mapping (an HBM file)
  • 29.
  • 30.
  • 31.
    31. Transaction inHibernate Example : select
  • 32.
    32. Transaction inHibernate Example : update
  • 33.
  • 34.
    6 Using Criteriain Hibernate
  • 35.
    35. Transaction inHibernate Sometimes we need to build up a query dynamically in our application, e.g. for an advanced search function.“Criteria Queries” is an alternative way of HQL query.The traditional method of doing this is to generate a HQL statement, or SQL statement if not using Hibernate, by string concatenation. The problem for this method is making your code hard to maintain because of the hard reading statement fragments. Traditinal approach: if (startDate != null) { if (firstClause) { query = query + " where "; } else { query = query + " and "; query += " s.date >= '" + startDate + "'"; } // And so on...
  • 36.
    Transaction in Hibernate HibernateCriteria: Criteria criteria = session.createCriteria(Book.class); if (startDate != null) { criteria.add(Expression.ge("date",startDate); } if (endDate != null) { criteria.add(Expression.le("date",endDate); } List results = criteria.list();
  • 37.
    37. Transaction inHibernate SELECT * FROM ORDERS WHERE ORDER_ID=’1092’; In Cretira it would become: List orders= session.createCriteria(Order.class) .add(Restrictions.eq(“orderId”,”1092”)) .list(); SELECT O.*, P.* FROM ORDERS O, PRODUCT P WHERE O.ORDER_ID=P.ORDER_ID AND P.ID=’1111’; Would become List orders = session.createCriteria(Order.class) .setFetchMode(“products”,FetchMode.JOIN) .add(Restrictions.eq(“id”,”1111”)) .list();
  • 38.
    38. Transaction inHibernate This criteria query corresponds to the following HQL query: from Book book where book.name = 'Hibernate for Beginners'
  • 39.
    39. Transaction inHibernate •Restriction.between is used to apply a "between" constraint to the field. •Restriction.eq is used to apply an "equal" constraint to the field. •Restriction.ge is used to apply a "greater than or equal" constraint to the field. •Restriction.gt is used to apply a "greater than" constraint to the field. •Restriction.idEq is used to apply an "equal" constraint to the identifier property. •Restriction.in is used to apply an "in" constraint to the field. •Restriction.isNotNull is used to apply an "is not null" constraint to the field. •Restriction.isNull is used to apply an "is null" constraint to the field. •Restriction.ne is used to apply a "not equal" constraint to the field. IN: criteria.add(Restrictions.in("newCourseID", courseIDs));
  • 40.
      7. Caching inHibernate:
  • 41.
    41. Caching inHibernate Hibernate supports the caching of persistent objects at different levels: 1 st level of caching 2 nd Level of caching
  • 42.
    42. Caching inHibernate 1. 1st level of caching:   Suppose we get an object with same identifier for two times within a session, will Hibernate query the database for two times? 
  • 43.
    43. Caching inHibernate If we inspect the SQL statements executed by Hibernate, we will find that only one database query is made. That means Hibernate is caching our objects in the same session. This kind of caching is called “first level caching”, whose caching scope is a session.   But how about getting an object with same identifier for two times in two different sessions?
  • 44.
    44. Caching inHibernate 2 nd Level of caching:
  • 45.
    45. Caching inHibernate  We will find that two database queries are made. That means Hibernate is not caching the persistent objects across different sessions by default. We need to turn on this “second level caching” whose caching scope is a session factory.
  • 46.
    46 Caching inHibernate To enable 2nd level of caching, update the ‘hibernate.cfg.xml’ To monitor the caching activities of Hibernate at runtime, we can add the following line to the log4j configuration file “log4j.properties”. log4j.logger.org.hibernate.cache=debug
  • 47.