NHibernate

1
nhibernate

• Meysam Roostaee
• Mohammad Ali Bahrami

2
Agenda

• Introduction to ORM
• Introduction to Nhibernate
• Nhibernate in Action

3
Introduction to ORM

• What is ORM?
• ORM Benefits
• ORM and Architacture

4
What is ORM?

• Object-relational mapping (aka ORM, O/RM, and O/R
  mapping) is a programming technique for
  converting data between incompatible type systems
  in relational databases and object-oriented
  programming languages (Wikipedia)
• Objects are hierarchical
• Databases are relational

5
Orm benefits

• Productivity
• Eliminates lots of repetitive code focus on
  business logic
• Maintainability
• Fewer lines of code easier to understand
• Easier to manage change in the object model
• Performance
• Lazy loading associations are fetched when
  needed
• Caching
• Database vendor independence
• The underlying database is abstracted away
• Can be configured outside the application

6
ORM and Architecture
Call data access layer
MySQl, Oracle, SQL Server, etc.
7
Introduction to Nhibernate

• Key features
• High level architecture
• Very important concept
• Access persistent object
• Nhibernate in a nutshell
• Hibernate-config.xml

8
Key features

• NHibernate is a port of Hibernate Core for Java
  to the .NET Framework
• Natural programming model
• NHibernate supports natural OO idiom
  inheritance, polymorphism, specialization and the
  .NET collections framework
• Support for fine-grained object models
• A rich variety of mappings for collections and
  dependent objects

9
Key features

• The query options
• NHibernate addresses both sides of the problem
  not only how to get objects into the database,
  but also how to get them out again.
• Query API with HQL (Hibernate query language)
• HQL is fully object-oriented, understanding
  notions like inheritence, polymorphism and
  joins.
• example
• select cat.Mate from Eg.Cat as cat
• -The query will select Mates of other Cats.
  Actually, you may express this query by join
• select mate from Eg.Cat as cat inner join
  cat.Mate as mate

10
Key features

• Native SQL
• Execution of native SQL queries is
  controlled via ISQLQuery  interface,
  
  which is obtained by calling
  ISession.CreateSQLQuery().
• example 1 Scalar queries
• sess.CreateSQLQuery("SELECT FROM
  CATS") .AddScalar("ID", NHibernateUtil.Int64)
  .AddScalar("NAME", NHibernateUtil.String) .AddSc
  alar("BIRTHDATE", NHibernateUtil.Date)
• the columns and types to return.
• example 2 Entity queries
• Query query sess.CreateSQLQuery("SELECT ID,
  NAME, BIRTHDATE FROM
  CATS ").AddEntity(typeof(Cat))
• List result query.list()
• the entity returned by the query.
• Assuming that Cat is mapped as a class with the
  columns ID, NAME and BIRTHDATE the above queries
  will both return an IList where each element is
  a Cat entity.

11
Key features

• Custom SQL
• Include stored procedures are supported on
  Microsoft SQL Server
• All popular databases supported
• Oracle, SQL Server, DB2, SQLite, PostgreSQL,
  MySQL, Sybase, etc.
• XML-based configuration files
• Good community support (http//www.nhforge.org)
• Free/open source
• NHibernate is licensed under the LGPL (Lesser GNU
  Public License)

12
High level architecture
13
Very important concept
14
Access persistent object

• Configuration
• Used to configure Nhibernate
• Specify the location of mapping documents
• ISessionFactory
• The application obtains ISession instances from
  an ISessionFactory
• One per database (or application)
• The SessionFactory caches generated SQL
  statements and other mapping metadata that
  NHibernate uses at runtime

15
Access persistent object

• ISession
• The primary interface used by NHibernate
  applications
• Finding, saving,retrieving,updating, and deleting
  objects
• Call the ISession a persistence manager
• Itransaction
• Encapsulates database transactions (abstracts
  application code from the underlying transaction
  implementation)
• All communication with a database has to occur
  inside a transaction Should end either with a
  commit or a rollback
• IQUERY
• Gives you powerful ways to perform queries
  against the database while also controlling how
  the query is executed.
• Basic interface used for fetching data using
  NHibernate.
• Queries are written in HQL or in your databases
  native SQL dialect

16
Nhibernate in a nutshell

• Configuration Class builds Session Factory
• Session Factory builds Session
• Session is used as Unit Of Work to interaction
  with objects
• --------------------------------------------------
  --------------------------------
• Configuration config new Configuration()
  .Configure()
• var sessionFactorynew config.BuildSessionFactory
  ()
• using (var sessionsessionFactory.openSession())
• var customernew Customer()
• session.SaveOrUpdate(customer)
• session.Flush()

17
Hibernate-config.xml
18
(No Transcript)
19
To be continued
20
(No Transcript)
21
References

• http//www.nhforge.org/doc/nh/en/index.html
• http//fluentnhibernate.org
• http//en.wikipedia.org/wiki/Nhibernate
• http//www.dotnetspider.com
• http//www.summerofnhibernate.com/
• http//en.wikipedia.org/wiki/Object-Relational_Map
  ping
• NHibernate in Action --PIERRE HENRI KUATÉ, TOBIN
  HARRIS.
• NHibernate explained by example -- Dragos Nuta,
  2005 .