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Learning NHibernate 4

Book Image

Learning NHibernate 4

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Learning NHibernate 4
Jul, 2015 | 402 pages
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Table of Contents (18 chapters)
Learning NHibernate 4
Learning NHibernate 4
Credits
Credits
About the Author
About the Author
About the Reviewers
About the Reviewers
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Introduction to NHibernate
Introduction to NHibernate
What is ORM?
What is NHibernate?
What is new in NHibernate 4.0?
NHibernate for users of Entity Framework
Is using ORM a bad idea?
Building blocks of NHibernate
Summary
2
Let's Build a Simple Application
Let's Build a Simple Application
Explaining the approach used in learning NHibernate
The problem statement
The development setup
The domain model
Adding some code
Summary
3
Let's Tell NHibernate About Our Database
Let's Tell NHibernate About Our Database
Important NHibernate terminology
Mapping the prerequisites
Different mechanisms to write the mappings
XML mappings for the Employee class
Identifier generation
Mapping associations
Mapping inheritance
Mapping components
Mapping by code
Fluent mapping a.k.a. Fluent NHibernate
Choosing the right mapping method
Summary
4
NHibernate Warm-up
NHibernate Warm-up
Warming up NHibernate succinctly
The NHibernate session architecture
XML configuration
Programmatic configuration
Loquacious configuration
Fluent configuration
Configuration options
Generating the database scripts from mappings
Summary
5
Let's Store Some Data into the Database
Let's Store Some Data into the Database
Entity states
Transactions and unit of work
Saving entities
Transitive persistence using cascade styles
Transitive persistence/cascading in action
Bidirectional associations and ownership
Order of operations
Entity equality
The architecture diagram
Summary
6
Let's Retrieve Some Data from the Database
Let's Retrieve Some Data from the Database
Querying the workflow
Different querying methods
Joins
Lazy loading
Eager fetching
Pagination and ordering of results
Retrieving entities by identifiers
Polymorphic queries
Summary
7
Optimizing the Data Access Layer
Optimizing the Data Access Layer
Baseline and optimize
Organization of the chapter
Batching
Fetching strategies

Avoiding the select N+1 problem
Avoiding eager fetching
Using extra-lazy for lazy collections
Summary
8
Using NHibernate in a Real-world Application
Using NHibernate in a Real-world Application
What kind of application are we building?
Architectural principles we will follow
Feature 1 – onboarding an employee
Unit of work
Feature 2 – updating the details of an employee
Feature 3 – searching employees
Summary
9
Advanced Data Access Patterns
Advanced Data Access Patterns
Problems with the repository pattern
Specification pattern
Query object pattern
Summary
10
Working with Legacy Database
Working with Legacy Database
Composite IDs
Components
Join-mapping to load data from multiple tables
Working with database views
Using subselect instead of views
Working with stored procedures
Using custom DTOs
Summary
11
A Whirlwind Tour of Other NHibernate Features
A Whirlwind Tour of Other NHibernate Features
Concurrency control
Event system
Caching
Stateless sessions
User-defined types
Summary
Index
Index

What is new in NHibernate 4.0?

The General Availability release of NHibernate 4.0.3.400 was released on August 17 2014. This is the latest release of NHibernate as of the time of writing of this book. This release is quite important from a lot of perspectives. This is a major release of NHibernate that has come almost after three and a half years, so it contains a lot of interesting features and bug fixes.

If you are new to the ORM land or have never used NHibernate before, then you may not find this section very interesting. But hey, why not keep reading and you might find something that strikes a chord with you:

  • NH 4.0 is built for .NET 4.0. This may not mean much for the users of NHibernate 4.0 as you can still use older versions of NHibernate on a project that is built on .NET 4.0. However, this is a major move for NHibernate since it now gives NHibernate developers the ability to utilize new features of .NET 4.0. An immediate consequence of this was that NHibernate 4.0 now does not depend on the Iesi.Collection library to support sets (Iesi.Collections.Generic.ISet<T>) because .NET 4.0 has native support for sets, in the form of ISet<T>, and implementations such as HashSet<T>. Back in the days when the old versions of .NET did not have support for sets, the Iesi.Collections library offered a mature set functionality. NHibernate had a dependency on this external library as NHibernate uses sets to represent collections.

  • Support for SQL Server 2012 has improved with the implementation of the native IIF function, query paging, and SQL Server 2012 sequences.

  • "Mapping by code" rids you of having to write and maintain cumbersome XML mapping files. However, the general audience was never happy with this feature as it was buggy till recent times. NHibernate 4.0 has several defects in this area fixed, thus giving Mapping by code a facelift.

  • We all love LINQ and we all hated the fact that NH's LINQ support never matched that of Criteria or QueryOver. There has been great community contribution in this area with over 140 issues fixed. LINQ support in NHibernate 4.0 has matched that of other query providers in a lot of respects. We will be using this feature a lot in the coming chapters of this book.

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