O/RM - Introduction. Christian Horsdal Gammelgaard

Transcription

1 O/RM - Introduction Christian Horsdal Gammelgaard

2 Content First half: Introduction to O/R Mapping Second half: NHibernate demo 1

3 Who am I? Christian Horsdal Gammelgaard Lead Software Architect, Mjølner Informatics M.Sc. DAIMI,

4 Contents First Half Object/Relational Mapping Intro Impedance Mismatch O/RM Patterns Hibernate Quick Intro 3

5 4 Object/Relational Mapping

6 5 Object/Relational Mapping

7 Contents First Half Object/Relational Mapping Intro Impedance Mismatch O/RM Patterns Hibernate Quick Intro 6

8 7 Impedance Mismatch

9 Impedance Mismatch Identity All objects are unique Each one has an identity May contain equal data Tables are sets of rows No unique identity per se May not contain equal data Primary key is often an ID 8

10 Impedance Mismatch Structure - relationships Orders Order_Id Account_ID Order_Date Order_ShipToFirstName Order_ShipToLastName Order_ShipAddr1 Order_ShipAddr2 Order_ShipCity Order_ShipState Order_ShipZip Order_ShipCountry LinesItem Order_Id LineItem_LineNum Item_Id LineItem_Quantity LineItem_UnitPrice 9

11 Impedance Mismatch Inheritance In the OO world LSP Abstract classes Concrete classes In the relational world Tables w/o inheritance 10

12 Impedance Mismatch and the list goes on Constraints Transactions Partial rows vs. partial objects 11

13 Contents First Half Object/Relational Mapping Intro Impedance Mismatch O/RM Patterns Hibernate Quick Intro 12

14 O/RM Patterns Row Data Gateway Active Record Relationship: One to One One to Many Many to Many Inheritance Unit of Work 13

15 O/RM Patterns Row Data Gateway An object that acts as a Gateway, to a single record in a data source. There is one instance per row. -- Martin Fowler, PoEAA 14

16 O/RM Patterns Active Record An object carries both data and behavior. Much of this data is persistent and needs to be stored in a database. Active Record uses the most obvious approach, putting data access logic in the domain object. -- Martin Fowler, PoEAA 15

17 O/RM Patterns Relationship One to One Orders Order_Id Account_ID Order_Date Order_ShipToFirst... Order_ShipToLast... Order_ShipAddr1 Order_ShipAddr2 Order_ShipCity Order_ShipState Order_ShipZip Order_ShipCountry Order_BillToFirstN... Order_BillToLastN... Accounts Account_Id Account_ Account_FirstName Account_LastName Account_Status Account_Addr1 Account_Addr2 Account_City Account_State Account_Zip Account_Country Account_Phone 16

18 O/RM Patterns Relationship One to Many Orders Order_Id Account_ID Order_Date Order_ShipToFirstName Order_ShipToLastName Order_ShipAddr1 Order_ShipAddr2 Order_ShipCity Order_ShipState Order_ShipZip Order_ShipCountry LinesItem Order_Id LineItem_LineNum Item_Id LineItem_Quantity LineItem_UnitPrice 17

19 O/RM Patterns Relationship Many to Many Product Id ProductId Name Description ProductCategory * productid categroyid Category Id CategoryId Name Description 18

20 O/RM Patterns Inheritance Single Table Cards address owner creditlimit balance class 19

21 O/RM Patterns Inheritance Concrete Class Table DebitCards address owner balance CreditCards address owner creditlimit 20

22 O/RM Patterns Unit of Work Maintains a list of objects affected by a business transaction and coordinates the writing out of changes and the resolution of concurrency problems -- Martin Fowler, PoEAA 21

23 O/RM Patterns Unit of Work application database unit of work new order select RegisterClean AddLineItem RegisterDirty Commit Save Update 22

24 23 O/RM Patterns Unit of Work Hibernate Session

25 Contents First Half Object/Relational Mapping Intro Impedance Mismatch O/RM Patterns NHibernate Quick Intro 24

26 NHibernate Overview O/RM written in C# Works well with most CLR languages C#, VB.NET, IronRuby, IronPython, F# Works with all major RDBMSs Oracle, DB2, MySql, MS SQL Server, SyBase, PostgreSQL And a lot of minor ones: SQLite, H2, MS Access, FireBird And even some weird ones: flat text files, MS Excel (!), 25

27 26 NHibernate overview

28 Contents First Half Object/Relational Mapping Intro Impedance Mismatch O/RM Patterns Hibernate Quick Intro 27

29 Content First half: Introduction to O/R Mapping Second half: Hibernate demo 28

30 References Martin Fowler: Patterns of Enterprise Application Architecture Christian Bauer, Gavin King: Java Persistence with Hibernate NHibernate home: Fluent Nhibernate: Blog: horsdal.blogspot.com Mjølner: Contact Information 29