Object-relational mapping

Author: Jaroslav OrságDiploma thesis supervisor: Ing. Augustín Mrázik

Goal of Thesis

• Analysis of OOP principles, which should be supported by ORM frameworks

• Analyze some of the most important ORM frameworks (free, commercial)

• Compare reviewed frameworks

Brief qualified overview of ORM for developers and IT managers

Contents

• The Problem

• Kinds of Cooperation

• Patterns

• Analisis of Frameworks– Frameworks– Criteria

• Conclusion

The Problem (1)OOP

• Encapsulation

• Inheritance

• Polymorphism

• Class, Instance

The Problem (2)RDBMS

• Tables

• Views

• Stored Procedures

• Relations

The Problem (3)

• 2 different worlds (different paradigms)• Different data representation• Different data manipulation• Different modeling techniques• Semantic gap• Impedance mismatch• Problem appears in huge software

projects with lots of entities

The Problem (4)Typical EIS• Typical architecture of

today’s information system

Kinds of cooperation (1)

• HTML + ASP + MS SQL (Example 1)– SQL statements in ASP(JScript, VB) code– Working with tuples (records) in ASP

environment– Code is ugly– Sufficient for small projects

Kinds of cooperation (2)

• .NET + MS SQL (Example 2)– Instruments for more sophisticated data

manipulation (.net DataSets, DataTables)– It is possible (more simple) to create kind of

own specific mapper– This mapper is not reusable– Java + JDBC + Oracle

Kinds of cooperation (3)

• .NET + ORM + MS SQL (Example 3)– Reusable ORM mapper is used– Object model is created and appropriate

relational model is created and maintained by mapper

Mapping Approaches

• Do It Yourself (Example 1 & 2)• Free or commercial software (Example 2 & 3)• Approaches used by 3rd party tools (mappers)

– Entity approach • Data are just data - use of objects without behavior• Special classes for changing state of objects (objects are

parameters of static methods of so-called management classes)• Since ’70-ies

– Domain model approach• No management classes• Persistent objects contains behavior• Possible use of polymorphism to override behavior• True ORM mappers

Patterns (1)

• Mapping of inheritance– One inheritance tree – one table

Patterns (2)

• Mapping of inheritance– One class – one table

Patterns (3)

• Mapping of inheritance– One concrete class – one table

Patterns (4)

• Mapping of inheritance– Generic table structure

Patterns (5)

• Mapping of aggregation– Single table

aggregation

Patterns (6)

• Mapping of aggregation– Foreign key aggregation

Performance

• Caching

• Lazy loading

• Delayed updates

Configuration

• Attribute-oriented programming

• Configuration files

Analysis of Frameworks

• DataObjects.NET

• Hibernate

• TopLink

• LLBLGenPro

• Java Data Object (JDO)

Analysis Aspects

• Architecture• Criteria

– Transparency– Documentation & support– Dependencies, supported platforms, portability– Maintainability of model– Usability– Configuration vs. automation– Constraints on design of object model

Framework Overview

Conclusion

• Work brings orientation within given topic and can serve as a guide when deciding which framework to use

• Evaluation presented in this work cannot be considered to be general for any purpose / problem ("one size fits all...")

• Different frameworks are designed for different situations

• Results of this work can serve as a guide for evaluation of frameworks for a particular development project

Odpovede (1)

• Kompilačná práca

Odpovede (2)

• “Autor vychádza najmä z troch prác, pričom štruktúra textu (kapitoly a podkapitoly) spracovaného textu nápadne pripominajú jeden z citovaných zdrojov.”

Odpovede (3)

• “Kvalita grafického spracovania príkladov/obrázkov nezodpovedá zvyšku práce, a v čitateľovi podobne vzbudzuje pochybnosti o ich pôvode.”

Odpovede (4)

• Porovnanie frameworkov a kritériá

Odpovede (5)

• Anglický jazyk

Odpovede (6)

• Použitá literatúra, zdroje

Questions

• …