Lars-Erik Kindblad presentation at the Capgemini Microsoft User Group 2012.

1. Data Access – Best Practice
Lars-Erik Kindblad
Senior Consultant
Blog: kindblad.com

2. Agenda
 Why is Data Access so important?
 Common issues in many applications
 How to solve these issues
 Summary
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3. Why is Data Access so important?
 Retrieving, creating, updating and deleting data are core operations
 Affects the entire application in a bad way if done incorrectly
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4. Common issues in many applications
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5. Code issues
 The code in the data access layer is often put into a single or a few
huge classes
• Hard to maintain
 Database queries are constructed in the frontend or business layer
• Leads to messy frontend or business code
 ORM framework limitations or lack of «ORM masters»
• A lot of quickfixes
 Doesn’t support rollback of changes when errors occurs
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6. Performance issues
 The application slow
• Too many database queries
• Too heavy database queries
• Lazy loading
• Poorly generated SQL by the ORM framework
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7. Security issues
 Vulnerable to SQL Injection
 Users get access to data they should not have access too
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8. Quality issues
 Many bugs
• No tests
• ... or tests that doesn’t test the important stuff
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9. How to solve these issues
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10. What do we want?
 Well structured data access code that is easy to maintain
• Small simple classes that does only one thing - Single Responsiblity Principle
 The application should be fast
• Only retrieve the data that we actually need – Criteria Pattern
• Do as much as possible in one query – SQL Joins
• Avoid lazy loading
 The application should be secure
• Use an ORM framework and/or use parameters instead of concatenated strings
• Always check for permissions when retrieving, creating, updating or deleting data
 Rollback uncomitted changes if anything goes wrong
• Transaction support
 As little dependency on the ORM as possible
• Gateway Pattern
 Frontend, Business and Data Access Code should be separated
• Logical Layering
 High quality – Bug free code
• Integration tests
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11. Example code
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12. HOW TO:
REDUCE ORM DEPENDENCIES
STRICTER LAYERING
ROLLBACK IF ERROR OCCURS
HAVE SIMPLE DATA ACCESS CODE
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13. The Common Way
Frontend
Layer
Business
ORM
Layer
Query the Database
Data Access
Layer
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14. A Better Way
Frontend
Layer
ORM
Gateway
Initialize ORM Business
Transaction management Layer
ORM
Data Access
Layer
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15. DbContexGateway for FluentData
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16. Data Access Layer
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17. Business Layer
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18. Frontend Layer
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19. EFFICIENT DATA RETRIEVAL & FILTERING
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20. Overview
Frontend Criteria Pattern: Decide what data to retrieve and filter on
Class
Business Business logic
Class
Data Access
Class Construct the most optimal and secure query
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21. Frontend Layer
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22. Business Layer
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23. Data Access Layer
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24. Overview
Frontend Transaction management
Layer Decide what data to retrieve and filter on
Business Business logic
Layer
Data Access
Layer Construct the most optimal and secure query
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25. HOW TO:
GET A HIGH QUALITY APPLICATION
THROUGH INTEGRATION TESTS
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26. Test - CreateProductDbCommand
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27. Test - GetProductsDbCommand
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28. Summary
 Have small simple classes that does only one thing
 Use the Criteria Pattern to decide what data to retrieve
 Use joins to retrieve as much data as needed in one query
 Avoid lazy loading
 Use parameters instead of concatenated strings
 Always check for permissions when retrieving, creating, updating or
deleting data
 Use transactions to rollback when errors occurs
 Use the Gateway Pattern to reduce ORM dependency
 Have a strict Frontend layer, Business layer, Data Access layer
 Verify quality through Integration Tests
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29. QUESTIONS?
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30. www.capgemini.com
The information contained in this presentation is proprietary. ©2010 Capgemini. All rights reserved