The Data Source Layer patterns introduced in lecture L08 are structural patterns. They deal with moving data to and from the database. They try to solve the impedance mismatch problem. However, they do not have any logic as to when and under what circumstances data should be loaded to from the database and when written. Clearly accessing the database is slow, and doing so needlessly hurts performance.
In this lecture we look at the behavioural problem. How to solve issues like writing only changed record back into the database, loading only the needed data once, and how to load the data model partially.
We introduce three new design patterns: Unit of Work, Identity Map and Lazy Load.
Slides:
Video, Part 1:
Video, Part 2:
Video, Part 3: