Exploring design patterns with MongoDB TAMING THE HORSEPOWERS Morten Holk Maate Sr. Developer, Product Manager mhm@configit.com

db.GetCollection(''Employee'').Save(employee);

One reason that MongoDB is great is that our data store uses objects – as well as our OO programming language uses objects JSON in Mongo Shell: C# in Visual Studio:

… and objects do seem like a great abstraction for … objects

MongoDB Solves The Object-Relational Impedence Mismatch • Data Mapping • Normalization • Object Identity • Serialization Storing Objects as Objects Utilizing Object Hierarkies With ObjectId() As BSON

Your Object is not your Object! Is NOT equal to this: And this:

Literally 

EXPECTATIONS • Data Mapping • Normalization • Object Identity • Serialization REALITY • C#/Java objects still needs some mapping to become Mongo Objects • C#/Java objects still needs some normalization • We have not solved the identity problem • Serialization still is not easy

Hands on case: Storing employees in a database Take 1 Illustrating the Challenges

Main Procedure • Create object instance • Store object • Load object SalesEmployee + Id : ObjectId + Name : String + Value : Int32 Mongo DB

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db.GetCollection(''Employee'').Save(employee); Won’t build without MongoDB Reference

Won’t build without MongoDB Reference

Hands on case: Storing employees in a database Take 2 ”ActiveRecord Pattern”

Main Procedure • Create object instance • Store object • Load object SalesEmployee + Id : ObjectId + Name : String + Value : Int32 + Save() + Load() Mongo DB Active Record I

Main Procedure • Create object instance • Store object • Load object PersistentObject + ObjectId + void Save(T obj) + T Load(ObjectId id) SalesEmployee + Name : String + Value : Int32 Mongo DB DataAccess Domain Active Record II

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Hands on case: Storing employees in a database Take 3 ”Repository Pattern”

Main Procedure • Create object instance • Store object • Load object Employee + Name : String + Value : Int32 Repository + void Save(T obj) + T Load(ObjectId id) IRepository + Load() + Save() Sales Employee Developer Mongo DB DataAccess Domain Repository Pattern PersistentObject + ObjectId

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Hands on case: Storing employees in a database Take 4 ”DataMapper pattern”

Main Procedure • Map Data • Create object instance • Store object • Load object Employee + Id : String + Name : String + Value : Int32 Repository + void Save(T obj) + T Load(String id) IRepository + Load() + Save() Sales Employee Developer Mongo DB DataAccess Domain Settings + SetupDatabase() DataMapping DataMapper

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Hands on case: Storing employees in a database Take 5 ”DataMapper pattern II”

Main Procedure • Create object instance • Store object • Load object Employee + Id : String + Name : String + Value : Int32 Repository + void Save(T obj) + T Load(String id) Employee Repository IRepository + Load() + Save() Sales Employee Developer +BestFriend : Developer Developer Repository Developer Repository Mongo DB DataAccess Domain DataMapper Pattern

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