gdi

Generic Database Interface

This library aims to provide C++11 with a generic interface to manage databases via entity classes, in order to function it is built up based on 4 parts: Entity, EntityManager, Query Builder and Executor.

Entity

Via using the supported macros an entity can be declared as a class that represents a table in the database like:

ENTITY(MyEntity)
ADD(MyEntity, Id, int)
ADD(MyEntity, Number, double)
ADD(MyEntity, Name, std::string)
ADD_VAR(MyEntity, Phone, std::string, 20)
PRIMARY(MyEntity, "Id")
END

After that declaration MyEntity class can be used regularly:

MyEntity entity;
entity.SetId(1);
entity.SetName("MyName");
entity.SetPhone("12345");
entity.SetNumber(3.14);

EntityManager

This class needs an Executor as a dependency. EntityManager manages entity objects and is used to look for, update, insert and delete entities:

• Find(Entity e): This returns an entity from the database which primary key equals e primary key.
• FindBy(Entity e, …): This returns a set of entity objects which have the same e attributes values where … are those attributes names.
• Insert(Entity e): Inserts the entity e into the database.
• Update(Entity e): Updates a row in DB based on the values of e attributes.
• UpdateBy(Entity e, …): Updates DB rows which have same e attributes values where … are those attributes names.
• Delete(Entity e): Deletes a row from the DB based on the primary key.

Query Builder

This builder contains the query to be executed, and it builds queries like:

Select("Country").Count("CustomerID").
        From("Customers").
        GroupBy("Country").
        Having("COUNT(CustomerID)", WhereCondition::GREATER_THAN, "5").
        OrderBy("COUNT(CustomerID) DESC");

Executor

This class is to be implemented for each DBMS differently, here I have written 2 implementations one for MySQL and one for Postgres, it is used to execute the queries and to get the results as entity objects, it should implement 2 methods: Execute and ExecuteQuery.