Explaining the concept of the data-access object pattern

In the business world, the application always needs to be integrated with the data source in order to read, write, delete, or update data. This data source could be a relational database, NoSQL database, LDAP (Lightweight Directory Access Protocol), or filesystem, for example. Each type of data source has its structure and has a complexity to connect to, read, and write data. These complexities shouldn't be exposed to business logic and instead should be decoupled from it.

The data-access object pattern is a pattern used to abstract and hides all access to data sources from the business tier. This pattern encapsulates all data-source access logic and its complexities from the business tier, decoupling all data-source access logic from it. If we then want to substitute the data source with another, we will only need to modify the code of the data-access object pattern, and this modification will not be visible on the business tier. The...