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...
