What is the difference between DAO and DAL?

dao data-access-layer data-access-object
simoraman picture simoraman · Jul 6, 2009 · Viewed 31.8k times · Source

Having studied Java at school I am quite familiar with the DAO-pattern(Data access object). However at work I use .NET. In .NET there is often talk about the DAL(Data Access Layer). To me their purpose seems quite similar. So the question is are DAO and DAL basically the same thing? Is the term DAL only made up so it wouldn't be mixed up with Data Access Objects?

Answer

Matt Howells picture Matt Howells · Jul 6, 2009

The Data Access Layer (DAL) is the layer of a system that exists between the business logic layer and the persistence / storage layer. A DAL might be a single class, or it might be composed of multiple Data Access Objects (DAOs). It may have a facade over the top for the business layer to talk to, hiding the complexity of the data access logic. It might be a third-party object-relational mapping tool (ORM) such as Hibernate.

DAL is an architectural term, DAOs are a design detail.

Related questions

Why put a DAO layer over a persistence layer (like JDO or Hibernate)

Data Access Objects (DAOs) are a common design pattern, and recommended by Sun. But the earliest examples of Java DAOs interacted directly with relational databases -- they were, in essence, doing object-relational mapping (ORM). Nowadays, I see DAOs on top …

Read More
Design Patterns for Data Access Layer

I have an application which uses a database (MongoDB) to store information. In the past I have used a class full of static methods to save and retrieve data but I have since realised this is not very object-oriented-ish or …

Read More
What is the difference between DAL, DTO and DAO in a 3 tier architecture style including with MVC

Recently I was learning about ORM (Object Relational Mapping) and the 3 tier architecture style (presentation,business and data persistence). If I understand correctly, I can separate the data persistence layer into DTO and DAO layer. I would like to understand, …

Read More