问题
What's the difference between a Data Access Object and Active Record? They seem to be quite the same, as both built a layer between the application and persistence layer, and abstract away direct database access using SQL queries.
回答1:
Data Access Object (DAO) refers to an object in your data layer responsible for persisting a separate entity in your domain. Active Record is a specific method of doing a DAO where the class containing the values of a single row from a table is also responsible for queries, updates, inserts, and deletes to that table. The Active Record design pattern means your object has a one-to-one mapping with a table in your database.
回答2:
A Data Access Object (DAO) is an interface dedicated to the persistence of a model/domain object to a data-source. Here's a reference.
The ActiveRecord pattern works in a similar fashion, but puts the persistence methods on the model object itself, while the DAO defines a discrete interface.
The advantage of the DAO pattern is:
Its easy to define another style of persistence, eg moving from a Database to cloud, without changing the underlying impelementation, while the external interface remains the same, therefore not affecting other classes.
The persistence concerns are modularized away from the main model object concerns.
The advantage of the ActiveRecord pattern is simplicity.
来源：https://stackoverflow.com/questions/6640784/difference-between-active-record-and-dao