Detailed examples of Java design pattern (DAO)

Detailed examples of Java design pattern (DAO)

Application scenario: in Java programs, it is often necessary to persist data and obtain persistent data, but there are many problems in the process of data persistence (such as different data sources, different storage types, different suppliers, different access methods, etc.). How can data persistence be operated with a unified interface?

In fact, I don't have a student number (R n q). My understanding is that a product is not aimed at a single user, so we should be compatible with many situations, such as different data sources, different storage types, different suppliers, different access methods, etc.

★ solution

Understanding of Dao:

1. Dao actually uses the combined factory model to solve problems, and does not bring new functions, so learning is actually an idea. 2. Theoretically, there is no limit on the number of layers of Dao. 3. Theoretically, there is no sequence of layers of Dao.

There are three types of project files:

Some code implementation

Interface

Factory method (multiple alternative implementations)

There are several factories with similar methods, so they don't post them

Implementation class

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