在业务或数据层中编写逻辑

Question

I am using a three layered architecture in my web application. I am writing all the MS SQL Server database related codes in the Data Layer and now there is a requirement to read lots of data from Excel, CSV and other spreadsheet files. I am using the OleDbConnection, OleDbCommand, OleDbDataReader to read all the contents from the spreadsheet files that are uploaded by the user. There is a debate regarding where I should write the required code, In the Business Logic layer or Data Layer? My assumption is like since reading from the spreadsheet does not have anything to do with our MS SQL Server Db and so I thought of writing it in the Business Logic Layer.

Is it a right decision? Any thoughts?

Answer 1

Data Layer. Actually it's still a data stream. You should treat it as such Your business layer, normally, should not even know from where data comes.

Answer 2

I would rather why don't you build multiple projects in the solution for a united Data Access Layer. Theoretically you will still be designing a three-tier architecture, but with code disparity for high manageability and scalability. Here's how the architecture tree look like:

1. Application Logic [Presentation Layer]
2. Business Logic Layer
3. Data Access Layer [Abstract Layer for communication with BL]
   • SQL Server DAL
   • Excel DAL
   • Access DAL
   • any other DAL...

I'm sure this would work fine with your architecture.

Answer 3

Best option to extract or save data from any source is to implement it in data layer. Then pass this data to business layer to apply business logic/business rules. Keep data access & storage transparent to business layer.

Some of the benefits: 1. This is to decouple the future scalability & extensibility. If you need to change excel data source to a RDBMS or any other type of file then you don't need to change any business logic. Only data access logic would be changed. Similarly if you need to add more business rules or remove some then you don't need to change the data access layer. 2. If you need to merge data from tow data sources then you can do it easily transparent to business layer