Table of Contents

Data Access Layer

The Data Access Layer (DAL) handles all interactions between an application and the underlying data storage system. It acts as an intermediary, shielding the rest of the application from the complexities of data access.

The key responsibilities of Data Access Layer is to retriev data from the database based on specific criteria (e.g., queries, filters). Transforms raw data from the database into objects that the application can understand.

Data Access Layer implementation

Data access type

  • Raw database table data
  • Object

The Data Access Layer can retrieve or save objects from the database, or it can be implemented to access raw database table data.

  • An object is an entity that has state, behavior, and identity.
Feature Object-oriented Data-oriented
Abstraction Level High Lower
Focus Object-relational mapping Row-level operations
Complexity Generally more complex Simpler to implement

Patterns

  • Gateway

    • Data oriented

      • Row Gateway
      • Table Gateway
      • Data Acceess Object

    • Object oriented

      • Data Mapper
      • Repository
      • Data Acceess Object

  • Active Record

    • Object-oriented
      • Active Record

The Data Access Layer can be implemented using either the Gateway pattern or the Active Record pattern.

Gateway

The Gateway is a pattern that centralizes and controls interactions with external systems or subsystems.
It isolates clients from the complexities of directly interacting with external systems by providing simplified interface to interact with.

In essence, the Gateway pattern aims to create a more maintainable and efficient interaction between clients and external systems.

Examples

API Gateway In microservices architecture, it acts as a single entry point for clients to access multiple microservices.

Database Gateway Encapsulates all database access logic for a specific table or set of tables.

Third-party API Gateway Acts as an intermediary between the application and external APIs (e.g., image Service, payment Service)

Active Record

The Active Record pattern is a software design pattern that integrates both business logic and data persistence within a single object.

Where each object in the system directly corresponds to a row in a database table.

Edit this page