Application Layering Best Practices and Alibaba Specification

Background: Many developers misunderstand application layering, mixing responsibilities among controller, service, and mapper, which leads to maintenance difficulties and poor code reuse.

A good application layering should facilitate future maintenance and extension, be accepted by the whole team, and have clearly defined responsibilities for each layer.

Alibaba's coding specification defines clear layers:

Open Interface Layer – wraps Service methods as RPC or HTTP interfaces with gateway security and traffic control.

Presentation Layer – renders templates for various clients (Velocity, JS, JSP, mobile).

Web Layer – handles access control, basic parameter validation, and simple business processing.

Service Layer – contains specific business logic.

Manager Layer – provides reusable logic such as third‑party integrations, caching, middleware handling, and aggregates DAO interactions.

DAO Layer – data access, interacting with MySQL, Oracle, HBase, etc.

Optimized layering adds a TService (RPC) layer similar to a controller and emphasizes keeping business orchestration in the Service layer, reusable logic in the Manager layer, and restricting DAO access to Service/Manager only.

Domain model conversion in Alibaba's guidelines includes:

DO (Data Object) – mirrors database tables.

DTO (Data Transfer Object) – used for data transfer from Service/Manager.

BO (Business Object) – encapsulates business logic output.

AO (Application Object) – near the presentation layer, low reuse.

VO (View Object) – passed to rendering engines.

Query – encapsulates query parameters, avoiding Map for >2 parameters.

Excessive conversions across layers can cause performance overhead; a balanced approach allows Service/Manager to work directly with domain models while preventing DAO objects from flowing up to controllers.

Conclusion: Proper layering is crucial for code standards, reusability, and clear responsibilities; while teams may have different habits, the essential goal is clear logical boundaries that simplify maintenance and future development.