Mastering Layered Java Architecture: Clear Business Logic & Clean Code

Alibaba's Java framework adopts a multi‑layered architecture that clarifies business responsibilities and improves code cleanliness.

Application layers include:

Open API layer : Exposes services as RPC or HTTP interfaces, and can be accessed by the gateway control layer.

Terminal display layer : Handles template rendering for various clients (Velocity, JS, JSP, mobile, etc.).

Web layer : Performs request routing, basic parameter validation, and simple non‑reusable business processing.

Service layer : Contains specific business‑logic services.

Manager layer : Provides generic business handling, such as third‑party platform wrappers, cache or middleware utilities, and interacts with the DAO layer for common data operations.

DAO layer : Manages data access to MySQL, Oracle, HBase, or OB, and interfaces with external RPC/HTTP services.

Exception handling guidelines suggest catching generic Exception in the DAO layer, wrapping it in a DaoException, and logging at the Service or Manager layer to avoid duplicate logging and performance loss. The Web layer should not re‑throw exceptions; instead, it should direct users to friendly error pages, while the Open API layer returns standardized error codes and messages.

Domain model conventions define several object types:

DO (Data Object) : Mirrors database tables and is transferred via the DAO layer.

DTO (Data Transfer Object) : Used by Service and Manager layers for external communication.

BO (Business Object) : Encapsulates business logic output from the Service layer.

QUERY : Represents query parameters; queries with more than two parameters must avoid using generic Map objects.

VO (View Object) : Delivered from the Web layer to the template rendering engine.