Java Microservice Layer Architecture
In the WWW you can find a lot about Mircoservice Architecture, but the layer Architecture is usually skipped. This article should serve as an aid by creating a Microservice. The described Architecture is based on my personal experience.
Responsibilities of the individual functionalities are kept separate and modular by a separation of Microservice in 5 layers.
1. Presentation Layer
The presentation layer is only responsible for the interface, it defines the URLs for the endpoints and secures the application. In addition, it forwards requests to the underlying layer, the business layer.
2. Business Layer
The business layer contains the core logic of the system. All algorithms and data processing are performed in this layer. Data required processes are queried from the layer below, the persistence layer.
3. Persistence Layer
The persistence layer has four tasks: reading, storing, deleting and updating data. To hide and unify access to the data sources from business layer, this layer implements a interface for the data from all data sources.
4. Model Layer
The Model Layer encapsulates the data from the communication between external client and presentation layer (data transfer objects — DTOs) and/or between business and presentation layer (business entity — entity)
5. Database Layer
The database layer realized the basis of the data interface of the services, the database.
Please note that database layer is physically outsourced!
Package Structure
The Layer architecture consider the high level layers of the complete software architecture of the services and their tasks. The structure of the four upper layers (presentation, business, persistence and model), which are in the source code of the application, is described in the package structure.
The database layer is not considered there!
1. Controller Package
Controller Package is responsible for the endpoints (REST controller).
2. Service Package
Service Package contains all algorithms and business logic for data processing.
3. Repository Package
Repository Package processes and collects data from the various data sources.
4. Model Package
Model Package includes business, transfer data models and mapper between them.
4.1 DTO
Data Transfer Object is an abstract model object that organizes response and request model standardizes.
4.1.1/4.1.2 Response/Request Sub-Package
Represents data transfer model that are processed or responses by the application. Response/Request inherits the structure from the Model DTO class.
4.2 Entity
Entity is a lightweight persistence domain object
4.3 Mapper
Mapper represents map generator between object models (entities and DTOs).
5. Config Package
Config Package indicates @Bean methods and processed by the Java container to generate bean definitions and service requests for those beans at runtime.
6. Common Package
Common package includes helper and util classes, interfaces and methods that could be used in entire microsevice.
6.1 Internal Sub-Package
Internal Package contains the implementation for the internal communications between the application services.
6.2 External Sub-Package
External Package contains the implementation for the external communications of the 3rd party services.
6.3 Exception Sub-Package
Exception Package contains the exception handling for the service.
6.4 Util Sub-Package
Util includes general helper methods and classes.
