The pet store application

Computer programming books often start with the Hello World application. Similarly, books describing a framework often develop a pet store application. We will follow this tradition. The pet store that we will develop will be a simple application that will allow you to browse the catalog of pets, add some of them to your cart, and finalize the payment.

During the development of the application, we will be concentrating on cloud and microservice aspects. The service code is simple and uses basic Java EE technologies so that the reader can concentrate on what is being taught in this book: cloud integration and microservices development.

Let's take the bird's-eye view of the application:

The backend services (red), gateways (yellow), and security server (blue) are deployed in a cloud. The UI application (green) is deployed outside the cloud.

The gateway services are responsible for providing APIs for different users. The customer gateway provides an API for customers, which is used by petstore-ui—web-client implementing the store interface. The customer gateway orchestrates invocations to the underlying base services and is accessible from outside the cloud.

The security service is responsible for the authentication and authorization of access to different parts of the API. It is used by all other components. The security service is accessible from outside the cloud.

The core functionalities are implemented by backend services. Backend services are not accessible from the gateway service. Let's take a look at their functions:

• Catalog service: Provides information about pets available in the store
• Pricing service: Responsible for providing the price of a given pet
• Cart service: Responsible for keeping information about the cart of a given customer

We will develop the application step by step throughout the book. The application is attached to the book, and as a result, you could work with it immediately while learning various concepts described in the book.