# Sample Application Architecture

## Architecture

As part of this workshop we will implement the following sample application architecture.

![Architecture](/files/7hnewp15bVotSgsrgdTB)

We will use the provided existing two microservices (customer and product services) to route these through the Spring Cloud Gateway.

* **Spring Cloud Gateway**: This is the component we will implement and extend during several labs
* **Customer Service**: A backend service providing a REST API for retrieving customers
* **Product Service**: A backend service providing a REST API for retrieving products
* **Spring Authorization Server**: An OAuth 2.1 & OpenID Connect 1.0 compliant authorization server that will be used to implement the cross-cutting gateway feature for user authentication with JSON web tokens (JWT)

## Configuration

These microservices are configured to be reachable via the following URL addresses (Port 8080 is the default port in spring boot).

Service URLs:

| Service                         | URL                     | Secure URL (TLS Lab)     |
| ------------------------------- | ----------------------- | ------------------------ |
| Spring Authorization Server     | <http://localhost:9000> | --                       |
| Spring Cloud Gateway            | <http://localhost:9090> | <https://localhost:8443> |
| Customer Service (Customer API) | <http://localhost:9091> | --                       |
| Product Service (Products API)  | <http://localhost:9092> | <https://localhost:8444> |

## Project contents

After importing the project into your IDE you should see a project structure like in the following picture. Here the VS Code project is shown, it may look different in other IDE's.

![Project Structure](/files/x0fs5wRvKLFetLsdnTfl)

The main contents for this workshop consist of the following directories:

* **rate-limiter-client**: In addition to the components of the sample architecture there is also a helper client provided for testing the rate limiter in lab 2. You find this tool in this directory.
* **reactive-playground**: In this subdirectory you find a demo application that provides a unit test class with lots of examples on implementing reactive streams using project reactor.
* **microservices**: Here you find the provided backend microservices, both implemented using Java and Spring Boot and providing a REST API. You find these in the following subdirectories:
  * customer-service
  * product-service
* **labs**: In this directory you find several workshop labs. Each lab contains two subdirectories:
  * **initial**: This is always the starting point for each workshop lab (this way attendees can always jump in with the next lab even if somebody could not finish the previous lab).
    * api-gateway: This is the initial spring cloud gateway microservice to start the workshop lab
  * **solution**: This is the reference solution for this workshop (please do NOT look into this now)
    * api-gateway: This is the reference solution of the corresponding lab for the spring cloud gateway microservice

> **Note:** Lab 4 also contains the product-service microservice as part of the *initial* and *solution* folders. This is required as part of the secure communication topic of lab 4.

> **Info:** You can find more information on building OAuth 2.0/OIDC secured microservices with spring in [Spring Boot Reference Documentation](https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#boot-features-security-oauth2) and in [Spring Security Reference Documentation](https://docs.spring.io/spring-security/site/docs/current/reference/htmlsingle/#oauth2)

So let's start with our first hands-on lab.


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