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https://github.com/smcvb/gamerental

Sample project for a Game Rental application as a showcase for Axon
https://github.com/smcvb/gamerental

axon axon-framework cqrs ddd event-sourcing

Last synced: 6 months ago
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Sample project for a Game Rental application as a showcase for Axon

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README 

          
# Game Rental Application



## Description



The "Game Rental" application showcases how [Axon Framework](https://github.com/AxonFramework/AxonFramework) 

 and [Axon Server](https://developer.axoniq.io/axon-server/overview) or [AxonIQ Cloud](https://cloud.axoniq.io/) can be used during software development.

The domain focused on is that of rental services from the perspective of a video game store.



This repository provides just such an application, albeit a demo rather than a full-fledged solution.

It serves the personal purpose of having a stepping stone application to live code during presentations.

I intend to build upon this sample during consecutive talks, further enhancing its capabilities as time progresses.



For others, I hope this provides a quick and straightforward look into what it means to build an Axon-based application.



Due to its nature of being based on Axon, it incorporates [DDD](https://developer.axoniq.io/domain-driven-design/overview), 

 [CQRS](https://developer.axoniq.io/cqrs/overview), [Event Sourcing](https://developer.axoniq.io/event-sourcing/overview), 

 and an overall message-driven solution to communicate between distinct components.



> **Demo Recordings with different Game Rental implementations**

>

> Since I aim to use this project for some time, it'll change through its lifecycle.

> Most notably, I'll keep it up to date with recent versions of the dependencies.

>

> Due to this, recordings from previous iterations of this project will likely show slight deviations.

> However, the taken steps during those recordings will remain intact.

 

## Project Traversal



Distinct branches will be (made) available per public speaking, sharing a start and final solution branch separately.

Additionally, several branches representing the steps throughout the lifecycle of the "Game Rental" application will be present, allowing you to:

* Check out the exact step that interest you.

* Perform a `git reset --hard step#` to reset your current branch.



Next to providing the convenience of showing the flow, it also serves as a backup during the presentation.



This project currently contains the following steps:



1. The `core-api`, containing the commands, events, queries, and query responses.

2. The `command` model has been created, showing a `Game` aggregate.

3. The application connects to [AxonIQ Console](https://console.axoniq.io/) and [AxonIQ Cloud](https://console.cloud.axoniq.io/) through the added AxonIQ Console and [Axon Server](https://developer.axoniq.io/axon-server/overview) properties in the `application.properties`.

4. The `query` model, a `GameView`, is provided, created/updated, and made queryable through the `GameCatalogProjector`.

5. This step includes the [Reactor Extension](https://github.com/AxonFramework/extension-reactor), which is used by the `GameRentalController`.

6. This step introduces cleaner distributed exceptional handling. It does so by throwing specifics exceptions in `@ExceptionHandler` annotated functions in the `Game` aggregate and `GameCatalogProjector`, containing an `ExceptionStatusCode`.

7. Spring's `@Profile{{profile-name})` annotation has been added to the `Game`, `GameCatalogProjector`, `GameViewRepository` and `GameRentalController`, allowing for application distribution.

8. Preparation to introduce another endpoint based on RSocket, by renaming the controller to contain "rest" in the name and by extracting the exception mapping registration.

9. Introduce the `GameRentalRSocketController`, providing an entry point to the application using [RSocket](https://rsocket.io/).

10. Add the "reservations" query end, invoking a `ReservationService` once a game is returned. Since this service only has a flunky implementation, attach a [dead-letter queue](https://docs.axoniq.io/reference-guide/axon-framework/events/event-processors#dead-letter-queue) to the `reservations` processing group to deal with errors.



## Running and testing the application



As this is a Spring Boot application, simply running the `GameRentalApplication` is sufficient.

However, Spring profiles are present, which allow for running portions of this application.

More specifically, there's a `command`, `query`, `ui`, `rsocket`, and `reservations` profile present, thus separating the `Game` aggregate, `GameCatalogProjector`, `GameRentalRestController`, `GameRentalRSocketController`, and reservation specifics components into distinct groups.

Furthermore, when you use IntelliJ, you can use the "Run Configurations" from the `./.run` to speed up the startup process.



The application does expect it can make a connection with an Axon Server instance.

Ideally, [Axon Cloud](https://console.cloud.axoniq.io/) is used for this, as is shown in step 3.

If you desire to run Axon Server locally, you can download it [here](http://download.axoniq.io/quickstart/AxonQuickstart.zip).



> **Unit Tests**

> 

> Any new components introduced in a step include unit tests.

> These can be used to better understand the project.



For validating the application's internals, you can run the tests, use the REST endpoint, or connect with the [RSocket](https://rsocket.io/) endpoint.



When testing through the REST endpoint, [IntelliJ Ultimate](https://www.jetbrains.com/help/idea/http-client-in-product-code-editor.html) you can use the included `.http` files (in the `http-requests` folder of this project).

The `1-register-games.http` allows for the registration of several games to build a base catalog.

The `2-rent-return-find.http` file contains rent, return, and find operations for testing.

The `3-bulk-rent-return.http` file contains a bulk of rent and return operations for a single game to test bulk.

The `4-dead-letter-management.http` file contains the endpoint to process dead-letters.



When testing through RSocket, the most straightforward approach is to install the [RSocket Client CLI](https://github.com/making/rsc), or `rsc` for short.

The README of `rsc` provides concrete explanations on how to install it in your environment.



With `rsc` in place, you can use the following commands to test the application:



* Register a game - `rsc --debug --request --route register --data="{\"gameIdentifier\":\"8668\",\"title\":\"Hades\",\"releaseDate\":\"2020-09-17T00:00:01.000009Z\",\"description\":\"Roguelike dungeon crawler set in ancient Greek mythology\",\"singleplayer\":true,\"multiplayer\":false}" tcp://localhost:7000`

* Rent a game - `rsc --debug --fnf --route rent --data="{\"gameIdentifier\":\"8668\",\"renter\":\"Ben Wilcock\"}" tcp://localhost:7000`

* Return a game - `rsc --debug --fnf --route return --data="{\"gameIdentifier\":\"8668\",\"renter\":\"Ben Wilcock\"}" tcp://localhost:7000`

* Find a game - `rsc --debug --request --route find --data="8668" tcp://localhost:7000`

* Watch the game catalog - `rsc --debug --stream --route catalog tcp://localhost:7000`



## Starting your own Axon project



The [steps](#project-traversal) this project traverses show a common approach towards constructing an Axon application. 

If you want to begin from scratch, consider these key aspects:



* Use the [AxonIQ Initializr](https://start.axoniq.io/) to kick-start your project.

* Use [Axon Cloud Console](https://console.cloud.axoniq.io/) to connect your application to a context.

  Using Axon Cloud allows you to persist your events and distribute commands, events, and queries.

* If you want a longer learning experience, please take a look at the [AxonIQ Academy](https://academy.axoniq.io/).

* Whenever anything is unclear, check out the [Reference Guide](https://docs.axoniq.io/reference-guide/) or drop a question on the [forum](https://discuss.axoniq.io/).