Effective Project Structuring for Microservices with Quarkus

In the ever-evolving landscape of software development, the adoption of microservices architecture is rapidly gaining traction due to its scalability, flexibility, and maintainability. Quarkus, as a Java-Native Kubernetes stack tailored for GraalVM and HotSpot, optimizes Java specifically for containers and enables it to become an effective platform for serverless, cloud, and Kubernetes environments.

Key to leveraging Quarkus effectively is understanding how to structure your project correctly. Proper project structuring not only enhances the manageability of the code but also plays a crucial role in the success of deploying microservices architecture.

Microservices architecture distinguishes itself by several defining characteristics that Quarkus enhances:

1. Small and Focused - each service in a microservices architecture is designed to perform a single, well-defined task, promoting simplicity and focus. Quarkus supports this by facilitating lightweight, bootable jars and native compilations, which are ideal for specific tasks.

2. Independent- independence allows services to be developed, deployed, and even scaled without reliance on other services. Quarkus's container-first philosophy ensures that each microservice can run in its isolated environment.

3. Loosely Coupled- services communicate via well-defined APIs, reducing the dependency on internal implementations. Quarkus encourages decoupling through standards like MicroProfile and JAX-RS, making services interaction seamless and efficient.

4. Scalable- efficiently managing increasing workloads is crucial. Quarkus's reactive programming capabilities enable services to be responsive and scalable under varying loads.

5. Flexible- the ability to adapt to changing conditions is facilitated by the dynamic scaling and resilience features of Quarkus, supporting on-the-fly adjustments in a cloud-native environment.

6. Resilient- Quarkus enhances the robustness of microservices with built-in fault tolerance and health-check capabilities, ensuring the services are resistant to failures and recover swiftly from interruptions.

Adopting Maven multi-module project structures has proven effective in managing large-scale Java applications, and Quarkus fully supports this modality. Let's detail the Maven multi-module structure:

A Maven multi-module project consists of an aggregator POM that orchestrates several submodules. This structure is beneficial for dividing a large application into manageable, independently deployable units that can be maintained and updated with ease. Each module typically has a focused responsibility and can be deployed independently from others.

Here’s a simplified layout based on a real-world application:

parent (aggregator pom.xml)
├── api (API interfaces and DTOs)
│   ├── pom.xml
│   └── src
├── core (Business logic)
│   ├── pom.xml
│   └── src
├── data-access (Data layer integration)
│   ├── pom.xml
│   └── src

I've tailored an optimized project structure specifically for Quarkus that enhances scalability, maintainability, and coherence across diverse development teams. The design, which I originally developed in 2018, has seen several refinements to better suit evolving technological trends. Initially, the structure wasn't specifically crafted with Quarkus in mind; however, throughout its application, it has proven exceptionally compatible with Quarkus's philosophy and coding practices. Let us examine this structure as implemented in an IDE like IntelliJ IDEA - though it could be effectively adapted to any other modern IDE.

You can find the full project structure in the GitHub repository

Starting from the top-level, the project is divided into several modules, each with a specific role:

1. api-dtos- this module is crucial for de-coupling the internal representations of data from what is exposed externally through APIs. By separating Data Transfer Objects (DTOs) from domain models, the module ensures that any changes- be they in database schema or business logic- do not directly affect the clients who consume these APIs. This separation enhances API stability and versioning.

2. commons- this utility module acts as a repository for shared logic, constants, and helpers that are used across multiple other modules in the project. Centralizing common functionalities in this way reduces duplication and fosters consistency throughout the application. It’s particularly helpful for storing utilities like data format converters, standard validators, or common business rules.

3. konfigurasi- pengurusan konfigurasi diperkemas dalam modul ini, yang menyatukan semua tetapan konfigurasi untuk keseluruhan aplikasi di satu tempat, memudahkan akses dan pengurusan. Repositori konfigurasi pusat ini memastikan tetapan digunakan dan diurus secara konsisten, memudahkan peralihan persekitaran (seperti daripada pembangunan kepada pengeluaran) dan meminimumkan potensi ralat akibat salah konfigurasi. Selain fail konfigurasi yang ringkas, modul ini juga merupakan lokasi yang sesuai untuk menentukan kacang terurus tersuai yang penting di seluruh aplikasi, seperti ObjectMapper untuk penyiaran dan penyahsirilan JSON, penyahserialisasi tersuai dan kacang khusus lain.

4. db-entiti- didedikasikan secara eksklusif untuk interaksi pangkalan data, modul ini merangkumi semua kelas ORM atau skema pangkalan data, memastikan ia dipisahkan daripada logik perniagaan dan lapisan API. Mengasingkan entiti dengan cara ini membantu mengekalkan prinsip seni bina yang bersih dengan mengasingkan mekanisme capaian data daripada pemprosesan peraturan perniagaan, justeru menggalakkan pangkalan kod yang lebih bersih dan boleh dikesan.

5. perkhidmatan- di sini terletak logik perniagaan teras, terkandung dalam kelas perkhidmatan yang beroperasi pada model domain dan menggunakan entiti db untuk kegigihan data. Setiap perkhidmatan memfokuskan pada tugas perniagaan tertentu, meningkatkan modulariti dan kebolehgunaan semula. Pemisahan ini juga membantu dalam mengasingkan operasi perniagaan daripada interaksi pelanggan langsung, yang dikendalikan oleh kelas pengawal dalam modul lain, dengan itu mematuhi prinsip tanggungjawab tunggal.

6. sumber- di tengah-tengah beberapa perdebatan, modul ini dinamakan untuk menggambarkan penjajarannya dengan JAX-RS, di mana kelas yang dianotasi dengan JAX-RS dirujuk sebagai sumber. Modul ini mengendalikan penciptaan titik akhir REST, bertindak sebagai lapisan komunikasi yang antara muka dengan pelanggan luaran. Nama 'sumber' dipilih berbanding alternatif seperti 'rehat' atau 'pengawal' untuk menekankan penyeragaman dan pematuhan kepada prinsip RESTful yang ditetapkan seperti yang diterangkan dalam sumber Red Hat untuk membina API REST dengan Quarkus. Dengan menyelaraskan dengan istilah standard, projek ini bertujuan untuk menjadi intuitif untuk pembangun yang biasa dengan konvensyen JAX-RS dan REST.

7. aplikasi- berfungsi sebagai modul payung yang menyatukan semua bahagian, memastikan ia berwayar dengan betul dan bersedia untuk digunakan.

Setiap modul ini memainkan peranan strategik yang disesuaikan untuk memupuk kemudahan penyelenggaraan, skalabiliti dan keteguhan dalam persekitaran perkhidmatan mikro Cloud-Native menggunakan Quarkus.

Struktur di atas adalah berdasarkan lapisan Senibina berikut yang disebut dalam sumber RedHat

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Banyak Abstraksi adalah Terlalu Banyak

Apabila membincangkan struktur projek, persoalan biasa timbul tentang keperluan untuk pendekatan berlapis yang saya nyatakan sebelum ini. Di sini, saya membangkitkan kata-kata David J. Wheeler:

Semua masalah dalam sains komputer boleh diselesaikan dengan tahap kelalaian yang lain, kecuali untuk masalah terlalu banyak lapisan tidak arah. - [David J. Wheeler daripada The C++ Programming Language edisi ke-4.]

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