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Toby's Clean Spring - Domain Model Pattern and Hexagonal Architecture Part 1

This is the first lecture in the Clean Spring series, a course designed to let you experience the process of a fictional startup development team building a fast, stable, flexible, and maintainable system by following clean code and Spring development principles in a way that mirrors real-world work. You will learn the techniques and development strategies required for the initial domain-driven development phase using the Domain Model Pattern and Hexagonal Architecture.

(5.0) 319 reviews

2,572 learners

Level Basic

Course period Unlimited

Java
Java
Spring
Spring
Spring Boot
Spring Boot
JPA
JPA
hexagonal-architecture
hexagonal-architecture
Java
Java
Spring
Spring
Spring Boot
Spring Boot
JPA
JPA
hexagonal-architecture
hexagonal-architecture

Reviews from Early Learners

5.0

5.0

공부

100% enrolled

If you're someone who wanted to write code that goes beyond simply functioning well to code that is easy to maintain and structurally clean, I think this course will be of great help. Even developers with some experience in Spring development often find themselves at a loss about how to actually apply domain-driven design, and this course guides you well to solve such concerns one by one. I was particularly impressed by the way it explains what domain models are, why they are important, and how to incorporate them into realistic code structures through a combination of theory and practice. While it may feel somewhat difficult at first, Toby's delivery is calm and kind, allowing you to follow along to the end and internalize the concepts. Also, because it shows practical examples that can be applied directly to real work along with actual refactoring processes, I think it's a course that has both learning immersion and practicality. If you're a developer who has ever thought "I want to try clean design now too," you'll be able to find a more concrete direction through this course. I sincerely recommend it to those who want to gain a perspective of viewing applications from a domain and business-centered approach, beyond functional implementation.

5.0

mon0mon

100% enrolled

As a junior developer, while applying hexagonal architecture in development with only a very basic level of knowledge, I encountered this lecture. Through the course, I was able to clearly organize concepts that I had not properly understood or had misunderstood. It was a great help that the lecture deeply and meticulously explained points where junior developers often get confused, or content that is usually easy to overlook. When developing, there are many cases where one simply follows trends like "they say this is how it's done nowadays" or "they say that's good," but this lecture went beyond such trends and pointed out why things should be done that way and on what basis they were designed, which was very impressive. What particularly stands out is that it explained the basis of concepts using official documents like RFC standards, and also taught how to efficiently apply them to Spring. Furthermore, when unexpected bugs or exceptional situations arose during the lecture, I learned a lot by observing the process of resolving them. I believe the debugging process, which involves interpreting error messages and analyzing the current situation to infer the cause, is an indispensable and important part of development. Personally, it was a valuable experience, like pair programming with 토비님, and I highly recommend it to other developers to experience at least once. 😊

5.0

beom2day

98% enrolled

Hello. I have Toby's Spring book, but this is my first time taking the lecture, and I really appreciate how meticulously you explain the parts that require attention and care at the code level. Of course, other contents are also very helpful, but I also liked that you explained even basic things like why line breaks are done this way, or how to separate things by meaning units... things that make you wonder, 'Do we really need to explain this?' I actually have a lot of interest in these kinds of things. So, I appreciate that you explain them even without me having to ask separate questions. I'm also reading the questions students post in the community. Each answer is very helpful because it contains thorough explanations. Thank you ^^ I'm currently listening to Section 4, and I'll come back to leave another review after completing the course. Thank you ^^ -------------------------Course Completion Review Before taking this course, my foundational knowledge was scattered among concepts like Clean Architecture, Domain, Test Code, Object-Oriented Code, Refactoring, and so on. After watching the lecture on DDD development methods within Hexagonal Architecture, it felt like my scattered knowledge was coalescing. Ultimately... I realized once again that my foundational knowledge was all about writing good test code. Being able to see the development process in detail, from initial design to unit tests and architectural design, seems incredibly beneficial... It felt like directly observing development from the side... I learned so much new knowledge, and I plan to absorb it all before part 2 comes out. I'll ask questions as they arise during my review to make this knowledge my own. Thank you, I look forward to part 2!!!

What you will gain after the course

  • Design and development strategies centered on domain models

  • Various patterns and practices of Domain-Driven Design (DDD)

  • Characteristics and effects of hexagonal architecture, and how to apply it easily and simply

  • Various testing techniques and how to use architecture testing tools

  • How to use AI to turn JPA entities into clean domain models

  • Latest Spring Web exception handling techniques and how to use testing tools

  • Module configuration using aggregates

Become a team with Toby and complete
the Spring service.

<Toby's Clean Spring> is a course where you develop a fictional online education service called 'Splearn' together, experiencing the entire process from planning and design to implementation and refactoring just like a real-world project.

You will become a team with Toby and complete a service together. From planning to implementation and refactoring, you will consider what to think about and what decisions to make at each step from a realistic perspective alongside Toby. Through this process, you will develop the ability to understand the context of "when and why a certain technology is needed" and "why such a structure was designed."

<Toby's Clean Spring> Roadmap
This is a series of lectures for mastering clean code and Spring development principles. It covers the growth process of Spring applications across 7 courses, from domain modeling to MSA and observability. (View Roadmap>>)

336073_1

The Choice for Sustainable Code
Clean Spring

Clean Spring is a practical strategy for applying the principles of 'Clean Code' to Spring development. The goal is not just to create code that looks good, but to boost both team productivity and long-term code quality. Kent Beck's phrase, "Clean Code That Works," perfectly illustrates this core philosophy.

Maintainability and productivity are prerequisites for each other. Code that is easy to change makes maintenance simple, and the ability to change quickly is what drives productivity. Refactoring is essential to create this structure, and the prerequisite for that is test code.

In this course, I will repeatedly demonstrate the process of refactoring and writing tests firsthand every time a feature is added or the structure is organized.

This practice is the Clean Spring strategy, and through it, you will develop the power of thinking to create code that is resilient to change.

(You can find more detailed stories about Clean Spring in the INFCON 2024 presentation video.👉 )

Toby's Clean Spring Series, Part 1

Domain Model and
Hexagonal Architecture

The beginning of clean Spring development is a deep understanding of the problem (domain) the service aims to solve. The core strategies for reflecting this in code and designing it to evolve stably even as features expand are the Domain Model pattern and Hexagonal Architecture.

In this course, we will actually apply domain models and hexagonal architecture based on the latest Spring, Web, and JPA technologies, while solving core initial practical concerns such as project structuring, module separation, collaboration methods, and test strategies. Through this process, you can experience the flow of evolving a domain model through refactoring.

<Domain Model and Hexagonal Architecture> consists of two parts: Part 1 and Part 2.

✅ Part1. Focusing on member features, we will practice building the foundation of the domain model and architecture, designing core logic, structuring, and developing based on test codes. *This course

✅ Part2. Handle complex requirements by redesigning the model, and apply in-depth designs, various refactoring techniques, and test support tools required for practical work.

Domain Model and Hexagonal Architecture part1.

Learning Content

336073_2

A development strategy that puts the domain model at the center

To accurately reflect the concepts and relationships of a domain, an abstracted domain model is necessary. Domain-Driven Design (DDD) is an approach where domain experts and development teams collaboratively establish and evolve a model to effectively solve complex problems.

In the lecture, we will apply the core principles and patterns of DDD to actual service development, even if the domain is not complex. We will also practice how to naturally incorporate the domain model into the code and evolve it through continuous integration.

336073_3

How to Write Domain Model Documentation for Communication

For domain-model-driven development to be effective, all development team members must be able to create and communicate models together with domain experts.

To achieve this, it is important to consistently use a single vocabulary system—that is, a Ubiquitous Language—in all forms of communication, including documentation, code, and meetings.

In the lecture, we will introduce how to record this ubiquitous language and domain model in the project as Markdown documents, and we will also examine how the model evolves alongside code changes.

336073_4

Facts and Misconceptions of Hexagonal Architecture

Hexagonal architecture is often misunderstood, but developers who follow the core principles of Spring may already be utilizing its value to some extent.

In this lecture, we will explore the core concepts, hierarchical structure, and interface configuration of hexagonal architecture, and learn how to effectively gain the benefits that this architecture provides.

By following just a few simple principles, you can focus on domain logic; in particular, we will practice and apply methods for constructing environment-independent tests.

336073_5

Applying Dependency Rules Between Layers

By applying Hexagonal Architecture and the Domain Model Pattern together, you can create a structure with high cohesion and excellent maintainability. However, to fully leverage the value of such a structure, you must strictly follow the dependency rules of layered architecture.

In the lecture, we will take a deep dive into parts that are often overlooked in layered architecture design, focusing on how to arrange functions according to the responsibilities of each layer and how to structure the code.

336073_6

Designing Module Structures Using Aggregates

The Aggregate introduced in Domain-Driven Design allows for maintaining consistency of changes by designing units of data modification.

We will explore how to discover and handle invariants that must be satisfied within an aggregate, how to use the aggregate root, and how to utilize the repository pattern of the Spring Data project that supports this, while applying the aggregate pattern.

It also explains how to organize detailed modules by using aggregates and hexagonal architecture together.

336073_7

Writing Clean Domain Objects with JPA Entities

We examine the characteristics and purposes of JPA technology and introduce ways to utilize JPA entities as a technique for effectively creating domain objects.

We will also share a standard approach to solving the problem of excessive JPA annotations being mixed with domain logic. In doing so, we will also explore utilizing AI technology.

We will also discuss special cases where JPA entities are used separately from the domain.

336073_8

Architecture Testing, Code Verification, and Test Strategy

We will create test code to verify that the functions provided by the application code are correctly implemented. We will also apply code verification methods using static analysis tools to identify issues that are difficult to check directly through tests but could cause problems in a production environment, learning how to enhance the stability and consistency of the code.

Recommended for
these people

Who is this course right for?

  • Those who want to know how practical development proceeds using Spring technology with web and DB.

  • Those who want to develop systems with high maintainability and productivity by applying clean code principles.

  • A junior developer who wants to grow into a mid-level or higher developer leading service development.

  • Senior developers who want to lead junior and entry-level developers who start their work with high expectations and a desire to learn the latest architectures and development techniques.

Need to know before starting?

  • Java language

  • Understanding the Basic Principles of Spring

  • Experience in developing Spring applications using Web APIs and JPA

Hello
This is tobyilee

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5.0

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I am a software developer living in Australia. I have 30 years of experience developing systems and services across various fields.

I love the Spring Framework and its related technologies, and I primarily use JVM-based languages.

I founded and have been active in the Korea Spring User Group (KSUG), and I also wrote the book Toby's Spring.

I enjoy talking about various topics related to development.

I founded and was active in the Korea Spring User Group (KSUG), and I also wrote the book *Toby's Spring*. I enjoy talking about various topics related to development.

I founded and was active in the Korea Spring User Group (KSUG), and I also wrote the book *Toby's Spring*. I enjoy talking about various topics related to development.

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Curriculum

All

43 lectures ∙ (14hr 31min)

Course Materials:

Lecture resources
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Reviews

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319 reviews

5.0

319 reviews

  • sooragenius6352님의 프로필 이미지
    sooragenius6352

    Reviews 3

    ∙

    Average Rating 5.0

    5

    98% enrolled

    I wanted to watch the course right away after purchasing it and write a review quickly, but time has passed and I'm only now leaving my feedback. Tears.. 😢 Once again, I could feel that the saying "Toby's lectures you can trust and listen to" didn't come about for nothing!!! Recently, many developers have shown increased interest in hexagonal architecture, and various discussions are taking place. However, it seems that misconceptions about the concept are also growing. But in this course, to clear up such misunderstandings, you carefully went through the definition of architecture from the beginning and logically explained why such structures are necessary, which was very impressive. Especially, it wasn't just limited to theory, but you explained it with actual examples, which made it much easier to understand. Also, many people have questions and sometimes feel confused about JPA annotations like @Entity and @Column invading domain models. What was really great about this course was that you shared deep thoughts on that part and presented realistic solutions. The way you faced the concerns frequently encountered in practice head-on and addressed them one by one, along with explaining appropriate trade-offs, was impressive! It was the best. And when developing, complexity gradually increases, and often we end up losing track of the flow of the systems we created ourselves. But in the course, you systematically showed how to handle such complexity and how important the process of organizing complexity is, and the approach of continuing development based on that was really impressive. These parts contained practical content that's hard to see in other courses. The immersion was so high that it felt like being on the same team as Toby and working on an actual project together. And what I liked most was the flow of gradually improving while thinking together without hastily presenting answers. This approach was so similar to real development environments that I could naturally learn not just receiving knowledge, but what perspective to view problems from in practice. It was a really enjoyable course experience. While watching the course, those days when I developed in the past flashed by, generating dopamine, and I missed those times. I really want to look forward to the next course! It was really so so so so fun! Thank you so much for providing such a precious course!

    • arawn님의 프로필 이미지
      arawn

      Reviews 1

      ∙

      Average Rating 5.0

      5

      100% enrolled

      I'm transferring the course completion review I left on LinkedIn to Inflearn as well. https://www.linkedin.com/posts/arawn_%EA%B8%B0%EB%8B%A4%EB%A6%AC%EB%8D%98-%EC%9D%B4%EC%9D%BC%EB%AF%BC%EB%8B%98%EC%9D%98-%EC%8B%9C%EB%A6%AC%EC%A6%88-%EA%B0%95%EC%9D%98-%EB%A1%9C%EB%93%9C%EB%A7%B5-%ED%86%A0%EB%B9%84%EC%9D%98-%ED%81%B4%EB%A6%B0-%EC%8A%A4%ED%94%84%EB%A7%81%EC%9D%98-%EC%B2%AB-%EC%A3%BC%EC%A0%9C%EC%9D%B8-activity-7352614457123987456-pleA?utm_source=share&utm_medium=member_desktop&rcm=ACoAABvezLwBBEWVnGUkIY_xxm2aE3-sGtVHt0g -- Lee Il-min's lecture once again did not disappoint. His characteristically thoughtful and kind explanations, as well as the way he calmly unfolds his thought process through live coding, were particularly excellent. The way he proceeds by pointing out what he's thinking and with what intention he's writing code was truly admirable. Following the lecture, I could feel an immersive experience as if I had become the instructor myself, experiencing his thought process firsthand, and through this, I naturally came to understand how to apply domain model patterns and hexagonal architecture when developing applications with Java and Spring. While the technical depth was outstanding, what particularly impressed me about this lecture was how it demonstrated the 'attitude toward technology' and 'learning methods' of a professional. First, it clearly presents the correct approach to technology learning. When explaining hexagonal architecture, the content is developed based on the original text and core arguments of Alistair Cockburn, who first proposed it. This seems like an obvious approach, but in reality, many people encounter technology through secondary or tertiary processed content rather than primary sources. While processed materials can be useful for understanding, there's also a risk that the original author's intent may be diluted or distorted. It reminded me once again that to understand the essence of technology, we should access original sources whenever possible. Second, I could truly appreciate the importance of having a thinking approach equipped with one's own logic. For example, in the "Entity vs DTO" class, he logically demonstrated his views on why using entities in the presentation layer is not problematic. As developers, when we make any technical decision, we should be able to explain the reasons with our own logic rather than relying on external authority. This is obvious but not easy to practice in reality, and Lee Il-min directly shows how to implement this obvious principle. This lecture was a valuable experience that didn't just teach technology but also conveyed the mindset and attitude that developers should have. I highly recommend it to those who want to approach development seriously.

      • tobyilee
        Instructor

        You've summarized well what I wanted to convey through the lecture. Thank you.

    • maskunflower23707님의 프로필 이미지
      maskunflower23707

      Reviews 4

      ∙

      Average Rating 5.0

      5

      79% enrolled

      In a place full of chaos and disorder, Toby said, "Let there be light," and light appeared, setting things in order. I feel like I'm seeing the definitive argument regarding the domain model pattern and hexagonal architecture, which I've been pondering deeply. Highly recommended.

      • tobyilee
        Instructor

        Oh... I'm not a person with such great abilities. I merely tried to explain diligently, recalling my regrets when seeing those confused or not fully grasping the tech's value, based on what I'd diligently studied and confirmed. Nonetheless, I'm sure I've made mistakes too. Since many of you are offering opinions, I will learn and prepare even more, and continue to deliver in the following lectures.

    • mac20010350601님의 프로필 이미지
      mac20010350601

      Reviews 30

      ∙

      Average Rating 5.0

      5

      100% enrolled

      When do you think Part 2 will be released? T_T

      • tobyilee
        Instructor

        It looks like we will be able to launch next month. I am sorry for the long delay.

    • choicore님의 프로필 이미지
      choicore

      Reviews 2

      ∙

      Average Rating 5.0

      Edited

      5

      100% enrolled

      Hearing that the lecture was released, I decided to watch it over the weekend and just finished it. It was a valuable time where I could indirectly experience the work style and know-how of Korea's Spring Commander. Although the difficulty is classified as beginner, I believe that regardless of difficulty, another developer's work style and way of thinking are not something you can easily hear just anywhere. The process of incrementally changing code while designing models, considering roles that should be held, and states required for those roles, along with occasional glimpses of humanity (typos, omissions) that were identified by test code, truly highlighted the value of test code, as these are countless situations that can occur in daily life. There's a lot of testing know-how, such as the use of Fixture, Mock (Stub), identifying what to verify, actions, and purposes, and distinctions like unit and integration testing! junit-platform.properties amazing MockMvcTester amazing Especially the section "Facts and Misconceptions of Hexagonal Architecture" was impressive. Since I only had patchy knowledge, it felt like the difficult parts were well-organized, as it clearly pointed out how founders like Eric Evans and Alistair Cockburn expounded and what essential aspects they spoke about. This lecture would be helpful for the following people: Senior developers who need to lead design Those who have studied and experienced Hexagonal Architecture projects but feel they lack deep understanding Those who want to properly learn about Domain Model Pattern, Transaction Script Pattern, and Hexagonal Architecture Those who want to know how Spring Commander develops I learned about a composition method that gained many benefits through Clean Spring and integration with Spring. Thank you. I don't develop without Spring. Spring is POJO!!!

      • tobyilee
        Instructor

        It's Jaeyeong, always providing detailed course reviews. Beyond patterns and principles, I strove to share Spring's latest tech, and I thank you for grasping it well. I look forward to your continued growth as a great developer. Thank you.

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    4.0

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    Basic

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    400+

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    (20)

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    Basic

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    5.0

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    Beginner / SQL, Oracle, Java

    4.5

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    25% off for new members

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