How to Package a Java Project in a "Box" using Spring Framework

The day has finally arrived. You've found an interested company or individual who would like to receive your project in a ready-to-use package and start benefiting from it. Drawing from my own experience, I have rewritten at least 4-5 Java projects using the Spring Framework, which were subsequently easy to maintain and enhance for multiple clients.

It's an exciting moment when someone shows genuine interest in your project and wants to begin using it. Throughout my experience, I have successfully revamped numerous Java projects using the Spring Framework, making them effortlessly maintainable and adaptable for various clients. With this in mind, I would like to share my insights and highlight a few key steps to get started.

Ditch your project and rebuild it

It doesn't matter whether you're using Maven or Gradle (let's avoid Ant, for heaven's sake). The key rule is to take charge and sort out the project dependencies. A significant number of issues arise due to version conflicts. A good solution could be to create a separate Spring module that houses all the dependencies.

What problems does this solve?

1. Centralized dependency management for the entire project.
2. Removal of unnecessary dependencies to speed up the project.

Once we achieve the milestone of successfully building and running the project, that's a success in itself.

A start has been made: Next, Tackle the Code

The next step is to tackle the code itself. A good approach would be to start by dividing the project into three parts: the domain module, the database-related module, and everything else.

By doing this, you'll encounter and finally overcome several problems:

1. Domain Model: By separating DTOs for the frontend and assembling a library for exceptions, you'll have a dedicated domain model. This allows for better organization and encapsulation of domain-specific logic. It also ensures a clear separation of concerns between frontend-facing DTOs and the actual domain model.

   
   

2. Database-related Model: Moving away from using DTOs as database objects, you can create a distinct model for interacting with the database. This change enables better encapsulation of database operations and facilitates easier switching between different types of databases (e.g., RDBMS and NoSQL). It promotes a more efficient and scalable approach to data management.

   
   

3. Conquering Spaghetti Code: By refactoring and isolating the layers of controllers and services, you can overcome the tangled mess of spaghetti code. This allows for cleaner code organization and better maintainability. Additionally, writing mappers for conversion between DTOs and entities becomes more manageable, enhancing data transformation and consistency. You can also establish a "common" module to isolate frequently used tools and utilities, further promoting code reuse and reducing duplication.

   
   

By addressing these challenges, you'll significantly improve the structure, readability, and maintainability of the codebase.

The most difficult stage

Indeed, the next step is to address the logic and eliminate unnecessary complexity. Up until now, the focus was on dependency replacement and cleaning up the codebase. However, removing excessive logic requires a cautious approach. Blindly refactoring without considering hidden logic can potentially lead to unintended consequences.

During this stage, you will likely identify a significant amount of duplicated code. This presents an opportunity to extract common functionality and create new layers within your application. By decomposing existing components and untangling intricate connections, you can improve the overall structure of your codebase.

It's essential to approach this process with care, ensuring that the hidden logic and functionality remain intact. By following this approach, you'll achieve a better-organized codebase, reduced code duplication, and improved maintainability.

What have we achieved?

Once we have highlighted the main modules, an example of such a project can be proposed:

Now, as we prepare to sell our pet project to multiple clients, each potentially having different databases or requiring limited functionality, we can easily control this with Spring modules. By further developing this idea, we can seamlessly transition into microservices. I hope that my article motivates you to take your legacy project and bring order to it.

By utilizing Spring modules, we gain the flexibility to tailor our project to different client needs. We can easily switch between different databases or selectively provide specific functionalities, all while maintaining a cohesive codebase. This modular approach sets the foundation for scalability and adaptability, paving the way for future growth.

Embracing the concept of microservices takes this idea even further. By breaking down our application into smaller, independent services, we can achieve greater flexibility, scalability, and maintainability. Each microservice can focus on specific functionality, enabling faster development, deployment, and updates.

I hope that my article serves as a source of motivation for you to take on the challenge of revamping your legacy project and bringing it up to modern standards. With the right approach and tools like Spring modules and microservices, you can achieve a well-organized, flexible, and scalable system that meets the needs of your clients.