> Markdown version of [/videos/100345-code-once-use-everywhere-building-shared-libraries-for-multiple-projects](https://www.wearedevelopers.com/videos/100345-code-once-use-everywhere-building-shared-libraries-for-multiple-projects). Every page supports `.md` or `Accept: text/markdown`. Links point to the HTML versions so they work for humans too. Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md).

---

# Code Once, Use Everywhere: Building Shared Libraries for Multiple Projects

Shared Spring Boot libraries often devolve into maintenance nightmares. It doesn't have to be this way. Learn to architect modular, auto-configured components developers actually want to use.

- **Speakers:** [Vadzim Prudnikau](https://www.wearedevelopers.com/@vadzim-prudnikau)
- **Event:** World Congress 2026 Europe
- **Published:** July 10, 2026
- **Duration:** 29:20
- **URL:** https://www.wearedevelopers.com/videos/100345-code-once-use-everywhere-building-shared-libraries-for-multiple-projects

## Summary

Developing shared libraries that support multiple Spring Boot applications begins with the dream of "code once, use everywhere," but can easily devolve into a maintenance nightmare if mishandled. The journey to a sustainable codebase requires deliberate decisions about what belongs in the repository. Features should only be shared when multiple projects face the same technical problem and standardization is collaboratively embraced. Developers must actively avoid moving business logic or unstable features into shared spaces to prevent bloated, abstract classes that continually require edge-case extensions. Structuring a shared library effectively means prioritizing ease of use and modularity. By leveraging Maven root configurations for dependency management and partitioning submodules (such as core abstractions, framework integrations, and auto-configurations), developers can opt into only the necessary functionality—avoiding the anti-pattern of bringing "the whole cow" when you just need a glass of milk.

Providing Spring Boot auto-configurations with specific conditional annotations ensures that client projects can gracefully override beans at the client or test level. Furthermore, using `@AutoConfiguration` instead of standard `@Configuration` avoids the performance overhead of Spring creating proxy interceptor classes for local method calls. Proper use of optional dependencies also ensures that libraries ship with only the requested classpath integrations without burdening client projects. For long-term maintainability, automated quality controls and discoverable documentation are essential. Tools like EditorConfig standardize codebase formatting, while ArchUnit proves invaluable for failing builds if package dependency cycles occur or if essential API annotations are missed. You can even configure ArchUnit to forcibly test if developers have read documentation by failing the build under specific conditions.

When establishing a versioning strategy, a pragmatic approach to semantic versioning coupled with build IDs often suffices for communicating changes clearly through a sensible changelog. Rather than enforcing top-down corporate mandates for library usage, teams should treat internal usage as a metric of quality. Successful shared components must be purposefully structured and effectively advertised to client projects, letting genuine demand organically drive internal adoption.

**Keywords:** building shared java libraries, spring boot autoconfiguration, maven dependency management, software modularity patterns, avoiding abstract business logic, conditional bean overriding, optional classpath dependencies, archunit structural testing, package dependency cycle prevention, editorconfig standardization, semantic versioning strategy, developer documentation best practices, internal tech adoption, micrometer tracing integration, backward compatibility maintenance

## Chapters

1. **Introduction to building shared Spring Boot libraries** (00:11) — An overview of the challenges and core agenda for developing sustainable shared packages.
1. **Determining when to extract code into a shared library** (03:15) — Specific indicators that code should be abstracted, such as repeated bug fixes and cross-project technical needs.
1. **Identifying logic to exclude from shared libraries** (05:15) — Why placing business logic and unstable features into a shared space leads to tightly coupled dependencies.
1. **Designing the global structure of a shared library** (07:41) — Establishing library structures with modular inclusion properties and standardized generic Maven configurations.
1. **Organizing code at the module and submodule levels** (10:48) — How to decouple framework-agnostic client logic from Spring-specific autoconfigurations and starter artifacts.
1. **Managing Spring configurations and bean definition overrides** (14:50) — Using autoconfiguration and conditional annotations to enhance performance and securely override context defaults.
1. **Enforcing code quality rules across client projects** (18:09) — Automating dependency cycle checks and standardized test formatting with tools like EditorConfig and ArchUnit.
1. **Creating discoverable and accessible library documentation** (20:17) — Best practices for writing explicit integration guidelines and code examples that assist junior developers.
1. **Streamlining contribution processes to aid maintainability** (21:32) — How straightforward setup routines encourage external collaboration and reduce maintaining overhead for authors.
1. **Applying semantic versioning and maintaining changelogs** (22:56) — Communicating library modifications effectively by mapping major and minor package revisions to explicit build IDs.
1. **Handling legacy versions and validating package builds** (25:19) — Why updating entirely to latest major versions ensures security patching while referential builds verify deployment safety.
1. **Encouraging shared library adoption through organizational advertising** (26:51) — Why advertising new internal tools verifies actual demand more efficiently than establishing strict enterprise usage requirements.

## Related Moments

- [Q&A on source code sharing and library coupling](https://www.wearedevelopers.com/videos/165-micro-frontends-with-module-federation-why-and-how) (from "Micro Frontends with Module Federation: Why and How?")
- [Sharing core dependencies for performance and team autonomy](https://www.wearedevelopers.com/videos/130-front-end-micro-apps) (from "Front-End Micro Apps")
- [Managing library dependencies and enforcing consistent code style](https://www.wearedevelopers.com/videos/1058-open-sourcing-a-library-how-hard-can-that-be) (from "Open sourcing a library: how hard can that be?")
- [Managing shared dependencies across isolated teams](https://www.wearedevelopers.com/videos/299-micro-frontends-anti-patterns) (from "Micro-frontends anti-patterns")
- [Simplifying solution structures and splitting shared projects](https://www.wearedevelopers.com/videos/100149-practical-tips-for-keeping-your-c-code-base-clean) (from "Practical tips for keeping your C# code base clean")
- [Structuring projects with Java and Spring Boot](https://www.wearedevelopers.com/videos/511-our-journey-with-spring-boot-in-a-microservice-architecture) (from "Our journey with Spring Boot in a microservice architecture")

## Related Articles

- [How to Avoid Over-Engineering](https://www.wearedevelopers.com/magazine/546-how-to-avoid-over-engineering)
- [The Future of Open Source: A Deep Dive - Scott Chacon at WeAreDevelopers World Congress 2024](https://www.wearedevelopers.com/magazine/471-the-future-of-open-source-a-deep-dive-scott-chacon-at-wearedevelopers-world-congress-2024)
- [The real reason we document our code](https://www.wearedevelopers.com/magazine/518-the-real-reason-we-document-our-code)
- [Using Java 17 latest features in real world projects](https://www.wearedevelopers.com/magazine/121-using-java-17-latest-features-in-real-world-projects)

## Related Jobs

- [Senior Software Engineer, Client Apps Platform](https://www.wearedevelopers.com/jobs/ext/1773893-senior-software-engineer-client-apps-platform) at **GitHub**
- [Senior Software Engineer](https://www.wearedevelopers.com/jobs/ext/15942-senior-software-engineer) at **GitHub**
- [Java Softwareentwickler - Spring Boot & Microservices](https://www.wearedevelopers.com/jobs/ext/1306817-java-softwareentwickler-spring-boot-microservices) at **Aok Systems Gmbh**
- [Senior Backend Engineer (Java)](https://www.wearedevelopers.com/jobs/ext/19369-senior-backend-engineer-java) at **Bonial International GmbH**
- [Principal Software Engineer, Database Infrastructure](https://www.wearedevelopers.com/jobs/ext/1465908-principal-software-engineer-database-infrastructure) at **GitHub**
- [Staff Developer Advocate, GitHub Security Lab](https://www.wearedevelopers.com/jobs/ext/1921051-staff-developer-advocate-github-security-lab) at **GitHub**