When you think of Java modularity, chances are your first thoughts land on JPMS, or perhaps on Spring’s flexible configuration model. For those who 'experienced' like me, thought can reach OSGI specification or other stacks like Vert-X. Yet long before either, Java offered a minimal yet powerful mechanism for loose coupling: ServiceLoader.   In this article, we’ll explore what ServiceLoader is, how it works under the hood, what its limitations are, and how to use it effectively in a modern Java e

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A Java geek

ServiceLoader is Java's built-in Service Provider Interface (SPI) mechanism introduced in Java 6, enabling loose coupling through capability discovery rather than just plugin loading. The article explains how ServiceLoader works internally through lazy instantiation via META-INF/services configuration files, its integration with JPMS modules in Java 9+, and practical patterns for versioning and negotiation. It addresses the main limitation of requiring no-argument constructors and provides workarounds using factory patterns and proxies. The guide demonstrates Spring Boot integration using ServiceListFactoryBean and advocates using ServiceLoader at library boundaries while reserving dependency injection frameworks for application wiring.

Rediscovering Java ServiceLoader: Beyond Plugins and Into Capabilities