macrozheng

Jan 22, 2026 · Backend Development

Mastering Java SPI: Build a Pluggable Authentication System with Spring Boot

This guide explains Java's Service Provider Interface (SPI) mechanism, compares it with APIs, and walks through creating a multi‑module Maven project that defines SPI interfaces, implements plugins, loads external JARs with a custom class loader, and integrates the plugins into a Spring Boot application for dynamic authentication.