Spring Boot
Convention-over-configuration on top of Spring Framework. Phil Webb + Dave Syer, 2014. Starters + auto-configuration + embedded server = one jar → production.
Revolutionized Java enterprise: no XML, no application server deploy, no "where does my main() method go". @SpringBootApplication annotation. Starters: spring-boot-starter-web pulls in Tomcat + Jackson + Spring MVC. Boot 3 (2022) requires Java 17+, has AOT support via GraalVM. Spring Initializr (start.spring.io) generates starter projects. Competitor: Quarkus (Red Hat, native-first), Micronaut, Helidon. Boot is still the default choice in Java enterprise in 2025.