Quarkus: Supersonic Subatomic Java.

Spring Framework

Redis Java client

RabbitMQ Java client

Tutorials for using RabbitMQ in various ways

An annotation processor for generating type-safe bean mappers

An IntelliJ IDEA plugin for working with MapStruct

Apache Kafka - A distributed event streaming platform

Idiomatic persistence for Java and relational databases

Most popular Mocking framework for unit tests written in Java

A tool for mocking HTTP services

OpenAPI Generator allows generation of API client libraries (SDK generation), server stubs, documentation and configuration automatically given an OpenAPI Spec (v2, v3)

Library for OpenAPI 3 with spring-boot

A browser automation framework and ecosystem.

jsoup: the Java HTML parser, built for HTML editing, cleaning, scraping, and XSS safety.

WebDriver compatible driver for HtmlUnit headless browser.

Design patterns implemented in Java

Very spicy additions to the Java programming language.

Prometheus instrumentation library for JVM applications

Apache Commons Lang

vʌvr (formerly called Javaslang) is a non-commercial, non-profit object-functional library that runs with Java 8+. It aims to reduce the lines of code and increase code quality.

The official Java SDK for Model Context Protocol servers and clients. Maintained in collaboration with Spring AI

jOOQ is the best way to write SQL in Java

Flyway by Redgate • Database Migrations Made Easy.

The Java gRPC implementation. HTTP/2 based RPC

Cucumber for the JVM

An open-source, code-first Java toolkit for building, evaluating, and deploying sophisticated AI agents with flexibility and control.

The SDKMAN! Command Line Interface