Keycloak is a production-grade open-source Identity and Access Management (IAM) server. In production it provides authentication and authorization for applications via OIDC/OAuth2, SAML, and emerging standards including OID4VC verifiable credentials (SD-JWT, mdoc, LDP), Shared Signals Framework (SSF/CAEP/RISC), WebAuthn passkeys, and CIBA. The server is a modular Java monolith running on Quarkus, exposing REST admin APIs (v1 plus a feature-gated v2), protocol endpoints, and React-based admin/account consoles, with a Kubernetes operator for managed deployment and CLI tools (kc.sh, kcadm.sh, kcreg.sh). The architecture is built around a pervasive SPI/provider-factory pattern: nearly every subsystem (authentication flows, password hashing, event listeners, user storage federation, token introspection, crypto providers, theme selection) is pluggable via ProviderFactory + Spi interfaces, making the system highly extensible. Persistence uses JPA/Hibernate with Liquibase migrations across PostgreSQL, MySQL, MariaDB, Oracle, and MSSQL; distributed caching and cluster events use Infinispan. The codebase also ships Java and TypeScript admin client libraries and legacy WildFly SAML adapters. Primary data flows: browser/device authentication flows produce signed tokens (access, refresh, ID, userinfo) via pluggable crypto providers (BouncyCastle, FIPS 140-2, Elytron); user/session state flows between the database and Infinispan caches with invalidation events; identity brokering federates users from LDAP, Kerberos, and social IdPs; admin operations emit admin and audit events. Test infrastructure is extensive: a new JUnit 5 test framework with DI annotations coexists with a legacy Arquillian suite (migration in progress), plus Playwright e2e tests for the admin UI. This is purely an application repository - no data pipelines or research artifacts. Notable reusable components include a self-contained SD-JWT implementation, a JOSE/JWS/JWK library, and generic utilities (PathMatcher, Retry) that could be extracted into other Java projects with minimal modification.
Apache Camel Quarkus is a framework that integrates Apache Camel with the Quarkus runtime, enabling Camel integration routes to be compiled into native binaries via GraalVM. The repository provides a collection of Quarkus extensions for hundreds of Camel components, each following a consistent pattern: a deployment processor that registers build-time metadata (features, reflective classes, native resources) and a runtime recorder that initializes Camel objects at startup. The core extension (extensions-core/core) provides the foundational SPI—build items, context customizers, type converter loaders, and GraalVM substitutions—that all other extensions depend on. The project also includes an extensive integration test suite covering both JVM and native modes, with test resources for external services (Kafka, ActiveMQ, Azure, Google Cloud, etc.) and conditional test execution based on platform or environment. Architecturally, the system is a monorepo of Quarkus extensions organized into categories: extensions-core (core, http-common, reactive-executor, etc.), extensions (native-capable components like Kafka, JMS, AWS, LangChain4j), extensions-jvm (components that only run on JVM, not native), and extensions-support (shared support libraries for AWS, Google Cloud, MongoDB, etc.). Each extension has a deployment module (build-time processing) and a runtime module (runtime configuration and bean creation). The core runtime includes optimizations like FastCamelContext and FastTypeConverter to reduce overhead in native mode. Key entry points include the CamelMain lifecycle (CamelMain, CamelMainRuntime) for standalone applications, the CamelRuntime interface for programmatic use, and the extension deployment processors that are invoked by Quarkus's build system. Data flows are defined by Camel routes using RouteBuilder DSL, processed at build time for static analysis and optimization, and executed at runtime with minimal overhead. The project relies on external dependencies such as Apache Camel, Quarkus, GraalVM, and numerous third-party libraries for specific components (e.g., AWS SDK, Azure SDK, Kafka clients). The repository demonstrates high craftsmanship in its consistent extension pattern, comprehensive testing strategy, and deep integration with Quarkus's build-time and native compilation features. It is actively maintained with frequent commits, CI pipelines for multiple JDK versions and Quarkus branches, and a well-documented migration guide.
Redisson is a feature-rich Java client for Valkey and Redis that extends basic key-value storage with distributed Java collections, objects, and services. It provides synchronous, asynchronous, and reactive APIs for Redis operations, along with integrations for popular frameworks like Spring, Micronaut, Quarkus, and Hibernate. The library implements advanced Redis features including streams, geo-spatial indexing, pub/sub, bloom filters, and distributed computing primitives. Its architecture features a clean separation between core Redis protocol handling, codec-based serialization, and framework-specific adapters, making it a versatile tool for building distributed applications with Redis as a backend.
Apache Polaris is a production-grade, multi-tenant Iceberg REST catalog server built on Quarkus. It provides a REST API for catalog management (namespaces, tables, views), credential vending for cloud storage (S3, GCS, Azure), fine-grained authorization via built-in RBAC or external OPA/Ranger, and event publishing (Kafka, CloudWatch). The system supports two persistence backends: a legacy relational JDBC (PostgreSQL, H2) and a new NoSQL abstraction with custom indexing, caching, and distributed invalidation. Multi-tenancy is implemented via isolated realms, each with its own configuration and persisted state. Key entry points are the Quarkus server (`polaris-server`), a CLI admin tool, and a Python client. External dependencies include Iceberg libraries, Quarkus, Jackson, Testcontainers, and optional integrations like Open Policy Agent, Apache Ranger, and Kafka. The architecture is modular with clear SPI boundaries, making extensions (persistence, auth, federation) pluggable.
Eclipse Hono is a cloud-native IoT messaging platform that ingests telemetry and events from devices via multiple protocols (MQTT, CoAP, HTTP, AMQP, LoRa, Sigfox) and routes them to northbound applications over AMQP, Kafka, or Google Pub/Sub. The codebase is modular, comprising protocol adapters, device registry services (JDBC and MongoDB), authentication, command routing, and client libraries. It is built on Vert.x and Quarkus, uses Micrometer for metrics and OpenTracing/OpenTelemetry for distributed tracing. The system handles device registration, credentials management, tenant configuration, connection limits, and resource governance. It includes a CLI tool for consuming telemetry and a comprehensive integration test suite. The repository is actively maintained with frequent commits and CI pipelines.
Dekorate is a Java annotation-processing framework that generates Kubernetes, OpenShift, Knative, and other container orchestration manifests at compile time. It is primarily a library consumed by Java applications, especially those built with Spring Boot, Quarkus, Thorntail, or plain Java. The architecture centers around a `Session` that coordinates `ConfigurationGenerator`s, `ManifestGenerator`s, and a graph of `Decorator`s to produce deployment descriptors. It supports multiple platforms via separate annotation modules (e.g., kubernetes-annotations, openshift-annotations, knative-annotations) and integrates with build tools like Docker, Jib, S2I, and Tekton for CI/CD pipelines. The codebase is well-structured with clean abstractions (Decorator, Configurator, SPI factories) and extensive testing, though it suffers from a high module count and some outdated dependencies (e.g., Java 1.8 baseline, old Spring Boot versions in examples). Overall, it is a mature and capable tool for generating Kubernetes manifests from Java annotations.
This repository is a comprehensive collection of example applications for the Apache KIE ecosystem, specifically Kogito, Drools, and jBPM. It demonstrates how to build cloud-native business automation services using DMN decision models, PMML predictive models, DRL rules, and BPMN process orchestration. The examples are structured as runnable microservices for both Quarkus and Spring Boot runtimes, covering a wide range of capabilities including event-driven messaging with Kafka, persistence with PostgreSQL/MongoDB/Infinispan, security with Keycloak OIDC, monitoring with Prometheus/Grafana, and deployment on Kubernetes/OpenShift. The repository serves primarily as a learning and demonstration resource, not as a production library. It features high duplication across the two runtime stacks, with many near-identical examples maintained in parallel. The code is functional and follows standard Kogito patterns, but the emphasis is on showcasing features rather than providing reusable, production-grade components. Some examples use snapshot versions and older infrastructure configurations, indicating active development but also potential drift.