Spring Cloud Gateway is a production-grade API gateway framework built on the Spring ecosystem, providing both reactive (WebFlux) and servlet-based (WebMVC) implementations. It routes HTTP/HTTPS/gRPC/WebSocket traffic through a configurable chain of predicates and filters, supporting features such as path rewriting, header manipulation, rate limiting (Redis/Bucket4j), circuit breaking (Resilience4J), retry with backoff, response caching, load balancing, and distributed tracing (Micrometer/OpenTelemetry). The architecture is plugin-based: route predicates and filter factories are registered as Spring beans and composed via a fluent builder DSL or YAML/properties configuration. External dependencies include Project Reactor, Spring Cloud Load Balancer, Redis, and optional integrations with gRPC, OAuth2, and serverless functions. The codebase is organized into multiple Maven modules: the core server modules (spring-cloud-gateway-server-webflux and spring-cloud-gateway-server-webmvc) contain the routing engine, filter/predicate factories, and auto-configuration; proxy exchange modules provide lightweight annotation-based proxying; and integration tests cover HTTP/2, SSL, WebSocket, and gRPC scenarios. Key entry points include FilteringWebHandler (WebFlux) and GatewayRouterFunctions (WebMVC) for request processing, RoutePredicateHandlerMapping for route matching, and GatewayAutoConfiguration for bean wiring. The system is designed for extensibility: custom filters and predicates can be added by implementing GatewayFilter or RoutePredicateFactory and registering them as beans. Data flows follow a standard gateway pattern: an incoming request is matched against route definitions (loaded from properties, Redis, or service discovery), then passed through a chain of global filters and route-specific filters. Filters can modify the request/response, cache bodies, enforce rate limits, or invoke circuit breakers before forwarding to the backend via a configurable HTTP client (Netty-based for WebFlux, RestTemplate/WebClient for WebMVC). Observability is embedded via Micrometer metrics and OpenTelemetry tracing, with custom observation conventions for gateway-specific events.
Discord4J is a reactive, modular Java library for building Discord bots. It provides a high-level abstraction over Discord's REST API, Gateway WebSocket, and Voice protocols, built on Project Reactor and Netty. The library is structured into separate modules: `common` (shared utilities, store abstraction, rate limiting), `rest` (HTTP client with rate limiting and retry), `gateway` (WebSocket client with state management), `core` (domain objects, event system, spec builders), `voice` (voice connection with encryption and DAVE protocol), and `oauth2` (OAuth2 authentication). The architecture follows a layered design with pluggable components for caching (StoreLayout), rate limiting (GlobalRateLimiter), serialization (ExchangeStrategies), and event dispatching. The codebase demonstrates strong software engineering practices: extensive use of immutable specs via the Immutables library, reactive streams for all I/O, and a comprehensive event hierarchy mirroring Discord's API. However, it contains a mix of deprecated legacy specs and newer immutable specs, some experimental features, and a few duplicated utilities. Overall, it is a well-crafted, production-ready library with active maintenance and good reusability in its core patterns.
hsweb-framework is a modular Java backend development framework, not a single deployable application. It is built as a multi-module Maven monorepo providing reactive-first CRUD scaffolding, RBAC/authorization, an OAuth2 authorization server, dynamic datasource switching, reactive caching, access logging, i18n, dictionary/enum support, and file upload services. The code is dominated by Spring Boot auto-configurations, SPI extension points, and reusable controller/service interfaces that applications consume as dependencies. It supports both WebFlux (R2DBC) and WebMVC (JDBC) stacks, with reactive APIs as the primary design direction. Architecturally, the framework centers on hsweb-core (bean utilities, i18n, exceptions, ID generation), hsweb-commons (generic CRUD services/controllers, query helpers, SQL analysis), hsweb-authorization (authentication model, token management, AOP method authorization, OAuth2 granters/authenticators), hsweb-datasource (dynamic schema/table/datasource switching), hsweb-concurrent-cache (ReactiveCache with Guava/Caffeine/Redis backends), hsweb-logging (AOP access logs), and hsweb-system (default user, permission, dictionary, and file modules). Key entry points are Java annotations such as @Authorize, @Resource, @EnableEasyormRepository, @EnableEntityEvent, and interface contracts like ReactiveServiceCrudController and CrudService, which auto-generate REST endpoints for entities. Primary data flows move from HTTP requests through WebFlux/WebMVC controllers into reactive or synchronous CrudService implementations, then through EasyORM repositories to R2DBC/JDBC databases. Authorization flows are layered: token parsing/generation, AuthenticationManager initialization, AOP authorization definition parsing, data-permission handlers, and OAuth2 grant/redirect handling. Entity lifecycle events, cache invalidation, and query rewriting are cross-cutting mechanisms implemented via Spring application events, Reactor context, and JSqlParser-based SQL analysis. Redis is used for token storage and cache synchronization; Caffeine/Guava support local reactive caches. External dependencies include Spring Boot 3.x, Reactor, R2DBC, JDBC, Redis, JSqlParser, and Javassist. The codebase demonstrates strong engineering in isolated utilities like FastBeanCopier, reactive cache invalidation, streaming JSON response writing, and SQL query analysis. However, it carries notable drift: mixed javax/jakarta annotations, deprecated legacy APIs, a coexistence of servlet and reactive paths, some ignored/incomplete tests, and complex compatibility layers around OAuth2 and cache semantics. Overall it is a mature, actively maintained framework with substantial reusable components, though consumers should expect to navigate Chinese-language comments and some legacy baggage.