This repository is a comprehensive multi-module Maven project that serves as a learning and demonstration resource for the Java ecosystem, specifically focusing on Spring Boot, microservices, middleware, and AI integration. It contains over 20 independent modules, each showcasing a specific technology or pattern: from core Spring features (AOP, events, lifecycle) to advanced distributed systems (Dubbo, gRPC, Netty, RocketMQ, Kafka, Redis, Elasticsearch, ShardingSphere, Sentinel, Nacos, Curator) and modern AI capabilities (LangChain4j-based RAG, agentic workflows, guardrails, MCP client, image generation, TTS). The architecture is a modular monolith where each module is independently runnable via its own Spring Boot application class, sharing a common utility library (whatsmars-common) for serialization, caching, consistent hashing, encryption, and logging. The AI module is particularly notable for implementing advanced patterns such as query compression, smart routing, re-ranking, structured output, and configurable agentic workflows (sequential, parallel, conditional, loop, supervisor). While the repository is not a single deployable product, it provides high-quality, well-documented examples that demonstrate non-obvious craftsmanship in areas like custom gRPC load balancing, consistent hashing with virtual nodes, and programmatic logger creation. The codebase is professionally written with good separation of concerns, though testing coverage is limited to utility classes. Overall, it is a valuable reference for Java developers exploring modern frameworks and AI integration patterns.