How to Build RAG with Spring AI and pgvector: Full Tutorial 2026 Every large language model has a hard cutoff. Ask it about your company's internal onboarding policy, a document uploaded yesterday, or last week's product release, and it either admits it does not know or, worse, makes something up that sounds confident and correct. Your LLM cannot answer questions about last week's internal policy update, your product's latest release notes, or a PDF sitting in your company's document store. It only knows what it was trained on. RAG fixes that by handing the model your own data at query time, and Spring AI makes the whole pipeline buildable in plain Java. What You Will Learn A Retrieval-Augmented Generation application built with Spring AI