Dan Vega

Spring Boot 4.2.0-RC1 is out: faster startup in executable jars, a properties migrator that can fail startup on warnings, and a new Ubuntu 26.04 buildpacks builder. Test it before GA. https://spring.io/blog/2026/10/23/spring-boot-4-2-0-RC1-available-now/

Spring AI 2.1.0-RC1: mark a tool with requiresConfirmation = true and the tool loop pauses until your app approves or denies the call. That's the guardrail you want before an agent touches real data. https://spring.io/blog/2026/10/23/spring-ai-2-1-0-RC1-available-now/

New Claude API version: 2026-10-21. temperature, top_p and top_k are gone. Send them and you get a 400, even at default values. If you set temperature in Spring AI options, check this before you upgrade. https://platform.claude.com/docs/en/api/migration-2026-10-21

Agent Skills now lives at the Agentic AI Foundation, next to MCP. 70+ agent platforms support it. One skill for your Spring conventions can work in Claude Code, Copilot and Cursor. https://www.anthropic.com/news/donating-agent-skills-to-the-agentic-ai-foundation

Oracle shipped an emergency Java fix for CVE-2026-91403 (CVSS 9.1). The JSSE flaw lets a network attacker pass forged TLS certs as trusted. Java 8 through 27 are listed. Patch your JDKs today. https://blogs.oracle.com/security/security-alert-cve-2026-91403-released

Jackson 3 rejected a null that my Boot 3 app had quietly turned into zero. I can see the case for the stricter default. But existing clients may rely on the old behavior. Would you preserve that contract or ask clients to change? https://youtu.be/HiPkoGTeNJc

What actually breaks when you move to Spring Boot 4? I upgrade a real app from 3 to 4 on camera. No slides. Just fixing compiler errors, broken tests, and changes that don't trigger a warning. https://youtu.be/HiPkoGTeNJc

I built an app to get ideas out of my head. It's called Clearing. It replaced a handful of tools I used to stitch together. There's research behind this. Unfinished tasks keep pulling at your attention until you write down a plan for them. Capture it. Plan it. Let it go.

Tim Ferriss won't let AI write his next book. His reason: “If I do that, I'm done.” He still uses it for everything around the writing. Developers need the same line. Pick the skills you want to keep in your head. Do those by hand. Hand off the rest. https://youtu.be/X9nfEE8DJeI

Claude Code edits my YouTube videos. Not the code in them. The videos. Transcribe. Cut dead air. Zoom the jump cuts. Lower third. Sound effects. Music. Then a Premiere timeline. Each step is a skill. Most asked question at dev2Next this week. What would you hand it first?

I made a theme for IntelliJ. Kiln is warm charcoal and cream with a clay accent and calm syntax colors. Dark and light, built on the new Islands look. It's an early release, and I'd love feedback before it goes on the Marketplace. https://github.com/danvega/kiln-theme

Fetching JSON from an API and mapping it to records in plain Java. No Jackson. No Gson. No dependencies. Just HttpClient and the new JSON API coming in JDK 28 (JEP 540). 👀 https://github.com/danvega/native-json-demo

Spring AI 2.1.0 M1 is out. What stands out to me is support for OpenAI's Responses API. https://spring.io/blog/2026/09/25/spring-ai-2-1-0-M1-available-now

Spring Boot 3.5 open source support ended June 30, 2026. If you're on 3.x, this upgrade is coming. I took a real Spring Boot 3.5 app to 4.1 live. No slides. The missing H2 console, Jackson 3, and JSpecify null safety. Every break fixed and explained. https://youtu.be/HiPkoGTeNJc

Spec-driven dev tools feel like overkill for one person. So I wrote down the plan I already use as a handful of skills. Then I built a Spring Boot store with Stripe checkout. 57 tests, all green. A retro after every build edits the skills. https://youtu.be/bHJZiM2XM-w

Spring AI now has an official TypeSafe project. We build a model router from an empty app in 4 classes on one dependency. Send a prompt, get back which tier answers (luna, terra, sol, or astra) plus a confidence score in about 300ms. https://youtu.be/_5V6sJxRgqk

You're not behind on AI coding agents. You just need three basics to start with Claude Code: the loop, the permission prompt, and context. Everything else can wait. https://youtu.be/BiKxFmirPpw

An AI that doesn't generate text. It decides. Three apps built with Jev: - Sort 100 comments in seconds - Grade your blog draft as you type - Pick the right model before a token streams All buildable this week. https://youtu.be/vMpPDJ3bwXI

Six files to one line. I turned last week's hand-rolled Jev client into a Spring Boot 4 starter. Add the dependency, set one env var, inject JevClient, get typed answers. Then we open the starter to see how auto-configuration, conditions, and the imports file work. https://youtu.be/fq_nYo4BnrY

Jev doesn't generate text. It answers typed questions in about 100ms. One RestClient, one endpoint, and a messy support message returns three typed answers. No prompt. No JSON parsing. Here's how to call it from Spring Boot 4. https://youtu.be/K4rqR6hcsAo

Flip one flag and the user call fails at 200ms. The Future version still takes a full second. The StructuredTaskScope version returns in 200ms and interrupts the orders call on the spot. Same method, 3 ways, on the JDK 27 API. https://youtu.be/Nl-a4ukWodk

8 months. 309 commits. 8 months. 309 commits. 80,000+ lines of code. . I built the Spring Boot app that runs my whole YouTube channel. The scary part: Claude doesn't just build it, it operates the app too through its MCP server. Here's how. https://youtu.be/9O-E7DAfYrE

Skills aren't just for coding. I drop in one raw podcast recording. Four Claude Code skills turn it into an mp3, a transcript, a description on my clipboard, and a spring.io PR. No manual steps. Anything you repeat is a workflow. This is where I start. https://youtu.be/q3Fk6ADuaSI

Real .cfm templates running inside Spring Boot 4. cfoutput, cfif, and cfloop all render in the browser. The trick is one property that flips the BoxLang starter into its ColdFusion parser. It even runs on port 8500. https://youtu.be/CLzEQ1Gtqy4

Huge Thank you to @dthompsondev.bsky.social for joining us on Spring Office Hours this week. It was a fun conversation and Danny is what we should aspire to be. Great person and can't wait to catch up with him at Commit Your Code in a couple of weeks! www.youtube.com/watch?v=Jzbx...

Boris, the creator of Claude Code, mapped out 5 steps of AI adoption. Find out which step you're on and what it takes to level up. https://youtu.be/g12mC2J11d0

This week's newsletter is out. New videos on Docker Compose and Spring AI guardrails, plus a first look at the Spring Boot 4 crash course I'm working on. Be the first to know when the course is released. Subscribe: www.danvega.dev/newsletter/

I caught my AI making three mistakes in a Spring Boot app I know cold. An hour later it gave me Swift code I shipped without blinking. Same model. The code I should trust less felt better. Here's why that happens. https://youtu.be/UuM2-nRsLuA

Outdated dependencies are an easy target for attackers. AI can help you upgrade them the right way. This video shows when to reach for AI and how to approach the upgrade safely. https://youtu.be/MYtia9xsTrQ

A system prompt is not a security layer. I built 4 Spring AI safeguards (scope restriction, keyword blocking, output leak detection, PII masking) and show what each one catches and misses. Every one can be bypassed alone. Layer them: https://www.youtube.com/watch?v=EZ6Uh1-8Ui4

That docker-compose.yml sitting in every Java repo confuses a lot of people. It's not about putting your app in a container. It runs the stuff your app needs, like Postgres, so any project just runs when you clone it. Clone. Run. Done. https://youtu.be/0LNVXHKKJb8

Spring AI 2.0 replaces per-model tool loops with a composable ToolCallingAdvisor in the ChatClient chain. Watch it run live: stream tool-call events into a "Calling tool..." UI, then take manual control when you need it. https://youtu.be/g6IhOsFKM7c

How long does one YouTube video really take? I mapped every stage from "I have an idea" to published, repurposed, and promoted. Turns out it's 10 stages across 3 phases, and AI now handles the mechanical parts. https://www.danvega.dev/blog/content-creation-workflow

Embabel 1.0 is here. Rod Johnson's AI agent framework for the JVM hit GA: stable APIs, everything on Maven Central, RAG promoted to production, new model integrations, and better MCP citizenship. Builds on Spring AI, Spring Boot 3.5, Java 21. www.danvega.dev/blog/embabel...

Spring AI 2.0 moved the tool calling loop into the advisor chain. That means you can hook into it and watch it run. I built a streaming chat where every tool call shows up live as a pill, "Calling getWeatherForecast...", using one small custom advisor. github.com/danvega/tool...

LLMs don't always return valid structured output. Spring AI 2.0 can now detect malformed responses and retry automatically until you get clean, parseable data. Here's how self-correcting structured output works: https://youtu.be/vxOeeNyOtZY

Can you use Java for AI? Yes. And if you're building AI into real applications instead of training models, it might be the better choice. The training era belonged to Python. The integration era looks a lot like the JVM. www.danvega.dev/blog/can-you...

AI agents connecting to Slack, GitHub, Jira, and MCP servers can easily hit 50+ tools. That's 55K+ tokens gone before any conversation starts, and accuracy drops fast. Spring AI's tool search solves this. https://youtu.be/VG00DildlvY

Spring AI advisors are AOP for your LLM calls. Do something before the request, something after. I built two custom advisors: one that logs which tools are visible to the model, and one that tracks token usage per call with a running total. Full walkthrough here: youtu.be/WNJFR-_N9bc

You've seen AI generate ugly UI. The team behind Tailwind CSS and Refactoring UI built a set of agent skills that actually produce great-looking interfaces. Design, ideation, and more, all broken into focused skills. Here's a walkthrough. https://youtu.be/-B7uyMp54S4

Register 47 tools in Spring AI and every one ships its JSON schema on every request. That's ~5,000 prompt tokens before the user asks anything. The Tool Search Advisor fixes it: the model sees ONE search tool. Demo + walkthrough 👇 (Video Coming Soon) github.com/danvega/spring-ai-tool-search

Spring AI has two APIs for working with LLMs: ChatClient and ChatModel. They're not interchangeable, and knowing when to use each one will save you time and confusion. https://www.youtube.com/watch?v=IdIDI71sGZM

X just released their MCP Servers and you can wire them up with Spring AI. Here's a walkthrough to get you started. https://youtu.be/j4chxGtqkY8

Spring Boot 4.1 introduces @RedisListener, a much simpler way to subscribe to Redis messages. If you've dealt with the old MessageListener setup, you'll appreciate this. https://youtu.be/lMbgBYlUtfc

Episode 8 of Fundamentals of Software Engineering just dropped. Nate and I talk open source sustainability, what AI tooling actually looks like in practice, and the coming token crisis you should be thinking about now. Catch the recording here👇🏻 https://youtu.be/kaY8uvnbfis

Spring Boot 4.1 now includes built-in SSRF protection for HttpClient. No extra libraries, no custom filters. Secure by default. https://youtu.be/PDbBG_GrcwU

Spring Boot 4.1 brings lazy JDBC connections. Your app won't grab a database connection until it's actually needed. This means fewer wasted resources and better scalability out of the box. https://youtu.be/lsaBN1U2EB8

Spring Boot 4.1 brings first-class gRPC support. Here's how to get started with Spring gRPC from scratch. https://youtu.be/MPHuBNqbYPM

Spring Boot 4.1 added a property: spring.datasource.connection-fetch=lazy Transactional methods grab a connection the moment they open, even when they never query. Cache hit, early return, slow API call. That connection sits idle. Lazy waits for a real statement. github.com/danvega/jdbc...

Most developers reach for a message broker the second they need reliable events. You might not need one. Spring Modulith ships with a durable event registry that persists events right to your database. Here's how to use it. https://youtu.be/KLX9ulb2AfM