Dan Vega

Practical writing on Java, Spring, AI, and the craft of software engineering.

If you're building with Java and Spring (or trying to figure out where AI fits into your development workflow) you're in the right place. I write practical, beginner-friendly deep dives on Spring Boot, Spring AI, and software engineering fundamentals, collected here in chronological order.

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MockMvcTester vs RestTestClient: Which one Should You Use in Spring Boot 4?
· 23 min read

MockMvcTester vs RestTestClient: Which one Should You Use in Spring Boot 4?

A comparison of MockMvcTester and RestTestClient for testing Spring Boot web applications, exploring when to use each approach and their key differences.

Spring JMS Client: A Complete Guide to JmsClient in Spring Boot 4
· 17 min read

Spring JMS Client: A Complete Guide to JmsClient in Spring Boot 4

Master the Spring JMS Client with this complete Spring Boot 4 JmsClient tutorial. Learn when to choose JMS over Kafka, configure message conversion, and send messages using Spring's fluent API.

Spring Data AOT Repositories: Faster Startup and Build-Time Query Validation
· 15 min read

Spring Data AOT Repositories: Faster Startup and Build-Time Query Validation

Learn how Spring Data AOT Repositories move query processing from runtime to compile time, reducing startup times and memory usage, plus how to validate repository methods at build time.

Spring Boot 4: Everything You Need to Know (4.0 and 4.1)
· 33 min read

Spring Boot 4: Everything You Need to Know (4.0 and 4.1)

Everything new in Spring Boot 4 and 4.1, from null safety and HTTP interfaces to modularization and gRPC, plus the upgrade path from Spring Boot 3.

Native Retry Support in Spring Boot 4: No External Dependencies Required
· 28 min read

Native Retry Support in Spring Boot 4: No External Dependencies Required

Spring Boot 4 includes native retry support with @Retryable, RetryTemplate, and @ConcurrencyLimit. Learn how to add resilience without the spring-retry dependency.

Jackson 3 in Spring Boot 4: JsonMapper, JSON Views, and What's Changed
· 28 min read

Jackson 3 in Spring Boot 4: JsonMapper, JSON Views, and What's Changed

Learn how to use Jackson 3 in Spring Boot 4 with the new JsonMapper, immutable configuration, unchecked exceptions, and JSON Views with the hint() method.

HTTP Interfaces in Spring Boot 4: Say Goodbye to Boilerplate
· 19 min read

HTTP Interfaces in Spring Boot 4: Say Goodbye to Boilerplate

Learn how HTTP interfaces let you define declarative HTTP clients in Spring Boot, and discover how Spring Framework 7 eliminates the configuration boilerplate with @ImportHttpServices.

Java
· 22 min read

Stop NullPointerExceptions Before Production with Spring Boot 4's Null Safety

Discover how Spring Boot 4 and JSpecify annotations catch NullPointerExceptions at compile-time instead of runtime. Learn to implement @NullMarked and @Nullable for bulletproof Java code with practical examples.

Spring Boot 4's Bean Registrar: A Cleaner Way to Register Beans Programmatically
· 12 min read

Spring Boot 4's Bean Registrar: A Cleaner Way to Register Beans Programmatically

Learn how Spring Boot 4's new BeanRegistrar interface simplifies programmatic bean registration in Spring Framework 7. This tutorial demonstrates dynamic bean creation based on environment properties, conditional registration with complex logic, and performance optimization techniques. Discover when to use BeanRegistrar vs @Bean annotations with practical code examples and testing strategies...