Spring Boot — convention-over-configuration framework for building Spring-based Java applications
A complete guide to testing REST APIs with JUnit 6 using both MockMvc and WebTestClient. Covers GET, POST, PUT, DELETE testing, JSON path assertions, validation error testing, file uploads, authentication, and a matcher quick-reference table.
A complete guide to testing Spring Boot applications with JUnit 6. Covers unit tests with plain JUnit, slice tests (@WebMvcTest, @DataJpaTest, @JsonTest), full integration tests with @SpringBootTest, context caching, Testcontainers, and best practices for each layer.
@RestClientTest and MockRestServiceServer, rebuilt against Spring Boot 4.1.1: a RestClient-based client, a legacy RestTemplate client, a declarative HTTP interface client, and the error path -- plus three real, verified surprises: two packages that moved without warning, Jackson 3 resolving in place of Jackson 2 by default, and a genuine trap where identical mocking code works for RestTemplate and throws a real AssertionError for RestClient.
Are you ready to move your data layer into the future? Configuring Hibernate 7 with Spring Boot 4 represents a significant milestone in the Java ecosystem. Spring Boot 4 (released November 2025) aligns with Jakarta EE 11 APIs, and Hibernate 7 introduces native JSON support and refined type systems — so developers are encountering new challenges, from namespace migrations to modern JVM targets (the baseline is Java 17, with Java 21 or 25 recommended for virtual threads). If your application feels stuck in the past, this guide is your roadmap to the cutting edge. In this deep-dive guide, we’ll explore the high-performance world of Spring Boot 4. We will cover the mandatory shifts in Jakarta Persistence 3.2, advanced performance tuning for virtual threads, and how to leverage Hibernate 7’s modern features to ensure your application on ankurm.com is ready for the evolving landscape of 2026 and beyond. The Problem: Legacy Debt in a Modern World Many applications are still tethered to the legacy javax.* namespace or older Hibernate versions that lack the efficiency of modern JVM features like Project Loom (Virtual Threads). Using outdated configurations leads to "Namespace Collision" errors and missed opportunities for the significant memory and performance optimizations anticipated in modern runtime environments. The Agitation: The Risk of Stagnation As Java moves toward the anticipated widespread adoption of Java 21 and the eventual standard of Java 25, staying on Spring Boot 2 or 3 becomes an increasing security and performance liability. Hibernate 7 introduces breaking changes in how it handles specific database dialects and type mappings. Failing to plan your migration now could lead to technical debt, incompatible libraries, and a data layer that cannot fully leverage modern hardware. The Solution: Harnessing Spring Boot 4 & Hibernate 7 Spring Boot 4 is built for speed, native compilation (GraalVM), and seamless integration with Hibernate 7. By migrating to the jakarta.persistence namespace and leveraging the "Unified Type System" introduced in Hibernate 7, we can build data layers that are significantly leaner and more performant.
GraalVM native-image compiles a Spring Boot 4.1 app into a binary that starts in 0.09 seconds instead of 3.5 -- but only after a real ClassNotFoundException, a fix using the tracing agent, and a metadata-collision trap that silently undoes that fix. Rewritten with verified Boot 4.1.1 and current GraalVM versions, honest costs, and where Project Leyden fits as the non-native alternative.