Spring Boot 4: @JsonComponent Silently Stops Working
Upgraded to Spring Boot 4 and your @JsonComponent went quiet? Jackson 3 took the HTTP layer without telling you. Here's the exact mechanism and the real fix.
spring-boot-errors
4 PostsBinding to target ... failed: two bugs, one identical banner
BindValidationException and UnboundConfigurationPropertiesException print the exact same Spring Boot startup banner. Here's how to tell which broke your app.
APPLICATION FAILED TO START, and When You Don't Get It
Spring Boot's failure banner only shows up when one of ~40 built-in analyzers recognizes your exception. Here's the catalog, and what prints when none do.
TestRestTemplate's NoSuchBeanDefinitionException in Spring Boot 4
Boot 4 quietly stopped auto-wiring TestRestTemplate and MockMvc in @SpringBootTest, and the @MockBean-to-@MockitoBean rename hides a sneakier trap of its own.