Troubleshooting Articles
4 articles about Troubleshooting. Explore Spring Boot implementation, design, and operations across related topics.
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Causes and Fixes for HikariCP "Failed to validate connection" and "Connection is closed" in Spring Boot - How to Decide maxLifetime and keepaliveTime
Learn how to isolate HikariCP "Failed to validate connection" and "Connection is closed" errors by pool stage, how to derive maxLifetime and keepaliveTime from DB and network timeouts, and how to diagnose why the pool does not recover after a DB restart.
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Why @Transactional, @Cacheable, and @Async Don't Work in Spring Boot - Understanding AOP Proxies and Self-Invocation to Fix It
@Transactional doesn't roll back, @Cacheable hits the DB every time, @Async runs synchronously. All of these are caused by how Spring AOP proxies work. This article isolates five patterns - self-invocation, private/final methods, new, and missing enablement - with reproducible code and diagnostic steps, then compares workarounds such as extracting to a separate Bean, self-injection, and TransactionTemplate.
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How to Fix LazyInitializationException in Spring Boot + JPA - Causes and Solutions for "could not initialize proxy - no Session"
Solve the LazyInitializationException (could not initialize proxy - no Session) that crashes the moment you access a lazily-loaded association in Spring Data JPA, working backwards from how Hibernate sessions and transaction boundaries operate. Compares the four proper approaches—JOIN FETCH, @EntityGraph, DTO projection, and @Transactional—and provides criteria for making decisions without resorting to open-in-view=true or switching to EAGER.
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Spring Boot Application Won't Start? How to Isolate the Cause and Fix It
For anyone panicking at 'APPLICATION FAILED TO START'. Targeting Spring Boot 3.x, this guide walks through 7 typical patterns, including port conflicts, duplicate Beans, circular references, missing DataSource configuration, and profile mistakes, using a symptom-first reverse lookup. It also covers how to read FailureAnalyzer messages and how to use the --debug flag, with real examples.