The Factory Method pattern lets subclasses decide which object to create, eliminating if/else creation logic and making your codebase open for extension without modification. Complete guide with runnable Java examples, JDK usage, Spring Boot integration, pitfalls, and FAQs.
Of every breaking change in the Spring Boot 2 → 3 era, the removal of WebSecurityConfigurerAdapter generated the most confused stack traces I've debugged — because security configuration is the one place where "it compiles and runs" tells you almost nothing about whether it still protects anything. This guide migrates Spring Security 5 configurations to the 6.x component model (Spring Boot 3.x), covers what tightens further in Spring Security 7 (Spring Boot 4), and flags the places where a mechanical conversion quietly changes your authorization behaviour.
Spring Boot 4 finally forced the issue: RestTemplate, in maintenance mode since Spring 5, is out of the recommended path, and codebases full of getForObject() and exchange() calls need a plan. The good news is that RestClient (introduced in Spring 6.1 / Boot 3.2) was designed as the synchronous successor, so this migration is mostly mechanical — if you know the method-by-method mapping and the three places where behaviour quietly differs. This guide gives you both.
I have now taken three codebases through the Hibernate 5 → 6 → 7 path, and the same pattern repeated each time: the compile errors are the easy part, and the silent behaviour changes — query result types, ID generation, fetch semantics — are what reach production. This guide walks the migration in two deliberate hops (5→6, then 6→7), with the exact errors you will see at each stage and how to fix them. Do not attempt 5→7 in one jump; the diagnostics assume you pass through 6.
A complete migration guide covering every scenario: java.util.Date, Calendar, java.sql types, SimpleDateFormat, Jackson serialisation, Hibernate/JPA mapping, Spring MVC binding, and five migration pitfalls — with before/after code examples for Java 8 through Java 21.
20 copy-paste AI prompts for Java concurrency and CompletableFuture — from basics to advanced production patterns and debugging. Covers thread pools, ExecutorService, CompletableFuture chaining, fan-out/fan-in, timeout handling, virtual threads, deadlock diagnosis, thread dump analysis, and full concurrency audits.
A hands-on comparison of serverless Java AI inference on AWS Lambda, Azure Functions, and Google Cloud Run — with real benchmark data, cost tables, a clear winner recommendation, and code you can run.
Project Leyden brings AOT compilation and persistent caching to standard JVM Java — no native binary required. Learn how it works internally, where it wins, where it fails, and how to use it correctly in production.
A definitive side-by-side comparison of Jackson 3 and Jackson 2 covering the package namespace rename, JacksonException unchecked change, API changes, performance tuning, custom serializer renames, Spring Boot 4 integration, and new features — with annotated code examples for both versions.
A complete, step-by-step guide to migrating from Jackson 2.x to Jackson 3.1.2 — covering the tools.jackson group ID and package rename, the unchecked JacksonException change, removed APIs, ObjectMapper to JsonMapper builder migration, custom serialiser renames, and Spring Boot 3/4 coexistence.