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Ankur in Java

Spring Security 5 to 6 to 7 Migration: SecurityFilterChain, Lambda DSL, and the Silent Authorization Changes

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.

1 min read
Ankur in Java

RestTemplate to RestClient Migration Guide: Method Mapping, Error Handling, and the exchange() Trap

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.

1 min read
Ankur in Hibernate

Hibernate 5 to 6 to 7 Migration Guide: The Breaking Changes and the Silent Ones

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.

1 min read
Ankur in Spring

Zuul to Spring Cloud Gateway Migration: Routes, Filters, and the Blocking-Call Traps

The first time I ported a Zuul gateway to Spring Cloud Gateway, the routes took an afternoon — and the filters took two weeks. That ratio surprises every team that attempts this migration, because the route configuration looks superficially similar while the filter model is a different universe: Zuul 1 is a blocking servlet filter chain, Spring Cloud Gateway runs on Netty with Project Reactor, and a single hidden blocking call in a ported filter can stall your entire gateway. This guide covers the route conversion, the filter-by-filter port, and the blocking-call traps, in that order.

1 min read
Ankur in Spring

Spring Cloud Netflix to Modern Alternatives: The Complete Migration Guide (2026)

In 2020 I published a dozen tutorials on this site covering Eureka, Hystrix, Zuul, Ribbon, and Feign — the Spring Cloud Netflix stack. They were accurate then. Today, most of that stack is dead: Netflix put Hystrix into maintenance mode back in 2018, Zuul 1 and Ribbon followed, and the Spring team removed them from the Spring Cloud release train entirely. If you are still running any of these libraries on Spring Boot 2.x, this guide maps every Netflix component to its modern replacement and shows you the actual migration steps — including the parts that break.

1 min read
Ankur in JUnit

JUnit 6

Complete guide to JUnit 6 with links to all articles covering getting started, core patterns, advanced techniques, mocking, extensions, integration testing, and best practices.

5 min read
Ankur in Java

20 AI Prompts for Java Concurrency and CompletableFuture

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.

2 min read