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Ankur in Java

Image Generation and Vision in Spring AI: ImageModel, Prompt Options and Safe Storage

How to generate images with Spring AI's ImageModel and keep them safely: what the real OpenAiImageModel sends (including an options object that silently resets the model), a moderation gate and what Spring AI does not moderate, verified storage in MinIO/S3 with sniffed content types, size and pixel caps and server-chosen keys, and a per-provider cost table dated 2026-10-28. No image provider was called; the model and moderation are scripted fakes and the bucket is a real MinIO.

Ankur in Java

Rate Limiting Spring Boot APIs with Bucket4j and Redis: Per-User, Per-Key and Global Limits

Build rate limiting into a Spring Boot 4.1 API with Bucket4j 8.21 and Redis: per-user, per-API-key and global token buckets in a servlet filter, 429 with Retry-After and X-RateLimit headers, two instances sharing one bucket, and the failures worth reproducing (limit changes that do nothing, clock skew, Redis down), all with tests that assert it.

Ankur in Hibernate

Soft Delete in Hibernate 7: @SoftDelete vs @SQLDelete + @SQLRestriction

Hibernate 7's native @SoftDelete (DELETED, ACTIVE and TIMESTAMP strategies) compared with the hand-rolled @SQLDelete + @SQLRestriction recipe, run against PostgreSQL 17 and H2: the generated SQL, restoring rows, the unique-index traps (partial indexes, NULLS NOT DISTINCT), associations and join tables, native queries that bypass the filter, and what Spring Data JPA does with it.

Ankur in Java

Spring Boot 4 + Thymeleaf + htmx: Server-Side CRUD UI in 2026

Build a contacts screen with Spring Boot 4.1.2, Thymeleaf 3.1.5 and htmx 2.0.11 and no JS framework: one URL that returns a full page or a fragment, 422 validation re-render, pagination, inline edit and delete, with MockMvc tests and a headless Chromium check, and the htmx 2 status-code traps that bit during the build.

Ankur in Java

Java Multithreading Programs for Interviews: Odd-Even Printing, Ping-Pong, Ordered Threads, Deadlock

The four classic multithreading programs in Java, solved with wait/notify, Semaphore, ReentrantLock + Condition and virtual threads: odd-even printing, ping-pong, ordered threads and a deadlock detected with ThreadMXBean and fixed by lock ordering and tryLock. Every program is runnable with asserted output.

Ankur in Java

Key Derivation Function API in Java (JEP 510): HKDF Explained with Real Examples

JEP 510 made javax.crypto.KDF final in JDK 25. A beginner-first guide to HKDF extract and expand, per-tenant key derivation with info context separation, RFC 5869 vectors, interop checks against Python cryptography and openssl, and the mistakes that silently break it.

Ankur in Java

GraphRAG in Java with Neo4j and Spring AI: Turning Documents into a Knowledge Graph

Build GraphRAG in Java: extract entities and relations with Spring AI structured output, store them in Neo4j with a vector index, answer multi-hop questions with Cypher, and measure it against plain vector RAG on the same 35 documents. The extraction step is a rule-based stand-in, not an LLM, and the post says so.

Ankur in Java

Speech-to-Text and Text-to-Speech with Spring AI: Build a Meeting-Minutes Generator

Spring AI's audio API is its least-covered corner. Build a meeting-minutes generator on Spring AI 2.0.2: transcribe a recording, split files over the 25 MB upload limit at a silence, turn the transcript into typed action items with entity(), read them back with text-to-speech, and price an hour of meetings. Run against a local mock server and a stub chat model, with the failures captured.

Ankur in Java

Top 30 JUnit 6 and Mockito Interview Questions (2026)

30 JUnit 6 and Mockito 5 interview questions answered with tests that were actually run on JUnit 6.1.3, Mockito 5.24.0 and JDK 25: lifecycle, extensions, parameterized tests, mocks vs spies, verify, static mocking and flaky tests, each with captured output.