I'm a Java and Spring Boot Engineer and Open Source Contributor focused on backend engineering, microservices, enterprise Java, cloud-native systems, and modern full-stack development.

My primary backend stack is Java and Spring Boot, with hands-on experience in REST APIs, microservices, databases, security, testing, Docker, Kubernetes, AWS, Terraform, and AI-powered applications.

I contribute to open-source projects in the Java ecosystem, including Eclipse JNoSQL, Jakarta EE, Jakarta Data, Jakarta Agentic AI, and Spring-related projects, where I investigate real issues, build reproducible test cases, implement fixes, contribute regression and TCK tests, and improve maintainability.

• Java & Spring Boot
• Spring Framework & Spring Security
• Microservices & REST APIs
• Jakarta EE & Jakarta Data
• Jakarta Persistence & Jakarta NoSQL
• Eclipse JNoSQL
• Jakarta Agentic AI
• PostgreSQL & MySQL
• Docker & Kubernetes
• AWS & Terraform
• Angular, React & Next.js
• Spring AI & AI-powered applications
• Data structures & algorithms

GitHub: mhnuk2007 Primary focus: Java • Spring Boot • Microservices • Jakarta EE • Cloud • Open Source

Contributing to Jakarta Data through TCK development, asynchronous behavior testing, transaction semantics, and compatibility-oriented test coverage.

Jakarta Data — PR #1556 · Merged

Added TCK coverage verifying that an asynchronous repository operation completes exceptionally when an insert violates an existing entity constraint.

What I contributed:

• Tested exceptional CompletionStage completion.
• Verified EntityExistsException as the underlying cause.
• Added regression coverage for asynchronous repository behavior.
• Validated the test against Open Liberty.
• Incorporated review feedback and finalized the portable TCK scenario.

Validation:

mvn clean verify — successful
Open Liberty execution — successful

🔗 Issue #19 · Merged PR #1556

Jakarta Data — PR #1561 · Merged

Added TCK coverage for:

@QueryOptions(flush = QueryFlushMode.FLUSH)

on a repository method using @JakartaQuery.

The test verifies that a pending entity modification becomes visible to the repository operation within an active transaction without an explicit flush.

What I contributed:

• Added a @JakartaQuery repository scenario.
• Added QueryOptions / QueryFlushMode.FLUSH coverage.
• Designed the test around portable Jakarta Data transaction semantics.
• Revised the test based on TCK review feedback.
• Verified the scenario against a development Open Liberty environment.

🔗 Merged PR #1561

Jakarta Data — PR #1567 · Open

Added the remaining @QueryOptions scenarios from Jakarta Data issue #965:

• @Find
• @Query
• @Delete
• @NativeQuery

Each test verifies that a pending entity modification becomes visible to the repository operation when using:

@QueryOptions(flush = QueryFlushMode.FLUSH)

What I contributed:

• Added @Find + QueryOptions coverage.
• Added @Query + QueryOptions coverage.
• Added @Delete + QueryOptions coverage.
• Added @NativeQuery + QueryOptions coverage.
• Designed the scenarios around active transaction semantics.
• Kept the tests portable and independent of a particular EntityManager.
• Validated compilation and formatting.
• All PR checks are currently passing.

Status: Open — awaiting review.

🔗 Issue #965 · PR #1567

Contributing to the Jakarta NoSQL ecosystem through bug investigation, root-cause analysis, reproducible testing, regression coverage, production fixes, reusable utilities, and maintainability improvements.

JNoSQL Extensions — PR #209 · Merged

Identified and fixed an issue where Page.totalElements() could fail after an automatically created repository transaction had completed.

What I contributed:

• Traced the transaction lifecycle around repository method execution.
• Identified that Page content was eagerly loaded while totals remained lazy.
• Updated EnsureTransactionInterceptor to evaluate totalElements() while the automatically created transaction was still active.
• Added PageOutsideTransactionTest as a regression test.
• Contributed the fix to the 1.1.x branch.

Result: Page.totalElements() can safely be accessed after the repository call returns.

🔗 Issue #707 · Merged PR #209

JNoSQL Extensions — PR #210 · Merged

After a major Jakarta Persistence refactoring, I ported the regression scenario from the 1.1.x fix to the main branch.

What I contributed:

• Adapted the regression test to the new implementation.
• Verified that Page.totalElements() remains accessible without an active transaction.
• Reused the repository-level scenario against the refactored implementation.
• Added permanent regression coverage to main.

🔗 Merged PR #210

JNoSQL — Issue #631 / PR #765 · Merged

Investigated a NoSQLException reported in a reactive Quarkus application where ConstructorBuilderSupplier could not be discovered during initialization.

The issue was traced to Java ServiceLoader provider discovery and thread context class loader (TCCL) visibility.

What I contributed:

• Investigated the failure using standalone and Quarkus/Vert.x reproducer projects.
• Isolated the problem to ServiceLoader provider discovery and class-loader visibility.
• Implemented a TCCL-first with defining-class-loader fallback strategy.
• Preserved normal TCCL-based provider discovery where available.
• Added regression coverage using an isolated TCCL.
• Validated the fix with dedicated regression tests and downstream reproducer scenarios.

Result: ConstructorBuilderSupplier can still be discovered when the current thread's context class loader cannot see the provider.

🔗 Issue #631 · Merged PR #765

JNoSQL — PR #768 · Merged

Applied the same ConstructorBuilder ServiceLoader fix to the main branch targeting the Jakarta EE 12 line.

What I contributed:

• Added the TCCL-first provider lookup strategy.
• Added fallback to ConstructorBuilder.class.getClassLoader().
• Added a dedicated regression test using an isolated TCCL.
• Verified provider discovery through the fallback path.
• Ran the complete jnosql-mapping-api-core test suite.

Validation:

Dedicated regression test:
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0

Complete module test suite:
Tests run: 67, Failures: 0, Errors: 0, Skipped: 0

Checkstyle: 0 violations
Apache RAT: 0 unapproved files
Java 21 CI: Passed
Java 25 CI: Passed
Eclipse Contributor Agreement check: Passed

🔗 Merged PR #768

JNoSQL — PR #764 · Merged

Worked on support for asynchronous repository methods returning CompletionStage types.

What I contributed:

• CompletionStage<T>
• CompletionStage<List<T>>
• CompletionStage<Optional<T>>
• CompletionStage<Page<T>>
• Regression coverage for asynchronous repository return types.
• Kept the asynchronous capability change separate from the class-loader fix.

🔗 Merged PR #764

JNoSQL — Issue #766 → PR #769

After investigating repeated class-loader and ServiceLoader handling patterns, I worked on extracting common provider-loading behavior into reusable infrastructure.

What I contributed:

• Investigated repeated ServiceLoader lookup patterns.
• Designed reusable provider-discovery behavior.
• Added tests covering provider loading.
• Migrated affected consumers.
• Preserved class-loader fallback behavior.
• Kept the reusable utility separate from the targeted ConstructorBuilder bug fix.

🔗 Issue #766 · PR #769

JNoSQL — PR #770 · Merged

Contributed a project-wide license-header update to align source files with the project's current licensing requirements.

What I contributed:

• Updated affected source-file license headers.
• Applied the required Eclipse Public License 2.0 / Apache License 2.0 notices.
• Preserved the project's existing licensing structure.
• Validated the changes with compliance checks.

🔗 Merged PR #770

Contributing to the Jakarta Agentic AI project through practical improvements to example applications and domain models.

Jakarta Agentic AI — Issue #11 / PR #59 · Merged

Updated the fraud-detection example's BankTransaction model to represent monetary values using JSR 354 MonetaryAmount, making the example closer to a realistic financial domain model.

What I contributed:

• Replaced the simplistic monetary representation with JSR 354 MonetaryAmount.
• Added the required Money API dependency.
• Updated the transaction domain model.
• Added getters and setters.
• Verified the implementation with Maven tests.

🔗 Issue #11 · Merged PR #59

Spring Lens — Issue #269 / PR #270 · Merged

Implemented an immutable domain model for aggregating Spring bean-definition metrics.

What I contributed:

• Added the immutable BeanDefinitionSummary Java record.
• Implemented defensive copying using Map.copyOf().
• Added null-safe handling for distribution maps.
• Added validation for non-negative bean-definition totals.
• Introduced LoadingMode with EAGER and LAZY values.
• Added comprehensive unit tests.
• Added JavaDoc for the model and factory method.

Testing:

BeanDefinitionSummaryTest:
5 tests passed

🔗 Issue #269 · Merged PR #270

Open source has changed the way I approach software engineering.

It has pushed me beyond simply writing code that works. I have learned to investigate unfamiliar codebases, reproduce difficult failures, trace framework behavior, understand class loaders and transaction lifecycles, work with Java platform APIs, write regression and TCK tests, respond to review feedback, extract reusable utilities, and maintain changes across multiple release branches.

The most valuable lesson has been simple:

Confidence does not always come before difficult work. Sometimes confidence is built by doing the difficult work you initially think you are not ready for.

Every issue investigated, reproducer built, failed hypothesis, regression test, review, reusable utility, and merged pull request has made me a better engineer.

I started contributing to learn from established open-source projects. Along the way, I discovered that I could investigate real problems, understand complex systems, and contribute meaningful fixes.

Open source has not only improved my GitHub profile — it has improved my confidence as an engineer.

My primary development focus is Java and Spring Boot, with continued work in:

• Spring Boot
• Spring Framework
• Spring Security
• REST APIs
• Microservices
• Persistence
• Testing
• Cloud-native applications
• AI integration

Continuing to learn and contribute to the Jakarta ecosystem through hands-on work with:

• Jakarta EE
• Jakarta Data
• Jakarta Persistence
• Jakarta NoSQL
• Eclipse JNoSQL
• TCK development
• ServiceLoader and class-loader behavior
• Transaction management
• Repository abstractions
• Asynchronous repository APIs
• CompletionStage

Exploring practical AI application development through:

• Jakarta Agentic AI
• Spring AI
• Agentic AI applications
• Java-based AI systems
• Enterprise AI architecture
• Vector search
• Embeddings
• Retrieval-Augmented Generation

Practicing algorithmic problem solving with Java:

• Time complexity
• Space complexity
• Pattern recognition
• Dynamic programming
• Sliding window
• Two pointers
• Binary search
• Hashing
• Trees and graphs

LeetCode: @mhnuk2007 Java DSA: leetcodepractice

• Big-O analysis
• Recursion
• Algorithm optimization
• Memoization
• Dynamic programming

Exploring C# and .NET fundamentals through hands-on console applications covering:

• C# fundamentals
• OOP
• Collections
• Exception handling
• Parsing and type conversion

Java • Spring Boot • Spring Framework • Spring Security • Spring AI • Microservices • REST APIs

• RESTful API design
• Microservices architecture
• Authentication and authorization
• OAuth2 and JWT
• Database integration
• Testing and regression coverage
• AI-powered backend applications

Jakarta EE • Jakarta Data • Jakarta Persistence • Jakarta NoSQL • Eclipse JNoSQL • ServiceLoader

• Enterprise Java APIs
• Persistence
• TCK development
• Repository abstractions
• Transaction management
• Service provider discovery
• Class-loader behavior
• Asynchronous repository APIs
• CompletionStage-based repository methods

Angular • React • Next.js • TypeScript • JavaScript

• Component architecture
• State management
• Responsive interfaces
• Type-safe development
• Performance optimization

AWS • Docker • Kubernetes • Terraform • CI/CD

• Containerization
• Kubernetes orchestration
• Infrastructure as Code
• Cloud deployments
• Automated testing and deployment

PostgreSQL • MySQL • pgvector • Spring AI

• Relational database design
• Query optimization
• Vector search
• Embeddings
• Semantic search
• Retrieval-Augmented Generation patterns

• ✅ Problem Solver — I investigate, reproduce, debug, and fix difficult problems.
• ☕ Java & Spring Boot Focused — My primary backend ecosystem.
• 🌐 Open Source Contributor — Experience working with real Java ecosystem codebases.
• 🧩 Jakarta Ecosystem Contributor — Hands-on contribution to Jakarta Data, Jakarta EE, Jakarta NoSQL, and Jakarta Agentic AI.
• 🧪 Testing Mindset — Experience with regression tests, TCK scenarios, compatibility testing, and CI validation.
• 🏗️ Production Mindset — Focused on testing, maintainability, reliability, and scalability.
• 📚 Self-Directed Learner — I continuously learn by building, investigating, and contributing.
• 🚀 Continuous Improvement — Every issue and code review is an opportunity to become a better engineer.