Mockito for Full Stack Development with Spring Boot

🚀 Built a Mini Online Code Judge github: https://lnkd.in/dctjcFBC I recently developed a lightweight Mini Judge using Java Spring Boot and Vanilla JavaScript — inspired by platforms like Codeforces & HackerRank. 💡 What it does: • Write and run Java code directly in the browser • Provide custom input before execution • Get real-time output instantly • Navigate across multiple coding questions ⚙️ Tech Stack: Frontend — HTML, CSS, JavaScript Backend — Java, Spring Boot Execution — ProcessBuilder (javac & java) Testing — Postman 🔍 Key Features: • Real-time compilation & execution • Compilation + runtime error handling • Input/Output based testing • Multi-question navigation • 5-second timeout to prevent infinite loops 🛠️ How it works: The frontend sends user code + input to the backend via REST APIs → backend compiles & runs the code → output is returned and displayed instantly. This project helped me understand how online judges work internally and improved my backend + system-level thinking. 👨💻 Author: Shailesh Sadanand Sonawane #Java #SpringBoot #WebDevelopment #Coding #Projects #SoftwareDevelopment #LearningByBuild

🚀 From Backend to Frontend with Unit Testing Those who follow my journey know I come from the Java/Spring Boot ecosystem, where unit testing with JUnit and Mockito is a fundamental part of my backend daily routine. I previously applied validations to JSP interfaces, and I'm now extending this culture of quality to the React ecosystem. The transition between languages and frameworks becomes much smoother when we uphold the same software engineering principles: clean, decoupled, and, above all, tested code. What to test in the Front-end? ✅ Isolated Components: Ensuring correct rendering, UI interactions, and accessibility. ✅ Custom Hooks: Validating state logic independently from the UI. ✅ Pure Functions: Testing data manipulation and business rules. #SoftwareEngineering #ReactJS #Testing #Vitest #Java #SpringBoot #CleanCode #FullStack #WebDevelopment

🚀 𝟭𝟬 𝗦𝗽𝗿𝗶𝗻𝗴 𝗔𝗻𝗻𝗼𝘁𝗮𝘁𝗶𝗼𝗻𝘀 𝗘𝘃𝗲𝗿𝘆 𝗝𝗮𝘃𝗮 𝗗𝗲𝘃𝗲𝗹𝗼𝗽𝗲𝗿 𝗦𝗵𝗼𝘂𝗹𝗱 𝗠𝗮𝘀𝘁𝗲𝗿 𝗠𝗼𝘀𝘁 𝗱𝗲𝘃𝗲𝗹𝗼𝗽𝗲𝗿𝘀 𝘀𝘁𝗼𝗽 𝗮𝘁: ✔ @RestController ✔ @Service ✔ @Autowired But Spring becomes truly powerful when you move beyond the basics. Some annotations that make a real difference in production apps 👇 𝗖𝗼𝗻𝗳𝗶𝗴𝘂𝗿𝗮𝘁𝗶𝗼𝗻 & 𝗕𝗲𝗮𝗻 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 @Configuration, @Bean, and @ConfigurationProperties help keep configuration clean, type-safe, and scalable. 𝗔𝗣𝗜 & 𝗩𝗮𝗹𝗶𝗱𝗮𝘁𝗶𝗼𝗻 @ControllerAdvice, @Valid, and @RequestParam reduce boilerplate and make APIs easier to maintain. 𝗣𝗲𝗿𝗳𝗼𝗿𝗺𝗮𝗻𝗰𝗲 & 𝗦𝗮𝗳𝗲𝘁𝘆 @Async, @Transactional, and @Cacheable improve responsiveness, consistency, and speed. 𝗔𝗱𝘃𝗮𝗻𝗰𝗲𝗱 𝗗𝗲𝘀𝗶𝗴𝗻 @EventListener helps build decoupled workflows, while @Profile makes environment-based behavior clean and safe. The real power of Spring annotations is not convenience. It’s how they make design decisions explicit in your code. 𝗢𝗻𝗰𝗲 𝘆𝗼𝘂 𝘀𝘁𝗮𝗿𝘁 𝘂𝘀𝗶𝗻𝗴 𝘁𝗵𝗲 𝗿𝗶𝗴𝗵𝘁 𝗮𝗻𝗻𝗼𝘁𝗮𝘁𝗶𝗼𝗻𝘀, 𝘆𝗼𝘂𝗿 𝗮𝗽𝗽𝗹𝗶𝗰𝗮𝘁𝗶𝗼𝗻 𝗯𝗲𝗰𝗼𝗺𝗲𝘀: ✔ cleaner ✔ safer ✔ easier to scale Which Spring annotation changed the way you build Java applications? #SpringBoot #Java #SpringFramework #JavaDeveloper #BackendDevelopment

🟢 Spring Boot: Spring Boot testēšana — Unit tests ar Mockito 🧪 Writing Better Spring Boot Code Starts With Testing — Here's How I Use Mockito for Unit Tests Unit testing is one of the most powerful skills a Spring Boot developer can have. Yet many teams skip it or write tests that don't actually catch real bugs. After years of working with Spring Boot projects, I've found that proper unit testing with Mockito dramatically improves code quality and developer confidence. The core idea is simple: isolate the class under test by replacing its dependencies with mock objects. Mockito makes this effortless. Key principles I follow: → Use @Mock instead of @MockBean when possible (faster, no Spring context) → Always verify interactions, not just return values → Test edge cases: empty results, exceptions, null inputs → Keep tests focused — one behavior per test method The real value of unit tests isn't just catching bugs today — it's enabling safe refactoring tomorrow. When your test suite is green, you can confidently change implementation details without fear. See the attached diagram for a visual overview of the Mockito unit testing flow in Spring Boot. What's your testing strategy? Do you aim for 80%+ coverage, or focus on critical paths only? Drop your thoughts below! 👇 #SpringBoot #Java #UnitTesting #Mockito #SoftwareTesting #CleanCode #BackendDevelopment #JavaDeveloper #TDD #SoftwareEngineering

Excited to share a major milestone in my backend development journey. Over the past few days, I have been learning and practically implementing core concepts of the Spring Framework through hands-on projects. Instead of only reading theory, I focused on understanding how each concept works internally and how it is used in real-world application development. Concepts I Covered and Implemented: • Spring Core XML Configuration Learned how to configure beans using XML files, define dependencies, and let the Spring container manage object creation. • Collection Type Dependency Injection Understood how to inject collections such as List, Set, Map, and Properties into Spring beans. • Java-Based Configuration Explored modern configuration using @Configuration and @Bean annotations instead of XML. • Annotation-Based Configuration Worked with annotations to simplify configuration and reduce boilerplate code. • Component Scanning Learned how Spring automatically detects classes using stereotypes like @Component, @Service, @Repository, and registers them as beans. • Dependency Injection with @Autowired Implemented automatic dependency injection and understood how Spring resolves dependencies. • Constructor Injection & Setter Injection Practiced both approaches and learned when each should be used for cleaner and more maintainable design. • Bean Lifecycle & Object Management Learned how Spring manages bean creation, initialization, dependency resolution, and destruction. • Layered Project Structure Organized projects using config, repository, service, and test packages to follow professional development practices. Key Learnings: • Spring promotes loose coupling and better code maintainability. • It reduces manual object creation and improves scalability. • Clean architecture becomes easier when responsibilities are separated properly. • Practical implementation gives much deeper understanding than theory alone. This journey helped me strengthen my Java fundamentals while taking my first serious step into backend development. A sincere thanks to Prasoon Bidua Sir for the guidance and support throughout the learning process. Now moving forward to the next phase: Spring Boot, REST APIs, and real-world backend projects. #Java #Spring #SpringFramework #SpringBoot #BackendDevelopment #DependencyInjection #IoC #SoftwareDevelopment #Programming #CodingJourney #LearningInPublic

Clean code in backend development is not about making code look “smart.” It’s about making it easy to understand, maintain and debug. A few practices that improve code quality in Java backend applications: - use meaningful class and method names - keep methods focused on a single responsibility - avoid hardcoded values and magic numbers - write reusable and modular business logic - handle exceptions consistently - keep controllers thin and move logic to services - remove unused code instead of leaving commented blocks In production systems, readable code saves time during debugging, onboarding and incident handling. Code is written once but read many times. #Java #BackendDevelopment #CleanCode #SpringBoot #SoftwareEngineering

6 rules that'll help you write clean code: 1 Separation of Concerns (SOC) ↳ Break down a complex program into smaller units. ↳ Each unit should focus on a specific task. 2 Document Your Code (DYC) ↳ Write code for your future self and others. ↳ Explain complex code sections with comments & documentation. 3 Don't Repeat Yourself (DRY) ↳ Don't waste time writing the same code again. ↳ Instead use functions, modules & existing libraries. 4 Keep It Simple, Stupid (KISS) ↳ Simple is hard, but better. ↳ Readable code > clever code. 5 Test Driven Development (TDD) ↳ Write a failing test first. ↳ Write code to make the test pass. ↳ Then clean up the code without changing behaviour. 6 You Ain't Gonna Need It (YAGNI) ↳ Build only essential features. ↳ Don't build features you think you might need later. === Bottom line: Leave the codebase cleaner than you found it. Credits : Neo Kim #software #mern #nodejs #java #javascript #springboot #css3 #html5

I’ve been structuring my Java projects using the classic package-based approach for a long time… until TODAY. I tried a feature-based structure — and honestly, it just clicked. Instead of spreading logic across controllers, services, repositories, and DTO packages, everything related to a single feature lives in one place. The difference is huge: • Easier to navigate — no more jumping across multiple packages • Better scalability — doesn’t turn into chaos as the project grows • Closer to real business domains (user, order, payment) • Refactoring becomes much simpler (even moving to microservices later) • Cleaner collaboration — fewer Git conflicts in teams It feels less like “organizing code by type” and more like “organizing by purpose”. For anyone building serious backend systems (especially with Spring Boot), I’d definitely recommend trying feature-based structure at least once. Curious — are you still using package-based, or have you switched already? #java #springBoot #spring #code

🚀 Maven — Simplified in One View! If you’re working with Java or Spring Boot, Maven is your backbone for building scalable applications. This single visual covers everything you need to know: 🔹 Project Structure 🔹 pom.xml (Core of Maven) 🔹 Dependency Management 🔹 Build Lifecycle (Clean → Deploy) 🔹 Plugins & Goals 🔹 Essential Maven Commands 💡 Maven takes care of dependencies, builds, and project structure — so you can focus on writing better code. Whether you're preparing for interviews or building real-world projects, mastering Maven is a must. 👉 Save this for quick revision 👉 Share with your developer friends #Java #SpringBoot #Maven #BackendDevelopment #SoftwareEngineering #Developers #Coding

Architecture vs. Speed: When is 8 classes for one task actually worth it? 🚀 As a Senior Developer, I often see a common struggle: when to keep it simple and when to build a robust architecture. In my latest video for Let’s Code Java, I took a simple console app and transformed it into a professional, service-oriented system. The result? I added 8 new classes (builders, services, exception hierarchy), but technically... I didn’t add a single new feature. Was it worth it? It depends. If you're building a prototype, this level of engineering will only slow you down. But if you’re working on a long-term enterprise project, skipping this foundation will cost you twice as much time later when you have to refactor "dirty" code. In this episode, I dive deep into: ✅ Building a Custom Exception Hierarchy that doesn't mess up your logic. ✅ Implementing a Service Layer to isolate business rules from I/O. ✅ Using the Builder Pattern to ensure object validity from the start. ✅ Preparing the ground for Spring Boot & REST API. If you want to see how to design Java applications that are ready for the real world (and why "perfect" code isn't always the goal), check out the video in the first comment. Question for my fellow devs: Where do you draw the line between "clean architecture" and "over-engineering"? Let’s discuss in the comments! 👇 #Java #SoftwareArchitecture #CleanCode #BackendDevelopment #JavaDeveloper #ProgrammingTips #SpringBoot #LetsCodeJava