Hire the Best J2EE Developers

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Rafael M.

Rio de Janeiro, Brazil

$85/hr
5.0
13 jobs

I build mobile apps — the real kind, native, shipped to the store, used by actual people — and lately the AI systems inside them. I've been doing the first for 20 years and the second long enough to know where it actually pays off. I'm Expert-Vetted on Upwork (top 1% of talent), with 100% Job Success, 5,700+ hours, and $200K+ earned. Behind that is 20+ years in software — a decade architecting enterprise systems at Accenture for Fortune 500s, then CTO of a SaaS startup I scaled from 3 to 30+ engineers and took to consumer scale. I'm completing Stanford's AI Professional Program now. What you get is a CTO-caliber technologist who never stopped writing production code. I work two ways, depending on what you need: ⸻ ★ MOBILE APPS — zero to App Store ★ (fixed-price) You have an idea or a validated concept; I deliver the finished app, live in the App Store and Play Store. Architecture, design, frontend, backend, deployment, and the part most people underestimate — actually getting through store review, native builds, push, Live Activities, the works. I've shipped 20+ mobile apps, several used by hundreds of thousands of people, and I handle the whole build personally. Shipping a native app to a store is a different discipline than deploying a web app, and it's the discipline I've spent years in. ★ AI SYSTEMS — design & build ★ (hourly) Production AI/LLM systems, not prototypes. My recent work is a multi-vendor LLM pipeline that benchmarked 21 model-and-strategy combinations across Claude, GPT, and Gemini over 54 recipe sources in 7 countries — automated quality scoring against an Opus gold-standard reference, and cost tuned across a 150x price spread down to the best quality-per-dollar. The hard part of AI work isn't calling an API; it's knowing where AI actually earns its keep, which model fits which job, and how to architect a pipeline that holds up in production. That's what I do, then I build it — often straight into the mobile products above. ⸻ The background behind that: 10 years at Accenture on large-scale systems for Fortune 500s in healthcare, telecom, oil & gas, and retail. Then CTO at a SaaS startup — engineering scaled 3 to 40, a multi-service platform shipped with payments, identity, and real-time processing running at consumer scale. 📎 Stanford — AI Professional Program (completing August 2026) 📎 Kellogg — Product Strategy 📎 TOGAF Certified Enterprise Architect ⸻ Native Mobile (React Native / Expo, App Store & Play Store delivery) · TypeScript/JavaScript · LLM APIs (Claude, GPT, Gemini) · Prompt Engineering · Multi-Model Pipelines · React · Next.js · Node.js · Supabase · PostgreSQL · AWS · Solution Architecture

Raja Dushyant V.

Jaipur, India

$50/hr
4.4
63 jobs

Greetings All, I'm a Lead Architect with 11+ years of experience in web development. I have developed different kinds of projects, including eCommerce systems, CRM software, corporate websites, APIs and other internal scripts. • A quick learner with a penchant of performing under pressure. strong team player with excellent interpersonal and communication skills, strong analytical and problem solving skills. • Overall 11+ years of experience in development of Mobile, Web & Enterprise applications using PHP5, JAVA and J2EE Technologies. • Artificial Intelligence and Automation - Prompt Engineering, AI Agent Development using n8n - Large Language Model Integration and Conversational AI using Langchain and Botpress - AI Chatbots, Retail AI Voice Bots, and Generative AI • Hands on experience in Core Java, Servlets, JSP, JDBC, Spring, SpringBoot, Hibernate, JPA, JavaFX, JacpFX. • Hands on experience with DevOps, Shell Script, Docker, Docker Compose, Jenkins, AKS, Azure • Hands on experience in NodeJS, Angular, Angular 2-rc3, Ionic Framework. • Hands on experience in ReactJs and Redux Frameworks. • Hands on experience in MySQL, Postgres, Oracle, MongoDB, ArangoDB, SQL Server. • Hands on experience in Apache, Weblogic, Glassfish, JBoss/Wildfly and Tomcat web servers. • Hands on experience in Ejabberd, Openfire and Prosody XMPP Chat servers. • Hands on experience in WebRTC. • Knowledge of Eclipse, Intellij Idea, WebStorm tool for the development of java projects & Node/Angular. • Knowledge of Adobe DW, Aptana studio tool, PHPStorm for the development of PHP projects. • Knowledge of Business Process Management Tool jBPM5.3. Let me know about your goals and I will lead your project to success! ;)

  • J2EE
  • JavaScript
  • Spring Boot
  • PostgreSQL
  • Spring Framework
  • Apache Struts
  • jQuery
  • Spring Security
  • Hibernate
  • Java
  • Kotlin
  • Spring MVC
Terence B.

Lapu-Lapu, Philippines

$45/hr
5.0
28 jobs

🏆 𝗨𝗣𝗪𝗢𝗥𝗞 𝗘𝗫𝗣𝗘𝗥𝗧 𝗩𝗘𝗧𝗧𝗘𝗗 💪 Top 1% of performers | 15,000+ hours 🎖️ Top Rated Plus | 100% Job Success ✔︎ 20+ years experience in Embedded Systems, IoT & Full Stack Development I design and develop production-grade embedded and IoT systems, from firmware and hardware integration to cloud-connected platforms. Specialized in STM32, Nordic nRF52/nRF53/nRF91, ESP32, RTOS (FreeRTOS/Zephyr), and secure C/C++ firmware development. I help companies turn hardware concepts into reliable, scalable, real-world products. 🚀 𝗔𝗕𝗢𝗨𝗧 𝗠𝗘 I am a Senior Embedded Systems and IoT Engineer with over 20 years of experience delivering production-ready systems across embedded firmware, hardware design, cloud infrastructure, and full stack applications. I specialize in end-to-end system development — from low-level firmware and PCB collaboration to cloud integration and application layers — ensuring robust and scalable real-world deployments. I work with startups and engineering teams to transform complex ideas into reliable production systems. 🔧 𝗘𝗠𝗕𝗘𝗗𝗗𝗘𝗗 𝗦𝗬𝗦𝗧𝗘𝗠𝗦 & 𝗙𝗜𝗥𝗠𝗪𝗔𝗥𝗘 Extensive experience in production-grade embedded firmware development. ▸ 𝗠𝗜𝗖𝗥𝗢𝗖𝗢𝗡𝗧𝗥𝗢𝗟𝗟𝗘𝗥𝗦 & 𝗣𝗟𝗔𝗧𝗙𝗢𝗥𝗠𝗦 ▪ ARM Cortex-M ▪ STM32 ▪ Nordic nRF52 / nRF53 / nRF91 ▪ ESP32 / ESP8266 ▪ Raspberry Pi ▪ Arduino ▪ Microchip PIC ▪ Silicon Labs BGM220 ▸ 𝗥𝗧𝗢𝗦 & 𝗘𝗠𝗕𝗘𝗗𝗗𝗘𝗗 𝗔𝗥𝗖𝗛𝗜𝗧𝗘𝗖𝗧𝗨𝗥𝗘𝗦 ▪ FreeRTOS ▪ Zephyr RTOS ▪ Bare-metal firmware ▪ Multi-threaded systems ▪ Event-driven architectures ▪ OTA firmware updates ▪ Secure boot & encrypted firmware ▸ 𝗖𝗢𝗠𝗠𝗨𝗡𝗜𝗖𝗔𝗧𝗜𝗢𝗡 & 𝗪𝗜𝗥𝗘𝗟𝗘𝗦𝗦 ▪ UART, SPI, I2C, USB ▪ BLE, Bluetooth Classic ▪ LoRa / LoRaWAN ▪ Wi-Fi, LTE, NB-IoT ▪ RS232 / RS485 ▸ 𝗦𝗘𝗖𝗨𝗥𝗜𝗧𝗬 & 𝗡𝗘𝗧𝗪𝗢𝗥𝗞𝗜𝗡𝗚 ▪ TCP/IP, MQTT, HTTP/HTTPS ▪ TLS / mbedTLS ▪ ARM TrustZone ▪ Secure elements (Optiga, ST-SAFE) ▪ PKI systems ▪ JSON, XML, Protobuf ☁️ 𝗜𝗢𝗧 & 𝗖𝗟𝗢𝗨𝗗 𝗦𝗬𝗦𝗧𝗘𝗠𝗦 ▪ AWS IoT, EC2, S3, RDS ▪ MQTT-based architectures ▪ Industrial IoT platforms ▪ Telemetry & remote monitoring ▪ Cellular / NB-IoT / LTE devices ▪ Robotics & automation systems 💻 𝗙𝗨𝗟𝗟 𝗦𝗧𝗔𝗖𝗞 𝗗𝗘𝗩𝗘𝗟𝗢𝗣𝗠𝗘𝗡𝗧 ▸ 𝗕𝗔𝗖𝗞𝗘𝗡𝗗 ▪ Java (J2SE/J2EE), Spring ▪ JSF, JSP, Servlets ▪ Hibernate, JPA ▪ Node.js ▪ PHP / CakePHP ▪ REST APIs ▸ 𝗙𝗥𝗢𝗡𝗧𝗘𝗡𝗗 ▪ ReactJS ▪ JavaScript, HTML5, CSS3, Bootstrap ▸ 𝗗𝗔𝗧𝗔𝗕𝗔𝗦𝗘𝗦 ▪ MySQL ▪ Apache Derby ▪ Database design & optimization 🛠 𝗛𝗔𝗥𝗗𝗪𝗔𝗥𝗘 & 𝗣𝗖𝗕 𝗗𝗘𝗦𝗜𝗚𝗡 ▪ PCB design (Altium Designer / KiCad) ▪ Analog & digital circuit design ▪ Hardware bring-up & debugging ▪ Sensor integration ▪ Power systems ▪ Motor control (PWM, stepper, servo, robotics) 🧠 𝗜𝗠𝗔𝗚𝗘 𝗣𝗥𝗢𝗖𝗘𝗦𝗦𝗜𝗡𝗚 & 𝗔𝗜 ▪ OCR systems ▪ Signal processing & filtering ▪ Embedded AI / ML integration ▪ Sensor data conditioning ▪ Computer vision pipelines 🧪 𝗤𝗨𝗔𝗟𝗜𝗧𝗬 & 𝗦𝗘𝗖𝗨𝗥𝗜𝗧𝗬 ▪ Secure firmware architecture ▪ Veracode static/dynamic analysis ▪ System debugging & reliability engineering ▪ Performance optimization ▪ Production-grade system hardening 🧾 𝗣𝗥𝗢𝗚𝗥𝗔𝗠𝗠𝗜𝗡𝗚 𝗟𝗔𝗡𝗚𝗨𝗔𝗚𝗘𝗦 ▪ C / C++ ▪ Embedded C ▪ Java ▪ Python ▪ JavaScript ▪ PHP ▪ MATLAB 🎯 𝗗𝗘𝗩𝗘𝗟𝗢𝗣𝗠𝗘𝗡𝗧 𝗣𝗛𝗜𝗟𝗢𝗦𝗢𝗣𝗛𝗬 I focus on building reliable, maintainable, and production-ready systems by combining strong engineering fundamentals with real-world product experience across hardware, firmware, cloud, and software layers. If you need embedded firmware, IoT systems, cloud integration, or full stack development, I can help bring your product from concept to production.

Zakaria B.

Temara, Morocco

$25/hr
5.0
58 jobs

I help startups and SaaS teams ship reliable, well-tested products by combining structured QA practices with a strong technical and SEO background. I’m a QA-focused engineer with hands-on experience testing AI-driven web applications like Noveli, where I designed and executed test cases, validated critical user flows (authentication, validation, content generation), and introduced automated testing using Cypress. I also bring experience with Playwright and CI/CD workflows to ensure consistent quality across releases. 🔹 What I Do Best QA & Testing (Primary Focus) Manual testing (functional, regression, exploratory) Test case design & documentation Clear, actionable bug reporting End-to-end testing with Cypress & Playwright CI/CD testing integration Technical & SEO Support (Secondary Strength) Technical SEO (indexing, site structure, performance) Debugging SEO-impacting issues (rendering, metadata, crawlability) Programmatic SEO systems (Next.js + CMS) Development Background (Supporting Skill) Frontend & backend debugging (React, Next.js, Node.js) Understanding of application architecture → better test coverage API testing & workflow automation (Zapier, Make) 🔹 Why Clients Work With Me I don’t just test—I understand how the product is built, which leads to deeper, more effective QA Experience with AI products and complex user flows (chatbots, dynamic content, edge cases) Strong focus on clarity, documentation, and reproducibility Able to move fast while maintaining structured QA processes Multilingual: English, French, Arabic If you need someone who can quickly understand your product, identify critical issues, and improve overall quality, I’m ready to jump in and contribute immediately.

Khoi V.

Hanoi, Vietnam

$15/hr
5.0
1 jobs

Engineer 7+ years with AI mind set delivering growing and long-term products for clients across the US, Israel, Japan... across domains like eCommerce, Fintech systems, adTech platforms, and enterprise web integrations. • Enterprise Systems: Role-based, Tenant-based systerm, Authentication follow, Design system,.. • eCommerce: Product catalogs, checkout + order flows, inventory sync,... • AdTech: Campaign builders, analytics dashboards, API integrations,... • Web Integration: Payment integration, Twilio, Firebase, Google APIs, legacy system migration,.. BACKEND: Java 11–25 · Spring Boot 2 & 3 & 4 · Kotlin · TypeScript · NestJS · Quarkus · Microservices · REST API · Firebase FRONTEND React.js · Angular · Vue.js · TypeScript · JavaScript · HTMX AI FIRST NATIVE Claude · Codex · windsurf DATABASE & MIGRATIONS PostgreSQL · MySQL · MongoDB · Liquibase · Flyway SECURITY & DEVOPS OAuth2 · Keycloak · SonarQube · Docker · GitHub Actions · CI/CD THIRD-PARTY INTEGRATIONS Stripe · PayPal · Myfatoorah · Twilio · Telnyx · Google APIs · Firebase API · Algolia Search · reCAPTCHA 100% Job Success Long-term client relationships End-to-end ownership from dev → test → deploy. Let's discuss your project.

Harmeet K.

Sangrur, India

$40/hr
4.9
59 jobs

Over the last 10+ years, I’ve architected and scaled SaaS platforms, enterprise systems, and cloud-native applications used by startups and growing businesses across healthcare, fintech, logistics, travel, AI, and real estate industries. I specialize in Java, Spring Boot, Microservices, AWS, PostgreSQL, MongoDB, Kubernetes, and scalable backend architecture for high-performance SaaS platforms. Worked on platforms handling real-time workflows, payment systems, enterprise reporting, AI integrations, booking engines, analytics systems, and multi-tenant SaaS infrastructure. I’ve developed enterprise-grade platforms for healthcare, fintech, e-commerce, and real-time applications, focusing on scalability, security, and long-term maintainability. My expertise includes: ✔ High-performance REST APIs ✔ Microservices architecture ✔ Cloud-native AWS deployments ✔ Authentication & payment systems ✔ Enterprise integrations ✔ Performance optimization Whether you need to modernize a legacy Java application, build a backend from scratch, or scale an existing SaaS platform, I can help architect and deliver reliable production-ready systems. My Core Competencies 1. Java Development: - Core Java: In-depth knowledge of Java’s features, collections, concurrency, and multi-threading - Spring Framework: Expertise in Spring Boot, Spring MVC, Spring Security - Microservices: Designing and implementing microservices architecture with Spring Cloud - API Development: RESTful APIs with JWT, OAuth, and GraphQL integration 2. Mobile App Development: - Android Development: Skilled in developing native Android apps using Java and Kotlin - App Lifecycle: From UI/UX design to API integration and deployment 3. Database & Back-End: - Database Expertise: Proficient in MySQL, PostgreSQL, and MongoDB for secure, scalable data management - ORM: Working with Hibernate for object-relational mapping - Server-Side Scripting: Building efficient backends with Java and Spring. 4. Deployment & Cloud: - Cloud Deployment: Expertise in deploying Java-based applications on AWS, Azure, and Google Cloud - Containerization: Proficient with Docker for application containerization and management 5. Security & Performance: - Application Security: Implementing secure systems with Spring Security, OAuth, and data encryption - Performance Tuning: Optimizing application speed, database queries, and server-side performance Industries I Serve - E-Commerce: Custom checkout systems, payment gateway integration, and scalable shopping carts - Healthcare: HIPAA-compliant mobile apps and backend systems for patient management - Finance: Developing secure and efficient transaction systems, real-time data processing - Education: Learning platforms and mobile apps to enhance educational experiences - Travel & Hospitality: Building booking engines, itinerary planners, and travel apps - Real Estate: Custom property listings, user-friendly property search apps Why Work With Me? - End-to-End Solutions: From ideation and development to testing and deployment - Scalable & Secure Architecture: Applications that grow with your business - Cross-Platform Experience: Expertise in both web and mobile development - Agile & Transparent Communication: Ensuring a smooth collaboration throughout the project What I Can Help You Build - SaaS backends - REST APIs - Microservices architecture - Authentication systems - Payment integrations - Cloud deployment pipelines - Enterprise dashboards If you need a reliable backend engineer to build scalable APIs, SaaS platforms, or cloud-native Java applications, let’s discuss your project. Keywords: Spring Boot, Java Backend, SaaS Development, REST API, Microservices, AWS, Scalable Applications, SaaS Architecture, Platform Engineering, Distributed Systems, Event-Driven Architecture, Cloud-Native Development, Enterprise APIs, Multi-Tenant SaaS, AI Integrations, Kubernetes, Docker, Kafka, DevOps, System Design, Scalable Infrastructure, High Availability Systems, Fintech, Healthcare Platforms, Booking Engines, Real-Time Systems

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At A Glance: J2EE

Developing powerful and dynamic programs and software is a vital aspect of any modern business. Implementing enterprise, networking, and web service software gives businesses an edge when navigating the highly data-driven and interactive business landscape. Java Enterprise Edition is a powerful computing platform for developing enterprise software to help you and your business manage and distribute all aspects of enterprise computations. Java Enterprise Edition provides API platforms for web services, multi-tier architectures, and object-related programming, as well as other powerful and efficient software development tools. Working with Java Enterprise Edition developers and programmers found on Upwork can provide valuable tools and opportunities for you or your organization to take advantage of, thereby creating a dynamic and flexible workspace.

J2EE developers and programmers are highly-skilled computer programmers with experience in the Java scripting language as well as the J2EE development platform. Working with a J2EE developer allows your organization and company to leverage the power of J2EE applications and software solutions that you already have implemented by making applications more efficient and manageable. Programmers can work independently or with a team within your organization to create and develop applications and frameworks your company needs to stay competitive in the highly interactive and data-driven business world. Hiring a freelance J2EE developer or programmer on Upwork gives you and your business access to a highly skilled, flexible pool of talent that is capable of producing a wide variety of solutions and applications that can become the driving force for meeting any enterprising business needs.