Senior Java Application Developer Washington, DC - ONSITE Type: Multi-year Contract US citizenship required per government contract Must be able to obtain Public Trust clearance We seek a Senior Application Developer with Java experience and a strong aptitude in modernizing systems. The incumbent will support up to 3 legacy mission-essential systems in the upgrade from Java/JDK 8 to Java/JDK 21 technology and beyond with operations and maintenance. The Senior Application Developer will leverage knowledge of Object-Oriented Programming, software development methodologies, and the Java language to seamlessly transition our systems to the desired version. The position requires expertise in technologies such as Servlet, JSP, Tag Library, JavaBean, and SQL Server database, invaluable in ensuring smooth and successful migration. Proficiency in tools like Maven, JavaScript, jQuery, Knockout.js, HTML, and CSS is valuable for modernizing the user interface and enhancing the overall user experience. Incumbent must be well-versed in Windows authentication, SSL, session management, and Single Sign-On (SSO) technologies, familiarity with Spring, Spring MVC, and ORM technologies like Hibernate and JPA - these are instrumental in seamlessly integrating the upgraded systems with our existing infrastructure. Familiarity with RESTful web services, JSON parsing, and multipart/form-data file management is highly valued, as is expertise in vulnerability remediation techniques such as CSRF, SQL injection, XSS, and reflection attacks. Upgrade experience: • Previous experience successfully migrating Java applications across multiple major versions • Knowledge of common pitfalls and solutions when upgrading Java applications • Understanding of deprecated features and their modern replacements • Experience identifying and resolving compatibility issues Build, Deployment and CI/CD: • Proficiency with build tools (Maven/Gradle) • Experience updating build pipelines to accommodate newer Java versions • Dependency management skills and handling library compatibility challenges • Experience with continuous integration/continuous deployment (CI/CD) pipelines (Azure DevOps, GitLab) Operations and Maintenance Skills: • Experience with application performance monitoring tools and techniques • Knowledge of log management and analysis systems • Ability to create and maintain runbooks for operational procedures • Proficiency in identifying and resolving production issues • Understanding of JVM tuning and garbage collection optimization • Experience implementing and maintaining automated health checks • Knowledge of security patch management and vulnerability assessment Additional Technical Skills: • Version control with Git • Familiarity with application servers (e.g., Tomcat, WebSphere, WildFly) • Knowledge of common enterprise integrations (SQL Server databases, messaging systems) • Experience with containerization technologies (Docker, Kubernetes) is a plus Soft Skills: • Excellent written and verbal communication skills • Strong problem-solving abilities and attention to detail • Ability to document migration processes, decisions, and technical debt • Self-motivated with the ability to work independently • Collaborative approach when working with existing development teams • Strong time management skills to deliver migration within schedule constraints • Experience providing on-call support and incident management System One, and its subsidiaries including Joulé, ALTA IT Services, and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan. System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law. #M1 #LI-VH1 #DI-VH1 Ref: #851-Rockville-S1 System One, and its subsidiaries including Joulé, ALTA IT Services, CM Access, TPGS, and MOUNTAIN, LTD., are leaders in delivering workforce solutions and integrated services across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible full-time employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan. System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.