N-i X is looking for a Senior Java Developer to join a long-term modernization initiative for a large US-based provider of marketing, packaging, print, and supply chain services serving Fortune-level clients worldwide.
You will work within the customer's European supply chain division, supporting warehousing, fulfillment, kitting, and packaging operations for general brands in electronics, medical devices, and consumer products. The main stakeholder is a Software Development Manager who originally built the system and remains deeply involved in its technical evolution.
About the ProjectThe project focuses on a customer-facing web portal that has been operating successfully for over two decades. The portal enables customers, suppliers, and partners to: View inventory, goods, and shipment reportsSubmit forecasts and operational dataAccess supply chain information The system has been in maintenance mode for several years and now requires a strategic technology uplift to address security vulnerabilities and ensure continued support for the next 5–7 years. This is not a rewrite project. The goal is a cost-effective modernization of the existing platform while preserving business-critical functionality. Struts 1.1STXX (XML/XSLT)Ant Data & Integrations: Microsoft SQL ServerOracle DatabaseStored ProceduresLDAPSFTPEmail integrations Application Size:



200,000+ lines of Java codeMonolithic architectureNo automated test coverage currently in place Responsibilities Lead and execute the migration of a large legacy Java applicationUpgrade Java versions and modernize the framework stackPerform migration from javax to jakarta Upgrade dependencies and address security vulnerabilitiesAnalyze and refactor legacy code where requiredCreate unit and integration tests for existing functionalitySupport regression testing activitiesCollaborate closely with the customer’s technical stakeholdersDeliver early security improvements and test coverage for critical business flows during the initial project phase RequirementsMust Have 5+ years of commercial experience with JavaProven experience working with Struts 1.
X Experience with Java version upgrades and/or framework migration projectsStrong knowledge of Apache Tomcat and Linux environmentsExperience working with SQL Server and Oracle databasesSolid understanding of JDBC and stored proceduresExperience testing and maintaining legacy applicationsStrong problem-solving and debugging skillsFluent spoken and written EnglishBased in the EU Nice to Have Experience with AI-assisted migration tools (Open Rewrite, Git Hub Copilot, Claude, Gemini, etc.)Knowledge of XSLT/XML transformationsExperience migrating build systems from Ant to Maven or GradleExperience with Azure Dev OpsExperience with large monolithic enterprise applications

We offer
*: Flexible working format
- remote, office-based or flexibleA competitive salary and good compensation packageProfessional development tools (mentorship program, tech talks and trainings, centers of excellence, and more)Active tech communities with regular knowledge sharing

📌 Senior Java Developer (España)
🏢 N-iX
📍 España