Senior Java Developer (#6014) en España, España

N-iX 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 global 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 Project

The 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 reports
• Submit forecasts and operational data
• Access 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 1.1
• STXX (XML/XSLT)
• Ant

Data & Integrations:

• Microsoft SQL Server
• Oracle Database
• Stored Procedures
• LDAP
• SFTP
• Email integrations

Application Size:

• 200,000+ lines of Java code
• Monolithic architecture
• No automated test coverage currently in place

Responsibilities

• Lead and execute the migration of a large legacy Java application
• Upgrade Java versions and modernize the framework stack
• Perform migration from javax to jakarta
• Upgrade dependencies and address security vulnerabilities
• Analyze and refactor legacy code where required
• Create unit and integration tests for existing functionality
• Support regression testing activities
• Collaborate closely with the customer’s technical stakeholders
• Deliver early security improvements and test coverage for critical business flows during the initial project phase

Requirements

Must Have

• 5+ years of commercial experience with Java
• Proven experience working with Struts 1.x
• Experience with Java version upgrades and/or framework migration projects
• Strong knowledge of Apache Tomcat and Linux environments
• Experience working with SQL Server and Oracle databases
• Solid understanding of JDBC and stored procedures
• Experience testing and maintaining legacy applications
• Strong problem-solving and debugging skills
• Fluent spoken and written English
• Based in the EU

Nice to Have

• Experience with AI-assisted migration tools (OpenRewrite, GitHub Copilot, Claude, Gemini, etc.)
• Knowledge of XSLT/XML transformations
• Experience migrating build systems from Ant to Maven or Gradle
• Experience with Azure DevOps
• Experience with large monolithic enterprise applications

We offer*:

• Flexible working format - remote, office-based or flexible
• A competitive salary and good compensation package
• Professional development tools (mentorship program, tech talks and trainings, centers of excellence, and more)
• Active tech communities with regular knowledge sharing