Senior Java Developer (#6014)

N-iX LTD; España; Hybrid; EUR 70,000 - 110,000; Full time

Benefits offered by this job

Flexible working format

Competitive salary

Mentorship program

Tech talks and trainings

Job summary

N-iX seeks a Senior Java Developer to join a long-term modernization program for a US-based provider serving Fortune-level clients. You will migrate a large, legacy Java application, upgrade Java versions, and move from javax to jakarta while preserving critical functions.

The role involves upgrading dependencies, addressing security vulnerabilities, and creating tests to ensure stable delivery. Strong English and EU residency are required.

Qualifications

• 5+ years of commercial experience with Java.
• Proven experience with Struts 1.x and Java version upgrades.
• Strong knowledge of Apache Tomcat and Linux environments.
• Experience with SQL Server and Oracle databases; JDBC and stored procedures.
• Experience testing and maintaining legacy applications; debugging skills.
• Fluent English; EU-based location.

Responsibilities

• Lead and execute migration of a large legacy Java application.
• Upgrade Java versions and modernize the framework stack.
• Migrate from javax to jakarta and upgrade dependencies.
• Address security vulnerabilities and refactor legacy code as needed.
• Create unit and integration tests; support regression testing.
• Collaborate with customer stakeholders and ensure timely delivery.

Skills

Java

Struts 1.x

Java upgrades

Tomcat

Linux

SQL Server

Oracle

JDBC

Debugging

English

Tools

Ant

Tomcat

Maven/Gradle

XML/XSLT

XSLT/XML transformations

Job description

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