Senior Java Developer – Java Upgrade & Migration

Industry: Insurance / Financial Services

Contract: Freelance / Temporary Assignment

Duration: Contract until end of year, with a strong possibility of extension

Start: ASAP

About the Role

A leading organization in the insurance industry is looking for experienced Java Developers to support a major technical upgrade of its existing application landscape.

The main objective is to modernize and upgrade legacy Java applications running on older Java versions, starting from Java 7, toward modern Java versions up to Java 21+.

This position requires strong hands-on Core Java expertise, particularly in upgrading and migrating existing applications while identifying and resolving compatibility, dependency, performance, and technical issues.

Key Responsibilities

- Upgrade existing Java applications from legacy Java versions to modern Java versions (Java 7 → Java 21+)
- Perform Java application migration and modernization
- Analyze existing legacy Java codebases and identify upgrade requirements
- Resolve compatibility issues, dependencies, deprecated APIs, and technical blockers
- Troubleshoot complex application issues throughout the migration process




- Refactor and adapt existing code where required
- Ensure application stability and functionality following upgrades
- Collaborate with development and infrastructure teams throughout the modernization process
- Support testing, deployment, and technical validation of upgraded applications
- Contribute to containerized deployments where relevant

Required Skills

- Expert-level Core Java knowledge
- Strong hands-on experience across multiple Java versions, ideally Java 7, 8, 11, 17 and/or 21+
- Expert experience with Java upgrades and migrations
- Strong experience working with legacy Java applications
- Excellent analysis and troubleshooting capabilities
- Ability to understand and modernize existing enterprise applications
- Experience resolving technical and compatibility issues during application upgrades
- Strong hands-on software development background

Strong Assets

Experience with the following technologies is highly valuable:

- Tomcat
- OpenShift
- Kubernetes
- Containerized Java environments
- Enterprise Java application modernization

Languages

Candidates must have:

- French OR Dutch
- English

📌 Java developer – java upgrade & migration (España)
🏢 Sparagus
📍 España