If you are looking for Java development services, you probably have one of two problems. Either you are building a backend that has to run for a decade and carry real load, or you own a Java system that has fallen behind and nobody wants to touch. Both are common, and both are solvable without drama. This is how we, a software company in Denmark, approach them, and what to ask any supplier before you sign.
The core points
- Java fits long-lived backends with heavy load and many integrations. It is not the answer to everything.
- Modern Java on an LTS release with Spring Boot is not the Java of its reputation.
- An old Java system rarely needs a rewrite. It needs modernising in small steps.
- Tests come before upgrades. Without them, nobody knows what broke.
- Stay on an LTS release and plan the next upgrade before support ends.
- Pick developers who can read old code, not just write new code.
Where Java development services pay off
Java earns its place where the system is the core of the business and has to last. Order processing, payments, logistics, insurance and public-sector case handling are typical. Three things make it a safe bet there.
Backward compatibility is unusually strong: code written many years ago still runs on newer versions with modest changes. The integration ecosystem is mature, with proven libraries for message queues, databases, SOAP, REST and awkward legacy file formats. And the JVM handles sustained, heavy workloads predictably.
For a small internal tool, a quick prototype or a pure frontend, Java is rarely the best choice. Other stacks get you moving faster.
Modern Java is not the Java people remember
The reputation for sprawling XML configuration and application servers that take minutes to boot belongs to an earlier generation. Today, Java services are usually built with Spring Boot, packaged as containers and deployed like any other service. The language itself has gained records, pattern matching and far less boilerplate.
Java 21 is a long-term support release and brought virtual threads, which make highly concurrent code simpler to write. For business systems, stick to LTS releases. They receive security updates for years, and library maintainers test against them.
Modernising a legacy Java application
Many systems we inherit run on a Java version that no longer gets updates, on a framework nobody in-house knows well. The tempting answer is a rewrite. It is almost always the most expensive and riskiest path.
We work step by step instead:
- Write tests around the behaviour that matters most before changing anything.
- Upgrade the Java version and dependencies in small jumps, one at a time.
- Build new features as separate, bounded services and move traffic away from the old code gradually. This is the strangler pattern.
- Delete old code once nothing calls it any more.
Every step can ship and roll back on its own, and the system keeps running throughout. If you want an honest picture of where you stand first, we start with a code audit.
Integrations are usually the real work
A Java system rarely stands alone. It talks to ERP, payment providers, warehouse systems and partners, often through formats older than the people maintaining them. That is where most surprises hide during a modernisation.
Put a stable interface in front of the old code so other systems never notice what changes behind it. That is classic API development work, and it takes much of the risk out of the whole project.
Choosing a Java partner abroad
Writing a fresh Spring Boot service is the easy part. The hard part is understanding a system that has grown for fifteen years and changing it without breaking anything. So ask a supplier about upgrades, testing existing code and troubleshooting in production, not just greenfield projects.
Ask how knowledge gets written down, too. A Java system outlives most contracts. Working with a Danish team also means overlapping hours with the rest of Europe and contracts under EU law. You can read more about our Java developers.
Frequently asked questions
Yes, for backends that need to run for years under real load. For small tools and prototypes, other languages are often quicker to work with, so choose by the system’s lifespan and requirements.
Rarely. A stepwise modernisation, with tests first, version upgrades and new services alongside the old code, gives the same benefits with much less risk and no long freeze.
The newest LTS release your key libraries and frameworks support. Today that means Java 25, or Java 21 where your frameworks have not caught up. Avoid versions that no longer receive security updates.
Yes. Modern Java with Spring Boot is packaged as containers and runs on all the major cloud platforms. Memory and startup need tuning for the container environment, but that is routine work.
Before you decide
First decide whether Java fits the system’s lifespan and load. If the system already exists, write tests, upgrade in small steps and move features out one at a time rather than starting over. For ongoing work we put a dedicated development team on it as part of our software development services, and day-to-day upkeep falls under software maintenance.
Want us to look at your Java system? Get in touch.
