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What is Java application modernization?

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Java™ has been one of the most popular programming languages for enterprise software development for over 27 years. Countless systems around the world have been built using this widely known language.

Traditional Java applications are monoliths. They contain everything needed to run the app in their package, but the monolithic nature makes it difficult for developers to remain agile when making changes. Developers have to essentially take what’s there, recompile it, test it, and redeploy it in order to make a single change. 

With application modernization, developers can bring agility back to legacy applications like those built in Java by migrating them to a modern platform, breaking up monoliths into smaller easier to maintain components like microservices, applying modern software development and deployment practices, and integrating old with new.

Modernizing these applications can help businesses save time and money by updating traditional applications instead of rewriting existing application code. By adopting cloud-native and microservice architecture, developers can make Java applications more efficient and businesses can invest more into future intiatives.

Java applications historically rely on a monolithic architecture, resulting in the need for critical overhead to support and manage over time.  Modernizing Java applications for the cloud and containers is an opportunity to continue driving value from these apps while improving performance, scalability, and cost.

Because of its portability and vast ecosystem, Java has been a favorite choice of enterprise environments for decades because it is object-oriented, platform-independent, stable, and backwards compatible. Java offers a well-defined set of application programming interfaces (APIs), extensive developer tooling, and is easy to learn.

More recently, application development has undergone a critical shift, as developers move away from traditional, monolithic architecture patterns to lighter and more modular services and functions. Often these are built using cloud computing and container orchestration platforms such as Kubernetes. This approach is generally described as "cloud-native Java."

Noting that Java was not originally designed for fast bootup times, low memory footprints, or containers, it has had to evolve. The bright side? The benefits of Java can still be enjoyed in cloud environments with its modernization.


  • Streamlined developer experience: In cloud environments, developers can provision resources in minutes with the push of a button. There are also well integrated tools to configure networking, storage, or other services, which are all pre-configured and ready to go.
  • High availability and cloud provider support: Cloud providers guarantee high availability—supporting service-level agreements (SLAs) that are hard to match in a private datacenter without substantial effort and cost. This makes cloud services an attractive option for anyone wanting to run any type of applications without having to manage their own infrastructure.
  • Scalability and elasticity: Scalability is one of the most important reasons developers move to cloud computing, because it lets them increase or decrease resources on demand, based on changing needs. The same level of scalability in a non-cloud environment would be prohibitively expensive in many cases.
  • Global reach and managed availability zones: Cloud environments enable global reach, providing low-latency services all over the world. Strategically placed datacenters let cloud users extend the reach of their own applications, deploying them to customers in different parts of the world that may not have been previously practical, economical, or even possible.
  • Low cost: Cloud computing does not require a massive upfront expenditure, which saves the incidental costs of running the hardware—such as power, space, and maintenance. Cloud deployment is rapid and painless, and the cloud environment is easy to access and learn, consequently accelerating developer productivity and time to market, which further reduces cost.

A cloud-native java application describes any application or microservice built, deployed, and managed in the cloud, rather than a local machine. This modernized approach to software development helps companies create software that is more flexible and scalable, speeding improvements without sacrificing performance or security. 

Cloud-native Java relies on a number of cloud methodologies to enable development, including:

  • Using containers, rather than virtual machines, to package and isolate applications with their runtime environment. A Java application in a container is ideally bundled with everything it needs to operate, bringing more efficiency, speed, and an improved user experience. Containers make it possible to run Java applications on any number of operating systems in the cloud. 
  • Employing continuous integration and continuous delivery (CI/CD), which uses automation to minimize the need for human intervention and deliver frequent updates to users. A reliable CI/CD pipeline can help ensure that developers working on different branches of an application merge their changes back into a single “trunk” before deployment. It’s a way of using automation to eliminate the time-consuming work of reconciling changes from different individual development environments (IDEs).
  • A DevOps framework, in which development and IT operations approach service delivery with a deeply collaborative set of practices to quickly turn ideas into app improvements. This is especially important in cloud-native development with containers, which provide a unified environment for development, delivery, integration, and automation.

There are a number of approaches to cloud-native Java, including:

Java Virtual Machines in Linux Containers

Java Virtual Machines (JVMs) enable Java programs to run anywhere, including Linux containers. There are several potential configurations in this approach: a hypervisor host OS running on a cloud server in the cloud; a guest OS running on a hypervisor VM; a docker container running on the guest OS; a JVM running Java bytecode on the host CPU inside the docker container; or all containers on the same host sharing a kernel. This approach does have the potential for challenges with memory management in some configurations. 


This approach, supported by frameworks like Quarkus, is more lightweight than others, but does require familiarity with Kubernetes, which it uses to handle cloud tasks. MicroProfile is a vendor-neutral, community-driven specification optimized for microservices architecture and favored for its many integrations with other cloud-native technologies. 

Native Images 

Native image technology allows Java code to be compiled ahead of time in a standalone executable file, delivering benefits like near-instant startup times, low memory usage, and portability between systems. This approach often uses Liberica Native Image Kit (NIK) as its compiler, which translates Java bytecode into binary code, though it can’t optimize every program. Spring Boot 3, which has superseded the experimental Spring Native, is part of the popular Spring framework, and compiles Java applications into executables. 

If you’re interested in pursuing cloud-native Java application development, there are several frameworks that are worth further investigation. Here are a few examples: 

Quarkus is a full-stack, Kubernetes-native Java framework made for JVMs and native compilation, optimizing Java specifically for containers and enabling it to become an effective platform for serverless, cloud, and Kubernetes environments.

Micronaut is a JVM-based framework with a focus on speed and modularity. By performing its dependency injections at compile time, rather than runtime, Micronaut boasts faster startup times and a reduced memory footprint relative to other frameworks.

Spring Cloud Functions is a new version of the longstanding Spring development framework, this time tailored to cloud deployments. Cloud functions in this framework can support a mix of reactive or imperative styles, and are intended to be deployed in any number of ways, from web services to background work.

Eclipse Vert.x offers a variety of tools for building reactive applications on JVMs, enabling them to scale up and down depending on workload requirements. It does this through an emphasis on efficiency, using an asynchronous programming model to handle concurrent workloads using event loops.

Dropwizard is a mature framework known for its stability and its out-of-the-box support for configuration, application metrics, logging, and operational tools, among others. Dropwizard shines when used for revisions to existing applications because its structure plays well with older Java development approaches. 

Finally, both Google and Microsoft have starter Java frameworks available for basic functions, so if your needs are relatively simple, these open-source frameworks might be all you require.

All applications do not need to follow the same modernization path. Developers can choose the path that best fits the characteristics of each application, as well as their organization’s current and expected needs.

With that in mind, if you’re thinking about modernizing your Java applications, moving away from monolithic architectures, and taking true advantage of the cloud deployment model, there are three main paths to Java application modernization: rehost, replatform, and refactor.

Rehost - Virtualization

The rehost path, also known as lift and shift, means to deploy your existing application as is within a virtual machine (VM). The rehost path involves lifting and shifting Java applications running on traditional application servers into VMs running on a hybrid cloud platform. Monolithic applications remain unchanged on your application server and retain all existing integrations and dependencies.

Replatform – Openshift

The replatform path means to deploy your application in a container on a Kubernetes-based cloud platform like Red Hat® OpenShift®.

Replatforming Java applications on OpenShift allows you to take advantage of the functionality inherent in the platform, for example; improved resource usage through bin packing, horizontal scaling, CI/CD integration tooling, integrated monitoring tools and more. OpenShift provides extensive tooling to streamline the process of building and deploying Java application images and also provides the ability to introduce modern cloud native development techniques through the introduction of MicroProfile and content trimming.

Refactor – Openshift Application Foundations

The refactor path means to transform your application into microservices, integrate new technologies, and deploy on a cloud platform. Refactoring involves redeveloping Java application services as microservices deployed within a service mesh on a hybrid cloud platform. Services can be rebuilt over time to gradually move functionality from your old application architecture to your new one. Using the Strangler pattern, monoliths can transform into microservices over time allowing new services to be added while refactoring older services.

Red Hat OpenShift with Application Foundations provides a platform that streamlines execution across the entire application life cycle. The combination enables developers to build, deploy, and operate applications with security in mind and at scale across the hybrid cloud.

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Plan your Java application modernization journey

As an expert in both open source Java and Kubernetes, Red Hat can help you modernize your Java applications and build an agile, cloud-native IT environment to support evolving business demands. We offer a complete, unified, open hybrid cloud foundation for your application modernization journey.

As a trusted development platform for more than 20 years, many businesses rely on Java to power a wide range of experiences. Red Hat has helped countless developers preserve and improve upon existing Java applications, reimagining them for cloud-native environments to deliver new innovations in tested frameworks.

Red Hat platforms give you the flexibility, interoperability, and consistency needed for application modernization. Red Hat OpenShift® is a security-focused hybrid cloud platform that lets you confidently develop, deploy, and manage your applications across environments. Additionally, to assess Java applications for cloud readiness, Red Hat has the Migration Toolkit for Applications (MTA) which provides tools, reports, and knowledge that help developers accelerate application modernization and migration projects.

Contact Red Hat to find out more about application modernization and learn about upcoming events in your area to get hands-on with Red Hat technology.

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