Legacy Java Application Modernization: A Jakarta EE Migration Guide

Modernizing legacy applications in the cloud era has become an imperative for business success. With customer expectations constantly rising and digital transformation becoming critical for business survival, understanding how to approach legacy application modernization has never been more important.

This blog post is based on our comprehensive legacy application modernization white paper that  you can download for free here.

What Exactly is a Legacy Application?

Contrary to popular belief, a legacy application isn't just old software. According to Gartner, it's "an information system that may be based on outdated technologies, but is critical to day-to-day operations." Interestingly, even relatively modern applications written in Java could be considered legacy if they are built on outdated frameworks like J2EE that are no longer supported.

The True Cost of Legacy Applications

Organizations often underestimate the hidden costs of maintaining legacy systems:

1. Hardware Dependencies: Many legacy systems require specific, often expensive-to-maintain hardware
2. Development Bottlenecks: Simple updates can take weeks or months
3. Security Vulnerabilities: Outdated components pose significant security risks
4. Talent Scarcity: Finding developers for older technologies becomes increasingly difficult
5. Compliance Challenges: Meeting modern regulatory requirements becomes more complex.

The 7 Rs of Legacy Application Modernization

Based on complexity and business impact, organizations can choose from seven modernization approaches. Here's a comprehensive comparison.

A Framework for Successful Modernization

Success in legacy application modernization relies on three key pillars that must work in harmony to ensure effective transformation.

Culture

Organisational culture plays a pivotal role in modernization success. It's essential to create an environment that accepts change while maintaining stability. Start by securing buy-in from all stakeholders, from C-level executives to end-users. Set clear expectations about the modernization journey, including potential challenges and benefits. Prepare your organization for changes in workflows, tools and processes. Remember that resistance to change is natural - address concerns proactively and maintain open communication channels throughout the modernization process.

Portfolio

A strategic approach to portfolio management is crucial for modernization success. Begin by conducting a thorough assessment of your application landscape. Prioritize applications based on business value, technical debt and modernization urgency. Consider your resource constraints carefully - both in terms of budget and expertise. Create a balanced modernization roadmap that combines quick wins to build momentum with longer-term strategic initiatives. Use metrics and KPIs to track progress and demonstrate value to stakeholders.

Technology

While technology choices are important, they should be driven by business needs rather than trends. Carefully evaluate modernization approaches based on your organization's specific context. Consider both current requirements and future scalability needs. Don't fall into the trap of blindly following technology trends - what works for one organization may not work for another. For instance, while microservices are popular, they might not be the best choice for every application. Instead, focus on selecting technologies that align with your team's capabilities and your organisation's long-term technology strategy.

Modernizing Java Enterprise Applications: The Jakarta EE Advantage

A significant portion of enterprise legacy applications are built on Java EE/J2EE platforms, making Jakarta EE a natural modernization path. Jakarta EE (formerly Java EE) represents the evolution of enterprise Java, offering a powerful framework for modernizing legacy applications while maintaining enterprise-grade reliability.

The Java EE to Jakarta EE Modernization Path

The transition from Java EE to Jakarta EE provides several modernization opportunities:

1. Incremental Updates: Move from older Java EE versions (like J2EE) to Jakarta EE 10 in stages, allowing for controlled risk management
2. Cloud-Native Capabilities: Take advantage of Jakarta EE's cloud-native features without completely rewriting your applications
3. Modern Standards: Access updated specifications for REST APIs (JAX-RS or Jakarta REST), persistence (JPA or Jakarta Persistence), and dependency injection (CDI)
4. Microservices Support: Optionally break down monoliths using Jakarta EE's microservices capabilities when it makes business sense.

When to Choose Jakarta EE for Modernization

Jakarta EE is valuable when:

• You have existing Java EE applications that need updating
• Your team has Java expertise
• You need enterprise-grade reliability and security
• You want to modernize without completely rebuilding
• Your application requires strong standards compliance.

The Microservices Myth

While microservices are often touted as the ultimate modernization goal, this isn't always the best approach. Jakarta EE supports both monolithic and microservices architectures effectively. Modern monolithic applications built with Jakarta EE can be just as cloud-native and maintainable as microservices, often with less complexity. The key is choosing an architecture that aligns with your business goals and organizational capabilities.

For example, you might:

• Keep your core application as a Jakarta EE monolith for stability
• Expose new features as Jakarta EE microservices where needed
• Use Jakarta EE's REST capabilities to create modern APIs
• Leverage Jakarta EE's cloud specifications for container deployment.

Practical Example: Modernizing a J2EE Application

Let's look at a practical example of modernizing a J2EE application using different strategies:

1. Retain/Encapsulate Approach:
   • Keep the core J2EE application running
   • Create Jakarta EE REST facades for new functionality
   • Gradually migrate components as needed
2. Replatform Approach:
   • Upgrade from J2EE to Jakarta EE 10
   • Update deprecated APIs to their modern equivalents
   • Maintain existing architecture while gaining modern capabilities
3. Rearchitect Approach:
   • Break down the monolith into Jakarta EE components
   • Implement cloud-native patterns
   • Use Jakarta EE's microservices features where appropriate.

Getting Started 

Before starting on a modernization journey:

1. Assess Current State: Evaluate your application portfolio comprehensively
2. Define Clear Goals: Understand what you want to achieve beyond just "modernization"
3. Start Small: Choose a pilot project with manageable scope
4. Measure Success: Define KPIs to track progress and ROI
5. Plan for Change: Prepare your team for new processes and technologies.

Conclusions

Legacy application modernization is not just about updating technology – it's about transforming your business for the digital age. While the process can be complex, taking a structured approach focused on culture, portfolio and technology can help ensure success. The key is to start with a clear understanding of your goals and choose modernization strategies that align with your organization's capabilities and resources.

Remember, modernization is a journey, not a destination. As technology continues to evolve, maintaining modern, adaptable applications will become increasingly crucial for business success.

Want to learn more about legacy application modernization? Download a copy of "A Business Guide to Legacy Application Modernization For The Cloud Era" and feel free to reach out to discuss your modernization challenges as well as opportunities.