Migration of legacy applications and services to Service-Oriented Architecture (SOA)

Service Oriented Architecture (SOA) is becoming a mainstream approach for designing and integrating enterprise applications. This paper presents a methodology for migration of legacy applications and services to Service-Oriented Architecture. In order to upgrade existing applications and services to SOA, the methodology should be used in a consistent functional and technological manner. In addition, we have proposed a specific SOA migration approach based on multi-tier architecture. This architecture brings clear differentiation of logical and technical components, allowing business process to be defined in a flexible and agile manner. The architecture highlights position and role of legacy application, fine and coarse grained services with the respect to their role in the business process. As a critical component in the overall architecture, Enterprise Service Bus acts as mediation and virtualization layer helping to separate business and logical view of the process from its technological implementation and reduce dependencies. Our approach is based on analysis of the legacy software in order to identify the business and presentation logic components. The next step is to redesign the legacy code by isolating the business logic and performing code stripping. Finally coarse-grained and loosely coupled SOA services in the medium and upper layer are created in order to achieve the benefits of SOA architecture.