Towards the understanding and evolution of monolithic applications as microservices

Nowadays, software development teams face the challenge of maintenance and evolution of large applications. This is known as modernization and comprises a process of understanding the existing application, and a process of transforming from the as-is state to the to-be state. In this article, we present an approach to modernize legacy applications into microservices. We propose a model-centered process to analyze and visualize the current structure and dependencies between the business layer and the data layer. Furthermore, we propose a modularization into clusters and microservices using four different diagrams. To validate our approach we have analyzed a JEE application with over 74566 LoC. The results show that the understanding is greatly improved through the diagrams proposed, and the modularization proposed constitutes the first step towards the automated modernization of the application.