Design patterns, acting as recurring solutions to common problems, offer significant benefits such as avoiding unnecessary complexity, and promoting code reuse, maintainability and extensibility. This paper describes how four not technology-specific or language-specific design patterns (Front Controller, Model View Controller, Transfer Object and Service to Worker) can be applied to one typical e-commerce application developed using Java EE platform. The first goal is to evaluate the improvement of design properties after the implementation of each design pattern using software metrics. Another goal is to assess the influence of design patterns on the maintainability of the e-commerce application under study by examining the evolution of software metrics when performing certain extensions. The results indicate that the application of patterns positively influences design properties such as coupling, complexity and messaging implying a possible improvement in high-level quality attributes such as flexibility, extensibility and reusability.