New Wave of Component Reuse with Spring Framework - AP Case Study

The myth of component reuse has always been the “holy grail” of software engineering. The motivation var-ies from less time, effort and money expenditure to higher system quality and reliability which is especially impor-tant in the domain of high energy physics and accelerator controls. Identified as an issue by D. McIlroy in 1968 [1], it has been generally addressed in many ways with vari-ous success rates. But only recently with the advent of fresh ideas like the Spring Framework with its powerful yet simple “Inversion of Control” paradigm the solution to the problem has started to be surprisingly uncompli-cated. Gathered over years of experience this document explains best practices and lessons learned applied at CERN for the design of the operational software used to control the accelerator complex and focuses on features of the Spring Framework that render the component reuse achievable in practice. It also provides real life use cases of mission-critical control systems developed by the Ap-plication Section like the LHC Software Architecture (LSA), the Injector Control Architecture (InCA) or the Software Interlock System (SIS) that have built their own success mostly upon a stack of reusable software components.