Configuring a Boot Application

Configuration properties: settings such as a port or a database address that an application reads at startup instead of having them written into its code. A real application needs different settings in different places, a local database on a laptop and a managed one in production, and Spring Boot reads them from several sources in a fixed order. It covers that order, overriding from the command line, profiles for switching whole sets of settings, and @Value compared with @ConfigurationProperties. It leaves out external configuration servers and YAML-specific features.