A Config is the unified, read-only view an application queries through ConfigProvider.getConfig(). It aggregates every registered source, applies ordinal precedence, resolves expressions and converts values to the requested type. A Config is obtained per class loader and cached.

A config source is one origin of raw key/value pairs: system properties, environment variables, microprofile-config.properties, or any custom source contributed through the SPI. Each source has an ordinal that defines precedence — higher ordinal wins. See Config Sources.

A converter turns a raw String into a typed value. Ravel ships converters for primitives, boxed types, String, URL, URI, InetAddress, temporal types (Duration, Period), enums, arrays and collections, plus implicit converters for any type exposing a public constructor, valueOf() or parse(). Custom converters are registered through the SPI with a priority. See Type Converters.

A property expression references another configuration value with ${key}, with an optional default via ${key:default}. Expressions are resolved at lookup time and cycle detection prevents infinite loops. See Property Expressions.

A config profile scopes properties to an environment using a %dev., %prod. or %test. prefix. The active profile is selected through mp.config.profile and resolved at lookup time, not build time. See Config Profiles.

In a CDI deployment, configuration values are injected with @ConfigProperty("key") on a bean field — including Optional<T> and Supplier<T> wrappers. Discovery is driven by a Vauban Build Compatible Extension; standalone (non-CDI) use stays available through ConfigProvider.getConfig(). See CDI Integration.

When the same key exists in several sources, the value from the source with the highest ordinal wins. This lets environment variables override packaged defaults, and system properties override both. Precedence is deterministic and computed at lookup.