runtimeonly

runtimeOnly is a dependency configuration in Gradle that marks dependencies needed at runtime but not for compiling the source code. Dependencies added to runtimeOnly are not on the compile classpath and are not exported to consumers of a library project. Instead, they are included on the runtime classpath when the application or tests are executed.

This configuration is useful for libraries that must load certain components only during execution, such as database drivers, native libraries, or optional modules that are discovered at runtime. By separating runtime requirements from compile-time ones, build scripts can keep the compile classpath lean and avoid leaking implementation details to consumers.

In practice, you declare runtimeOnly dependencies in the dependencies block. Examples:

- In the Groovy DSL: dependencies { runtimeOnly 'org.postgresql:postgresql:42.2.5' }

- In the Kotlin DSL: dependencies { runtimeOnly("org.postgresql:postgresql:42.2.5") }

Gradle also provides other configurations for different purposes, such as api, implementation, and compileOnly, to control visibility and packaging of dependencies. When publishing libraries, runtimeOnly dependencies are generally not exposed as part of the public API, helping to keep published metadata focused on compile- and API-usable surfaces.