The Spring Framework supports various Kotlin constructs, such as instantiating Kotlin classes through primary constructors, immutable classes data binding, and function optional parameters with default values.

Kotlin parameter names are recognized through a dedicated KotlinReflectionParameterNameDiscoverer, which allows finding interface method parameter names without requiring the Java 8 -parameters compiler flag to be enabled during compilation.

The Jackson Kotlin module, which is required for serializing or deserializing JSON data, is automatically registered when found in the classpath, and a warning message is logged if Jackson and Kotlin are detected without the Jackson Kotlin module being present.

You can declare configuration classes as top level or nested but not inner, since the later requires a reference to the outer class.