reflectiontype

ReflectionType is a term used in reflective programming to denote the runtime representation of a type as exposed by a language’s reflection facilities. A reflection type encapsulates metadata about a type known to the runtime, including its name, kind (such as class, interface, struct, enum, or primitive), visibility and modifiers, base type, implemented interfaces, and, for parameterized types, its type arguments. It also exposes information about members such as fields, properties or attributes, methods, and constructors.

Access to a reflection type enables a program to inspect and interact with types at runtime. Typical capabilities include discovering a type’s name and kind, enumerating its members, creating new instances, invoking methods, reading or writing fields or properties, and examining or applying annotations or attributes. This enables dynamic behavior such as serialization, dependency resolution, and late binding.

Language implementations differ in the specifics of reflection types. In Java, type information is accessed through the java.lang.reflect.Type hierarchy, with implementations like Class and ParameterizedType. In .NET, the Type class serves as the primary reflection type. In dynamic languages such as Python, type objects provide analogous capabilities, while languages with type erasure may expose only partial runtime type information.

Common use cases include serialization frameworks that inspect fields and annotations, object-relational mappers that map types to database schemas, and dependency injection containers that resolve services by type. Limitations include performance overhead from reflective access, potential security restrictions, and incomplete metadata in certain environments. Understanding the exact semantics of reflection types in a given language is crucial for reliable use.

See also: Reflection, Type metadata, Runtime type information, Type system.