public interface ParamConverter<T>

Defines a contract for a delegate responsible for converting between a String form of a message parameter value and the corresponding custom Java type T. Conversion of message parameter values injected via @PathParam, @QueryParam, @MatrixParam, @FormParam, @CookieParam and @HeaderParam is supported. API implementations MUST support the ParamConverter mechanism for all Java types. If a ParamConverter is available for a type, it MUST be preferred over all other conversion strategies mentioned in section 3.2 (i.e. single String argument constructor, static valueOf or fromString methods, etc.).

By default, when used for injection of parameter values, a selected ParamConverter instance MUST be used eagerly by an API runtime to convert any default value in the resource or provider model, that is during the application deployment, before any value – default or otherwise – is actually required. This conversion strategy ensures that any errors in the default values are reported as early as possible. This default behavior may be overridden by annotating the ParamConverter implementation class with a @Lazy annotation. In such case any default value conversion delegated to the @Lazy-annotated converter will be deferred to a latest possible moment (i.e. until the injection of such default value is required).

NOTE: A service implementing this contract is not recognized as a registrable extension provider. Instead, a ParamConverterProvider instance responsible for providing ParamConverter instances has to be registered as one of the extension providers.