Input validation is the process of verifying the supplied data in the request against the contractual definition. Monitor the input validation failures, and to prevent the service quality degradation, consider restricting the access to consumers crossing the failure threshold limit. Developers leverage the JAX-RS 2.1 bean validation features to declaratively specify the validation constraints on an object model. If you need a quick brush up on bean validation support for the JAX-RS resource class, refer to the Introducing validations in JAX-RS application section in Chapter 4, Advanced Features in the JAX-RS API.
You can log the input validation failures for business-critical APIs. This may help you detect malformed and malicious inputs to the application.