A RESTEasy application may generate the following error:

The Provider must implement at least one of the following interfaces: javax.ws.rs.ext.MessageBodyReader, javax.ws.rs.ext.MessageBodyWriter, javax.ws.rs.ext.ExceptionMapper or javax.ws.rs.ext.ContextResolver."

To fix the error, select Windows | Preferences. In Preferences, select JBoss Tools | JAX-RS | JAX-RS Validator. Select JAX-RS Providers and set Missing Provider implementation to Ignore, and click on Apply and OK, as shown in the following screenshot: