RESTEasy can be configured through several configuration options in WAR application deployment file WEB-INF/web.xml. The major one (also portable defined by JAX-RS standard) is javax.ws.rs.Application. When I set this parameter to empty content present behavior is raising exception "java.lang.StringIndexOutOfBoundsException: String index out of range: 0", it is not so good.

I think, this is hard miss-configuration error and deployment description as this one should be rejected and a such application should not be deployed at all with appropriate error message, but not only by messed exception.