STEP: create a project with JAX-RS support STEP: create a Application class: @ApplicationPath( "/ rest " ) public class A extends Application { } STEP: insert application definition into web.xml as well: <servlet-mapping> <servlet-name>javax.ws.rs.core.Application</servlet-name> <url-pattern>/hello/*</url-pattern> </servlet-mapping> ASSERT: there should be validation warning STEP: comment servlet mapping out in web.xml ASSERT: definition in web.xml should be not taken into account when validating the project, so there should be no validation warning FAIL: there is still validation warning (comment servlet mapping out doesn't affect JAX-RS validator)