Tutorial Demoiselle 2.5 - M1C2 - ERROR rt.jar unknow

Unknown error for me I'm starting on api REST. :

11:35:51,778 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/calc].[calc.Api]] (http-localhost/127.0.0.1:8080-1) JBWEB000236: Servlet.service() for servlet calc.Api threw exception: org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException
    at org.jboss.resteasy.core.SynchronousDispatcher.handleApplicationException(SynchronousDispatcher.java:364) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.handleException(SynchronousDispatcher.java:232) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.handleInvokerException(SynchronousDispatcher.java:208) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.getResponse(SynchronousDispatcher.java:556) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:523) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:125) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:208) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:55) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:50) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) [jboss-servlet-api_3.0_spec-1.0.2.Final-redhat-2.jar:1.0.2.Final-redhat-2]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:295) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:231) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:149) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:169) [jboss-as-web-7.5.0.Final-redhat-21.jar:7.5.0.Final-redhat-21]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:150) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:97) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:102) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:854) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:653) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:926) [jbossweb-7.5.7.Final-redhat-1.jar:7.5.7.Final-redhat-1]
    at java.lang.Thread.run(Unknown Source) [rt.jar:1.8.0_65]
Caused by: java.lang.NullPointerException
    at calc.CalculatorREST.sum(CalculatorREST.java:13) [classes:]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.8.0_65]
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.8.0_65]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) [rt.jar:1.8.0_65]
    at java.lang.reflect.Method.invoke(Unknown Source) [rt.jar:1.8.0_65]
    at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:168) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.ResourceMethod.invokeOnTarget(ResourceMethod.java:269) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:227) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:216) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.getResponse(SynchronousDispatcher.java:541) [resteasy-jaxrs-2.3.10.Final-redhat-1.jar:]
    ... 19 more

Class CalculatorREST.java

package calc;

import javax.ws.rs.FormParam;
import javax.ws.rs.POST;
import javax.ws.rs.Path;

@Path("calculator")
public class CalculatorREST {

    @POST
    @Path("sum")
    public Integer sum(@FormParam("a") Integer a, @FormParam("b") Integer b) {
        return a + b;
    }
}

Api.java class

package calc;

import javax.ws.rs.ApplicationPath;
import javax.ws.rs.core.Application;

@ApplicationPath("api")
public class Api extends Application{

}