Cannot find declaration of element handler-chains Jboss Developer Studio

I resolved the issue by replacing

 <handler-chains xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema">

to

<handler-chains xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
  http://java.sun.com/xml/ns/javaee/javaee_web_services_metadata_handler_2_0.xsd">

I had a similar problem in Eclipse + JDK 1.8 that was resolved by changing the address of the XMLNS attribute.

From:

<javaee:handler-chains xmlns:javaee="http://java.sun.com/xml/ns/javaee" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

To:

<javaee:handler-chains xmlns:javaee="http://xmlns.jcp.org/xml/ns/javaee/" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

See the link below that Oracle has changed the address of the new schemas: http://www.oracle.com/webfolder/technetwork/jsc/xml/ns/javaee/index.html#7