code: public static SetAttributeHandler setAttribute(final HttpHandler next, final String attribute, final String value, final ClassLoader classLoader) {
          return new SetAttributeHandler(next, attribute, value, classLoader);
      }
docs: Returns an attribute setting handler that can be used to set an arbitrary attribute on the exchange.
  This includes functions such as adding and removing headers etc.
  
  @param next        The next handler
  @param attribute   The attribute to set, specified as a string presentation of an {@link io.undertow.attribute.ExchangeAttribute}
  @param value       The value to set, specified an a string representation of an {@link io.undertow.attribute.ExchangeAttribute}
  @param classLoader The class loader to use to parser the exchange attributes
  @return The handler