code: public static HttpContextActivationFilter getContextActivationFilter(BeanManagerImpl manager, ServletContext context) {
          HttpContextActivationFilter filter = manager.getServices().get(HttpContextActivationFilter.class);
          final String pattern = context.getInitParameter(InitParameters.CONTEXT_MAPPING);
          if (filter == AcceptingHttpContextActivationFilter.INSTANCE) {
              // SPI has precedence. If a filter was not set through SPI let's see if a mapping is set in web.xml
              if (pattern != null) {
                  return new RegexHttpContextActivationFilter(pattern);
              }
          } else if (pattern != null) {
              ServletLogger.LOG.webXmlMappingPatternIgnored(pattern);
          }
          return filter;
      }
docs: Returns the right {@link HttpContextActivationFilter}. If one is set through the SPI it has precedence. Otherwise, if a mapping is set using web.xml, a
  new {@link RegexHttpContextActivationFilter} is constructed and returned. By default, {@link AcceptingHttpContextActivationFilter} is used.
  
  @param manager
  @param context
  @return