docs: public I_CmsResourceType getDefaultTypeForName(String resourcename) throws CmsException {
  
          String typeName = null;
          String suffix = null;
          if (CmsStringUtil.isNotEmpty(resourcename)) {
              int pos = resourcename.lastIndexOf('.');
              if (pos >= 0) {
                  suffix = resourcename.substring(pos);
                  if (CmsStringUtil.isNotEmpty(suffix)) {
                      suffix = suffix.toLowerCase();
                      typeName = m_configuration.m_extensionMappings.get(suffix);
  
                  }
              }
          }
  
          if (typeName == null) {
              // use default type "plain"
              typeName = CmsResourceTypePlain.getStaticTypeName();
          }
  
          if (CmsLog.INIT.isDebugEnabled()) {
              CmsLog.INIT.debug(Messages.get().getBundle().key(Messages.INIT_GET_RESTYPE_2, typeName, suffix));
          }
          // look up and return the resource type
          return getResourceType(typeName);
      }