private void verifyStackAndExtensionExist(ExtensionLinkRequest request) throws NoSuchParentResourceException {
    try {
      if (request.getStackName() != null && request.getStackVersion() != null) {
        getManagementController().getAmbariMetaInfo().getStack(request.getStackName(), request.getStackVersion());
      }
      if (request.getExtensionName() != null && request.getExtensionVersion() != null) {
        getManagementController().getAmbariMetaInfo().getExtension(request.getExtensionName(), request.getExtensionVersion());
      }
    }
    catch (AmbariException ambariException) {
      throw new NoSuchParentResourceException(ambariException.getMessage());
    }
  }
The property ids for a ExtensionLink resource.
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/ExtensionLinkResourceProvider.java