code: private String getAliasToFinalize(CMConfigData cmConfigData) {
  
          String alias = null;
          if (cmConfigData == null)
              return alias; // Not expected, but being safe
  
          // Check for DefaultPrincipalMapping alias from res-ref:
          final String DEFAULT_PRINCIPAL_MAPPING = "DefaultPrincipalMapping";
          final String MAPPING_ALIAS = "com.ibm.mapping.authDataAlias";
  
          String loginConfigurationName = cmConfigData.getLoginConfigurationName();
          if ((loginConfigurationName != null) && (!loginConfigurationName.equals(""))) {
              if (loginConfigurationName.equals(DEFAULT_PRINCIPAL_MAPPING)) {
                  HashMap loginConfigProps = cmConfigData.getLoginConfigProperties();
                  if ((loginConfigProps != null) && (!loginConfigProps.isEmpty())) {
                      alias = (String) loginConfigProps.get(MAPPING_ALIAS);
                  }
              }
  
          }
  
          if (alias == null) {
              // Check for container-managed auth alias from CF/DS:
              alias = cmConfigData.getContainerAlias();
          }
  
          return alias;
      }
docs: Get the jaas alias from the config.