private NetcdfDataset openDataset(
      InvDataset invDataset, boolean acquire, ucar.nc2.util.CancelTask task, Result result)
      throws IOException {

    IOException saveException = null;

    List<InvAccess> accessList =
        new ArrayList<InvAccess>(invDataset.getAccess()); // a list of all the accesses
    while (accessList.size() > 0) {
      InvAccess access = chooseDatasetAccess(accessList);

      // no valid access
      if (access == null) {
        result.errLog.format("No access that could be used in dataset %s %n", invDataset);
        if (saveException != null) throw saveException;
        return null;
      }

      String datasetLocation = access.getStandardUrlName();
      ServiceType serviceType = access.getService().getServiceType();
      if (debugOpen)
        System.out.println("ThreddsDataset.openDataset try " + datasetLocation + " " + serviceType);

      // deal with RESOLVER type
      if (serviceType == ServiceType.RESOLVER) {
        InvDatasetImpl rds = openResolver(datasetLocation, task, result);
        if (rds == null) return null;
        accessList = new ArrayList<InvAccess>(rds.getAccess());
        continue;
      }

      // ready to open it through netcdf API
      NetcdfDataset ds;

      // try to open
      try {
        ds = openDataset(access, acquire, task, result);

      } catch (IOException e) {
        result.errLog.format("Cant open %s %n err=%s%n", datasetLocation, e.getMessage());
        if (debugOpen) {
          System.out.println("Cant open= " + datasetLocation + " " + serviceType);
          e.printStackTrace();
        }

        accessList.remove(access);
        saveException = e;
        continue;
      }

      result.accessUsed = access;
      return ds;
    } // loop over accesses

    if (saveException != null) throw saveException;
    return null;
  }
  private ThreddsDataFactory.Result openFeatureDataset(
      FeatureType wantFeatureType, InvAccess access, ucar.nc2.util.CancelTask task, Result result)
      throws IOException {
    result.featureType = wantFeatureType;
    result.accessUsed = access;

    // special handling for IMAGE
    if (result.featureType == FeatureType.IMAGE) {
      result.imageURL = access.getStandardUrlName();
      result.location = result.imageURL;
      return result;
    }

    if (access.getService().getServiceType() == ServiceType.CdmrFeature) {
      result.featureDataset =
          CdmrFeatureDataset.factory(wantFeatureType, access.getStandardUrlName());

    } else {

      // all other datatypes
      NetcdfDataset ncd = openDataset(access, true, task, result);
      if (null != ncd) {
        result.featureDataset =
            FeatureDatasetFactoryManager.wrap(result.featureType, ncd, task, result.errLog);
      }
    }

    if (null == result.featureDataset) result.fatalError = true;
    else {
      result.location = result.featureDataset.getLocation();
      if ((result.featureType == null) && (result.featureDataset != null))
        result.featureType = result.featureDataset.getFeatureType();
    }

    return result;
  }
  private NetcdfDataset openDataset(
      InvAccess access, boolean acquire, ucar.nc2.util.CancelTask task, Result result)
      throws IOException {
    InvDataset invDataset = access.getDataset();
    String datasetId = invDataset.getID();
    String title = invDataset.getName();

    String datasetLocation = access.getStandardUrlName();
    ServiceType serviceType = access.getService().getServiceType();
    if (debugOpen) System.out.println("ThreddsDataset.openDataset= " + datasetLocation);

    // deal with RESOLVER type
    if (serviceType == ServiceType.RESOLVER) {
      InvDatasetImpl rds = openResolver(datasetLocation, task, result);
      if (rds == null) return null;
      return openDataset(rds, acquire, task, result);
    }

    // ready to open it through netcdf API
    NetcdfDataset ds;

    // open DODS type
    if ((serviceType == ServiceType.OPENDAP) || (serviceType == ServiceType.DODS)) {
      String curl = DODSNetcdfFile.canonicalURL(datasetLocation);
      ds =
          acquire
              ? NetcdfDataset.acquireDataset(curl, enhanceMode, task)
              : NetcdfDataset.openDataset(curl, enhanceMode, task);
    }

    // open CdmRemote
    else if (serviceType == ServiceType.CdmRemote) {
      String curl = CdmRemote.canonicalURL(datasetLocation);
      ds =
          acquire
              ? NetcdfDataset.acquireDataset(curl, enhanceMode, task)
              : NetcdfDataset.openDataset(curl, enhanceMode, task);
    }

    /* open ADDE type
    else if (serviceType == ServiceType.ADDE) {
      try {
        ds = ucar.nc2.adde.AddeDatasetFactory.openDataset(access, task);

      } catch (IOException e) {
        log.append("Cant open as ADDE dataset= "+datasetLocation);
        accessList.remove( access);
        continue;
      }
    } */

    else {
      // open through NetcdfDataset API
      ds =
          acquire
              ? NetcdfDataset.acquireDataset(datasetLocation, enhanceMode, task)
              : NetcdfDataset.openDataset(datasetLocation, enhanceMode, task);
    }

    if (ds != null) {
      ds.setId(datasetId);
      ds.setTitle(title);
      annotate(invDataset, ds);
    }

    // see if there's metadata LOOK whats this
    List list = invDataset.getMetadata(MetadataType.NcML);
    if (list.size() > 0) {
      InvMetadata ncmlMetadata = (InvMetadata) list.get(0);
      NcMLReader.wrapNcML(ds, ncmlMetadata.getXlinkHref(), null);
    }

    result.accessUsed = access;
    return ds;
  }