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  package org.apache.cayenne.access.jdbc.reader;
  
  import java.sql.ResultSet;
  
  import org.apache.cayenne.CayenneRuntimeException;
  import org.apache.cayenne.DataRow;
  import org.apache.cayenne.access.jdbc.ColumnDescriptor;
  import org.apache.cayenne.access.jdbc.RowDescriptor;
  import org.apache.cayenne.map.DbAttribute;
  import org.apache.cayenne.map.DbEntity;
  import org.apache.cayenne.query.EntityResultSegment;
  import org.apache.cayenne.query.QueryMetadata;
  import org.apache.cayenne.util.Util;
  
  /**
   * @since 3.0
   */
  class IdRowReader<T> extends BaseRowReader<T> {
  
      protected int[] pkIndices;
  
      public IdRowReader(RowDescriptor descriptor, QueryMetadata queryMetadata, EntityResultSegment resultMetadata, DataRowPostProcessor postProcessor) {
          super(descriptor, queryMetadata, postProcessor);
  
          DbEntity dbEntity = resultMetadata == null
                  ? queryMetadata.getDbEntity()
                  : resultMetadata.getClassDescriptor().getEntity().getDbEntity();
          if (dbEntity == null) {
              throw new CayenneRuntimeException("Null root DbEntity, can't index PK");
          }
  
          int len = dbEntity.getPrimaryKeys().size();
  
          // sanity check
          if (len == 0) {
              throw new CayenneRuntimeException("Root DBEntity has no PK defined: %s", dbEntity);
          }
  
          ColumnDescriptor[] columns = descriptor.getColumns();
  
          int[] pk = new int[len];
          int offset = resultMetadata != null ?
                  resultMetadata.getColumnOffset() :
                  0;
          for(int i = offset, j = 0; i < offset + len; i++) {
              DbAttribute a = dbEntity.getAttribute(columns[i].getName());
              if(a != null && a.isPrimaryKey()) {
                  pk[j++] = i;
              }
          }
  
          this.pkIndices = pk;
      }
  
      @Override
      public T readRow(ResultSet resultSet) {
          try {
              if (pkIndices.length == 1) {
                  return readSingleId(resultSet);
              } else {
                  return readIdMap(resultSet);
              }
          } catch (CayenneRuntimeException cex) {
              // rethrow unmodified
              throw cex;
          } catch (Exception otherex) {
              throw new CayenneRuntimeException("Exception materializing id column.", Util.unwindException(otherex));
          }
      }
  
      private T readSingleId(ResultSet resultSet) throws Exception {
  
          // dereference column index
          int index = pkIndices[0];
  
          // note: jdbc column indexes start from 1, not 0 as in arrays
          @SuppressWarnings("unchecked")
          T val = (T) converters[index].materializeObject(resultSet, index + 1, types[index]);
  
          // note that postProcessor overrides are not applied. ID mapping must be
          // the
          // same across inheritance hierarchy, so overrides do not make sense.
          return val;
      }
  
      @SuppressWarnings("unchecked")
      private T readIdMap(ResultSet resultSet) throws Exception {
  
          DataRow idRow = new DataRow(2);
          idRow.setEntityName(entityName);
  
          for (int index : pkIndices) {
              // dereference column index
              // note: jdbc column indexes start from 1, not 0 as in arrays
              Object val = converters[index].materializeObject(resultSet, index + 1, types[index]);
              idRow.put(labels[index], val);
          }
  
          if (postProcessor != null) {
              postProcessor.postprocessRow(resultSet, idRow);
          }
  
          return (T) idRow;
      }
  }
  