org.eclipse.mdm.api.odsadapter/src/main/java/org/eclipse/mdm/api/odsadapter/ReadRequestHandler.java - mdmbl/org.eclipse.mdm - Git at Google

 /********************************************************************************
  * Copyright (c) 2015-2019 Contributors to the Eclipse Foundation
  *
  * See the NOTICE file(s) distributed with this work for additional
  * information regarding copyright ownership.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v. 2.0 which is available at
  * http://www.eclipse.org/legal/epl-2.0.
  *
  * SPDX-License-Identifier: EPL-2.0
  *
  ********************************************************************************/

 package org.eclipse.mdm.api.odsadapter;

 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;

 import org.apache.commons.lang3.tuple.ImmutablePair;
 import org.apache.commons.lang3.tuple.Pair;
 import org.asam.ods.AoException;
 import org.asam.ods.Column;
 import org.asam.ods.ElemId;
 import org.asam.ods.NameValueSeqUnit;
 import org.asam.ods.T_LONGLONG;
 import org.asam.ods.ValueMatrix;
 import org.asam.ods.ValueMatrixMode;
 import org.eclipse.mdm.api.base.adapter.Attribute;
 import org.eclipse.mdm.api.base.adapter.EntityType;
 import org.eclipse.mdm.api.base.massdata.ReadRequest;
 import org.eclipse.mdm.api.base.massdata.ReadRequest.ValuesMode;
 import org.eclipse.mdm.api.base.model.AxisType;
 import org.eclipse.mdm.api.base.model.Channel;
 import org.eclipse.mdm.api.base.model.Entity;
 import org.eclipse.mdm.api.base.model.MeasuredValues;
 import org.eclipse.mdm.api.base.model.SequenceRepresentation;
 import org.eclipse.mdm.api.base.model.Unit;
 import org.eclipse.mdm.api.base.model.Value;
 import org.eclipse.mdm.api.base.query.ComparisonOperator;
 import org.eclipse.mdm.api.base.query.DataAccessException;
 import org.eclipse.mdm.api.base.query.Filter;
 import org.eclipse.mdm.api.base.query.Query;
 import org.eclipse.mdm.api.base.query.QueryService;
 import org.eclipse.mdm.api.base.query.Result;
 import org.eclipse.mdm.api.odsadapter.query.ODSEntityType;
 import org.eclipse.mdm.api.odsadapter.query.ODSModelManager;
 import org.eclipse.mdm.api.odsadapter.utils.ODSConverter;

 import com.google.common.collect.Lists;

 /**
  * Reads mass data specified in {@link ReadRequest}s.
  *
  * @since 1.0.0
  * @author Viktor Stoehr, Gigatronik Ingolstadt GmbH
  */
 public final class ReadRequestHandler {
 	public static final class ColumnAttributes {
 		private String name;
 		private SequenceRepresentation sequenceRepresentation;
 		private double[] generationParameters;
 		private boolean independent;
 		private AxisType axisType;

 		public ColumnAttributes(String name, SequenceRepresentation sequenceRepresentation,
 				double[] generationParameters, boolean independent, AxisType axisType) {
 			this.name = name;
 			this.sequenceRepresentation = sequenceRepresentation;
 			this.generationParameters = generationParameters;
 			this.independent = independent;
 			this.axisType = axisType;
 		}

 		public String getName() {
 			return name;
 		}

 		public void setName(String name) {
 			this.name = name;
 		}

 		public SequenceRepresentation getSequenceRepresentation() {
 			return sequenceRepresentation;
 		}

 		public void setSequenceRepresentation(SequenceRepresentation sequenceRepresentation) {
 			this.sequenceRepresentation = sequenceRepresentation;
 		}

 		public double[] getGenerationParameters() {
 			return generationParameters;
 		}

 		public void setGenerationParameters(double[] generationParameters) {
 			this.generationParameters = generationParameters;
 		}

 		public boolean isIndependentColumn() {
 			return independent;
 		}

 		public void setIndependentColumn(boolean independent) {
 			this.independent = independent;
 		}

 		public AxisType getAxisType() {
 			return axisType;
 		}

 		public void setAxisType(AxisType axisType) {
 			this.axisType = axisType;
 		}

 	}

 	// ======================================================================
 	// Instance variables
 	// ======================================================================

 	private final ODSModelManager modelManager;
 	private final QueryService queryService;

 	// ======================================================================
 	// Constructors
 	// ======================================================================

 	/**
 	 * Constructor.
 	 *
 	 * @param modelManager Used to gain access to value matrices.
 	 */
 	public ReadRequestHandler(ODSModelManager modelManager, QueryService queryService) {
 		this.modelManager = modelManager;
 		this.queryService = queryService;
 	}

 	// ======================================================================
 	// Public methods
 	// ======================================================================

 	/**
 	 * Loads {@link MeasuredValues} as defined in given {@link ReadRequest}.
 	 *
 	 * @param readRequest The {@code MeasuredValues} request configuration.
 	 * @return The loaded {@code MeasuredValues} are returned.
 	 * @throws DataAccessException Thrown if unable to load {@code
 	 * 		MeasuredValues}     .
 	 */
 	public List<MeasuredValues> execute(ReadRequest readRequest) throws DataAccessException {
 		ValueMatrix valueMatrix = null;
 		Column[] arrColumns = null;

 		try {
 			valueMatrix = getValueMatrix(readRequest);
 			List<Pair<Column, ColumnAttributes>> listColumnPairs = getODSColumns(readRequest, valueMatrix);

 			arrColumns = listColumnPairs.stream().map(Pair::getLeft).toArray(Column[]::new);
 			ColumnAttributes[] arrColumnAttributes = listColumnPairs.stream().map(Pair::getRight)
 					.toArray(ColumnAttributes[]::new);

 			NameValueSeqUnit[] nvsus = valueMatrix.getValue(arrColumns, readRequest.getStartIndex(),
 					readRequest.getRequestSize());
 			return ODSConverter.fromODSMeasuredValuesSeq(nvsus, arrColumnAttributes);
 		} catch (AoException aoe) {
 			throw new DataAccessException(aoe.reason, aoe);
 		} finally {
 			releaseColumns(arrColumns);
 			releaseValueMatrix(valueMatrix);
 		}
 	}

 	// ======================================================================
 	// Private methods
 	// ======================================================================

 	/**
 	 * Loads all for each defined {@link Channel} in given {@link ReadRequest} and
 	 * loads the corresponding {@link Column} using given {@link ValueMatrix}.
 	 *
 	 * @param readRequest Defines required {@code Column}s.
 	 * @param valueMatrix Used to load required {@code Column}s.
 	 * @return {@code Column} configured in given {@code ReadRequest} are returned
 	 *         with defined {@link Unit} setup.
 	 * @throws AoException         Throw if unable to load all available
 	 *                             {@code Column}s.
 	 * @throws DataAccessException Thrown on wrong {@code ReadRequest} setup.
 	 */
 	private List<Pair<Column, ColumnAttributes>> getODSColumns(ReadRequest readRequest, ValueMatrix valueMatrix)
 			throws AoException, DataAccessException {
 		List<Pair<Column, ColumnAttributes>> listColumnPairs = new ArrayList<>();
 		Map<String, Column> mapColumns = new HashMap<>();

 		try {
 			if (readRequest.isLoadAllChannels()) {
 				// TODO should it be possible to overwrite the unit of some
 				// channels?!
 				// -> this results in a performance issue since we need to call
 				// getName()
 				// on each column for mapping! (no longer, see below!)
 				Column[] columns = valueMatrix.getColumns("*");

 				if (null != columns) {
 					for (Column column : columns) {
 						String columnName = column.getName();
 						if (mapColumns.containsKey(columnName)) {
 							releaseColumns(columns);
 							throw new DataAccessException(
 									String.format("Duplicate column name '%s' found within submatrix ID %d!",
 											columnName, Long.valueOf(readRequest.getChannelGroup().getID())));
 						}

 						mapColumns.put(columnName, column);
 					}
 				}
 			} else {
 				for (Entry<Channel, Unit> entry : readRequest.getChannels().entrySet()) {
 					Channel channel = entry.getKey();
 					Unit unit = entry.getValue();
 					String channelName = channel.getName();
 					Column[] columns = valueMatrix.getColumns(channelName);
 					if (columns == null || columns.length != 1) {
 						releaseColumns(columns);
 						throw new DataAccessException(String.format(
 								"Zero or more than one column with name '%s' found within submatrix ID %d!",
 								channelName, Long.valueOf(readRequest.getChannelGroup().getID())));
 					}

 					Column column = columns[0];
 					if (!unit.nameEquals(channel.getUnit().getName())) {
 						column.setUnit(unit.getName());
 					}

 					mapColumns.put(channelName, column);
 				}
 			}

 			if (mapColumns.size() > 0) {
 				EntityType localColumnEntityType = modelManager.getEntityType("LocalColumn");
 				Attribute idAttr = localColumnEntityType.getAttribute("Id");
 				Attribute nameAttr = localColumnEntityType.getAttribute("Name");
 				Attribute submatrixAttr = localColumnEntityType.getAttribute("SubMatrix");

 				// Don't query GenerationParameters together with other non-ID attributes as
 				// Avalon dislikes this:
 				Query query1 = queryService.createQuery()
 						.select(Lists.newArrayList(idAttr, nameAttr,
 								localColumnEntityType.getAttribute("SequenceRepresentation"),
 								localColumnEntityType.getAttribute("IndependentFlag"),
 								localColumnEntityType.getAttribute("axistype")));

 				Filter filter = Filter.and().add(ComparisonOperator.EQUAL.create(submatrixAttr,
 						Long.valueOf(readRequest.getChannelGroup().getID())));

 				Set<String> setColumnNames = mapColumns.keySet();

 				Map<String, ColumnAttributes> mapColumnAttributes = new HashMap<>();

 				for (Result result : query1.fetch(filter)) {
 					Map<String, Value> mapValues = result.getRecord(localColumnEntityType).getValues();

 					String columnName = mapValues.get("Name").extract();

 					if (setColumnNames.contains(columnName)) {
 						ColumnAttributes ca = new ColumnAttributes(columnName,
 								(ValuesMode.CALCULATED == readRequest.getValuesMode() ? SequenceRepresentation.EXPLICIT
 										: mapValues.get("SequenceRepresentation").extract()),
 								new double[0], ((short) mapValues.get("IndependentFlag").extract() != 0),
 								mapValues.get("axistype").extract());

 						mapColumnAttributes.put(mapValues.get("Id").extract(), ca);
 					}
 				}

 				if (ValuesMode.CALCULATED != readRequest.getValuesMode()) {
 					Query query2 = queryService.createQuery().select(idAttr,
 							localColumnEntityType.getAttribute("GenerationParameters"));

 					for (Result result : query2.fetch(filter)) {
 						Map<String, Value> mapValues = result.getRecord(localColumnEntityType).getValues();

 						ColumnAttributes ca = mapColumnAttributes.get(mapValues.get("Id").extract());

 						if (ca != null) {
 							ca.setGenerationParameters(mapValues.get("GenerationParameters").extract());
 						}
 					}
 				}

 				for (Map.Entry<String, ColumnAttributes> me : mapColumnAttributes.entrySet()) {
 					ColumnAttributes ca = me.getValue();
 					listColumnPairs.add(new ImmutablePair<Column, ColumnAttributes>(mapColumns.get(ca.getName()), ca));
 				}
 			}

 			return listColumnPairs;
 		} catch (AoException e) {
 			releaseColumns(listColumnPairs.stream().map(Pair::getLeft).toArray(Column[]::new));
 			throw new DataAccessException("Unable to load column due to: " + e.reason, e);
 		}
 	}

 	/**
 	 * Returns the {@link ValueMatrix} CORBA service object associated with given
 	 * {@link ReadRequest}.
 	 *
 	 * @param readRequest The {@code ReadRequest}.
 	 * @return The {@code ValueMatrix} is returned.
 	 * @throws AoException Thrown if unable to load the {@code ValueMatrix}.
 	 */
 	private ValueMatrix getValueMatrix(ReadRequest readRequest) throws AoException {
 		Entity entity = readRequest.getChannelGroup();
 		T_LONGLONG iid = ODSConverter.toODSID(entity.getID());
 		T_LONGLONG aid = ((ODSEntityType) modelManager.getEntityType(entity)).getODSID();
 		ValueMatrixMode valueMatrixMode = ValueMatrixMode.CALCULATED;
 		switch (readRequest.getValuesMode()) {
 		case CALCULATED:
 			valueMatrixMode = ValueMatrixMode.CALCULATED;
 			break;
 		case STORAGE:
 			valueMatrixMode = ValueMatrixMode.STORAGE;
 			break;
 		default:
 			throw new DataAccessException(
 					String.format("Unsupported ValueMode %s!", readRequest.getValuesMode().name()));
 		}

 		return modelManager.getApplElemAccess().getValueMatrixInMode(new ElemId(aid, iid), valueMatrixMode);
 	}

 	/**
 	 * Releases given {@link ValueMatrix} CORBA object.
 	 *
 	 * @param valueMatrix Will be released.
 	 */
 	private void releaseValueMatrix(ValueMatrix valueMatrix) {
 		if (valueMatrix == null) {
 			return;
 		}

 		try {
 			valueMatrix.destroy();
 		} catch (AoException aoe) {
 			// ignore
 		} finally {
 			valueMatrix._release();
 		}
 	}

 	/**
 	 * Releases each CORBA {@link Column} object.
 	 *
 	 * @param columns Will be released.
 	 */
 	private void releaseColumns(Column[] columns) {
 		if (columns == null) {
 			return;
 		}

 		for (Column column : columns) {
 			try {
 				column.destroy();
 			} catch (AoException e) {
 				// ignore
 			} catch (Exception e) {
 				// ignore
 			} finally {
 				column._release();
 			}
 		}
 	}

 }
	/********************************************************************************
	* Copyright (c) 2015-2019 Contributors to the Eclipse Foundation
	*
	* See the NOTICE file(s) distributed with this work for additional
	* information regarding copyright ownership.
	*
	* This program and the accompanying materials are made available under the
	* terms of the Eclipse Public License v. 2.0 which is available at
	* http://www.eclipse.org/legal/epl-2.0.
	*
	* SPDX-License-Identifier: EPL-2.0
	*
	********************************************************************************/

	package org.eclipse.mdm.api.odsadapter;

	import java.util.ArrayList;
	import java.util.HashMap;
	import java.util.List;
	import java.util.Map;
	import java.util.Map.Entry;
	import java.util.Set;

	import org.apache.commons.lang3.tuple.ImmutablePair;
	import org.apache.commons.lang3.tuple.Pair;
	import org.asam.ods.AoException;
	import org.asam.ods.Column;
	import org.asam.ods.ElemId;
	import org.asam.ods.NameValueSeqUnit;
	import org.asam.ods.T_LONGLONG;
	import org.asam.ods.ValueMatrix;
	import org.asam.ods.ValueMatrixMode;
	import org.eclipse.mdm.api.base.adapter.Attribute;
	import org.eclipse.mdm.api.base.adapter.EntityType;
	import org.eclipse.mdm.api.base.massdata.ReadRequest;
	import org.eclipse.mdm.api.base.massdata.ReadRequest.ValuesMode;
	import org.eclipse.mdm.api.base.model.AxisType;
	import org.eclipse.mdm.api.base.model.Channel;
	import org.eclipse.mdm.api.base.model.Entity;
	import org.eclipse.mdm.api.base.model.MeasuredValues;
	import org.eclipse.mdm.api.base.model.SequenceRepresentation;
	import org.eclipse.mdm.api.base.model.Unit;
	import org.eclipse.mdm.api.base.model.Value;
	import org.eclipse.mdm.api.base.query.ComparisonOperator;
	import org.eclipse.mdm.api.base.query.DataAccessException;
	import org.eclipse.mdm.api.base.query.Filter;
	import org.eclipse.mdm.api.base.query.Query;
	import org.eclipse.mdm.api.base.query.QueryService;
	import org.eclipse.mdm.api.base.query.Result;
	import org.eclipse.mdm.api.odsadapter.query.ODSEntityType;
	import org.eclipse.mdm.api.odsadapter.query.ODSModelManager;
	import org.eclipse.mdm.api.odsadapter.utils.ODSConverter;

	import com.google.common.collect.Lists;

	/**
	* Reads mass data specified in {@link ReadRequest}s.
	*
	* @since 1.0.0
	* @author Viktor Stoehr, Gigatronik Ingolstadt GmbH
	*/
	public final class ReadRequestHandler {
	public static final class ColumnAttributes {
	private String name;
	private SequenceRepresentation sequenceRepresentation;
	private double[] generationParameters;
	private boolean independent;
	private AxisType axisType;

	public ColumnAttributes(String name, SequenceRepresentation sequenceRepresentation,
	double[] generationParameters, boolean independent, AxisType axisType) {
	this.name = name;
	this.sequenceRepresentation = sequenceRepresentation;
	this.generationParameters = generationParameters;
	this.independent = independent;
	this.axisType = axisType;
	}

	public String getName() {
	return name;
	}

	public void setName(String name) {
	this.name = name;
	}

	public SequenceRepresentation getSequenceRepresentation() {
	return sequenceRepresentation;
	}

	public void setSequenceRepresentation(SequenceRepresentation sequenceRepresentation) {
	this.sequenceRepresentation = sequenceRepresentation;
	}

	public double[] getGenerationParameters() {
	return generationParameters;
	}

	public void setGenerationParameters(double[] generationParameters) {
	this.generationParameters = generationParameters;
	}

	public boolean isIndependentColumn() {
	return independent;
	}

	public void setIndependentColumn(boolean independent) {
	this.independent = independent;
	}

	public AxisType getAxisType() {
	return axisType;
	}

	public void setAxisType(AxisType axisType) {
	this.axisType = axisType;
	}

	}

	// ======================================================================
	// Instance variables
	// ======================================================================

	private final ODSModelManager modelManager;
	private final QueryService queryService;

	// ======================================================================
	// Constructors
	// ======================================================================

	/**
	* Constructor.
	*
	* @param modelManager Used to gain access to value matrices.
	*/
	public ReadRequestHandler(ODSModelManager modelManager, QueryService queryService) {
	this.modelManager = modelManager;
	this.queryService = queryService;
	}

	// ======================================================================
	// Public methods
	// ======================================================================

	/**
	* Loads {@link MeasuredValues} as defined in given {@link ReadRequest}.
	*
	* @param readRequest The {@code MeasuredValues} request configuration.
	* @return The loaded {@code MeasuredValues} are returned.
	* @throws DataAccessException Thrown if unable to load {@code
	* MeasuredValues} .
	*/
	public List<MeasuredValues> execute(ReadRequest readRequest) throws DataAccessException {
	ValueMatrix valueMatrix = null;
	Column[] arrColumns = null;

	try {
	valueMatrix = getValueMatrix(readRequest);
	List<Pair<Column, ColumnAttributes>> listColumnPairs = getODSColumns(readRequest, valueMatrix);

	arrColumns = listColumnPairs.stream().map(Pair::getLeft).toArray(Column[]::new);
	ColumnAttributes[] arrColumnAttributes = listColumnPairs.stream().map(Pair::getRight)
	.toArray(ColumnAttributes[]::new);

	NameValueSeqUnit[] nvsus = valueMatrix.getValue(arrColumns, readRequest.getStartIndex(),
	readRequest.getRequestSize());
	return ODSConverter.fromODSMeasuredValuesSeq(nvsus, arrColumnAttributes);
	} catch (AoException aoe) {
	throw new DataAccessException(aoe.reason, aoe);
	} finally {
	releaseColumns(arrColumns);
	releaseValueMatrix(valueMatrix);
	}
	}

	// ======================================================================
	// Private methods
	// ======================================================================

	/**
	* Loads all for each defined {@link Channel} in given {@link ReadRequest} and
	* loads the corresponding {@link Column} using given {@link ValueMatrix}.
	*
	* @param readRequest Defines required {@code Column}s.
	* @param valueMatrix Used to load required {@code Column}s.
	* @return {@code Column} configured in given {@code ReadRequest} are returned
	* with defined {@link Unit} setup.
	* @throws AoException Throw if unable to load all available
	* {@code Column}s.
	* @throws DataAccessException Thrown on wrong {@code ReadRequest} setup.
	*/
	private List<Pair<Column, ColumnAttributes>> getODSColumns(ReadRequest readRequest, ValueMatrix valueMatrix)
	throws AoException, DataAccessException {
	List<Pair<Column, ColumnAttributes>> listColumnPairs = new ArrayList<>();
	Map<String, Column> mapColumns = new HashMap<>();

	try {
	if (readRequest.isLoadAllChannels()) {
	// TODO should it be possible to overwrite the unit of some
	// channels?!
	// -> this results in a performance issue since we need to call
	// getName()
	// on each column for mapping! (no longer, see below!)
	Column[] columns = valueMatrix.getColumns("*");

	if (null != columns) {
	for (Column column : columns) {
	String columnName = column.getName();
	if (mapColumns.containsKey(columnName)) {
	releaseColumns(columns);
	throw new DataAccessException(
	String.format("Duplicate column name '%s' found within submatrix ID %d!",
	columnName, Long.valueOf(readRequest.getChannelGroup().getID())));
	}

	mapColumns.put(columnName, column);
	}
	}
	} else {
	for (Entry<Channel, Unit> entry : readRequest.getChannels().entrySet()) {
	Channel channel = entry.getKey();
	Unit unit = entry.getValue();
	String channelName = channel.getName();
	Column[] columns = valueMatrix.getColumns(channelName);
	if (columns == null \|\| columns.length != 1) {
	releaseColumns(columns);
	throw new DataAccessException(String.format(
	"Zero or more than one column with name '%s' found within submatrix ID %d!",
	channelName, Long.valueOf(readRequest.getChannelGroup().getID())));
	}

	Column column = columns[0];
	if (!unit.nameEquals(channel.getUnit().getName())) {
	column.setUnit(unit.getName());
	}

	mapColumns.put(channelName, column);
	}
	}

	if (mapColumns.size() > 0) {
	EntityType localColumnEntityType = modelManager.getEntityType("LocalColumn");
	Attribute idAttr = localColumnEntityType.getAttribute("Id");
	Attribute nameAttr = localColumnEntityType.getAttribute("Name");
	Attribute submatrixAttr = localColumnEntityType.getAttribute("SubMatrix");

	// Don't query GenerationParameters together with other non-ID attributes as
	// Avalon dislikes this:
	Query query1 = queryService.createQuery()
	.select(Lists.newArrayList(idAttr, nameAttr,
	localColumnEntityType.getAttribute("SequenceRepresentation"),
	localColumnEntityType.getAttribute("IndependentFlag"),
	localColumnEntityType.getAttribute("axistype")));

	Filter filter = Filter.and().add(ComparisonOperator.EQUAL.create(submatrixAttr,
	Long.valueOf(readRequest.getChannelGroup().getID())));

	Set<String> setColumnNames = mapColumns.keySet();

	Map<String, ColumnAttributes> mapColumnAttributes = new HashMap<>();

	for (Result result : query1.fetch(filter)) {
	Map<String, Value> mapValues = result.getRecord(localColumnEntityType).getValues();

	String columnName = mapValues.get("Name").extract();

	if (setColumnNames.contains(columnName)) {
	ColumnAttributes ca = new ColumnAttributes(columnName,
	(ValuesMode.CALCULATED == readRequest.getValuesMode() ? SequenceRepresentation.EXPLICIT
	: mapValues.get("SequenceRepresentation").extract()),
	new double[0], ((short) mapValues.get("IndependentFlag").extract() != 0),
	mapValues.get("axistype").extract());

	mapColumnAttributes.put(mapValues.get("Id").extract(), ca);
	}
	}

	if (ValuesMode.CALCULATED != readRequest.getValuesMode()) {
	Query query2 = queryService.createQuery().select(idAttr,
	localColumnEntityType.getAttribute("GenerationParameters"));

	for (Result result : query2.fetch(filter)) {
	Map<String, Value> mapValues = result.getRecord(localColumnEntityType).getValues();

	ColumnAttributes ca = mapColumnAttributes.get(mapValues.get("Id").extract());

	if (ca != null) {
	ca.setGenerationParameters(mapValues.get("GenerationParameters").extract());
	}
	}
	}

	for (Map.Entry<String, ColumnAttributes> me : mapColumnAttributes.entrySet()) {
	ColumnAttributes ca = me.getValue();
	listColumnPairs.add(new ImmutablePair<Column, ColumnAttributes>(mapColumns.get(ca.getName()), ca));
	}
	}

	return listColumnPairs;
	} catch (AoException e) {
	releaseColumns(listColumnPairs.stream().map(Pair::getLeft).toArray(Column[]::new));
	throw new DataAccessException("Unable to load column due to: " + e.reason, e);
	}
	}

	/**
	* Returns the {@link ValueMatrix} CORBA service object associated with given
	* {@link ReadRequest}.
	*
	* @param readRequest The {@code ReadRequest}.
	* @return The {@code ValueMatrix} is returned.
	* @throws AoException Thrown if unable to load the {@code ValueMatrix}.
	*/
	private ValueMatrix getValueMatrix(ReadRequest readRequest) throws AoException {
	Entity entity = readRequest.getChannelGroup();
	T_LONGLONG iid = ODSConverter.toODSID(entity.getID());
	T_LONGLONG aid = ((ODSEntityType) modelManager.getEntityType(entity)).getODSID();
	ValueMatrixMode valueMatrixMode = ValueMatrixMode.CALCULATED;
	switch (readRequest.getValuesMode()) {
	case CALCULATED:
	valueMatrixMode = ValueMatrixMode.CALCULATED;
	break;
	case STORAGE:
	valueMatrixMode = ValueMatrixMode.STORAGE;
	break;
	default:
	throw new DataAccessException(
	String.format("Unsupported ValueMode %s!", readRequest.getValuesMode().name()));
	}

	return modelManager.getApplElemAccess().getValueMatrixInMode(new ElemId(aid, iid), valueMatrixMode);
	}

	/**
	* Releases given {@link ValueMatrix} CORBA object.
	*
	* @param valueMatrix Will be released.
	*/
	private void releaseValueMatrix(ValueMatrix valueMatrix) {
	if (valueMatrix == null) {
	return;
	}

	try {
	valueMatrix.destroy();
	} catch (AoException aoe) {
	// ignore
	} finally {
	valueMatrix._release();
	}
	}

	/**
	* Releases each CORBA {@link Column} object.
	*
	* @param columns Will be released.
	*/
	private void releaseColumns(Column[] columns) {
	if (columns == null) {
	return;
	}

	for (Column column : columns) {
	try {
	column.destroy();
	} catch (AoException e) {
	// ignore
	} catch (Exception e) {
	// ignore
	} finally {
	column._release();
	}
	}
	}

	}