org.eclipse.osbp.jpa.services/src/org/eclipse/osbp/jpa/services/history/HistorizedQueryRedirector.java

package org.eclipse.osbp.jpa.services.history;

import java.util.Calendar;
import java.util.Date;

import org.eclipse.persistence.expressions.Expression;
import org.eclipse.persistence.expressions.ExpressionBuilder;
import org.eclipse.persistence.internal.sessions.AbstractRecord;
import org.eclipse.persistence.internal.sessions.AbstractSession;
import org.eclipse.persistence.internal.sessions.EmptyRecord;
import org.eclipse.persistence.internal.sessions.UnitOfWorkImpl;
import org.eclipse.persistence.queries.DatabaseQuery;
import org.eclipse.persistence.queries.InsertObjectQuery;
import org.eclipse.persistence.queries.QueryRedirector;
import org.eclipse.persistence.queries.ReadObjectQuery;
import org.eclipse.persistence.queries.UpdateObjectQuery;
import org.eclipse.persistence.queries.WriteObjectQuery;
import org.eclipse.persistence.sessions.Record;
import org.eclipse.persistence.sessions.Session;

/**
 * Manages the versioning of historized and timedependent entities.
 */
@SuppressWarnings("serial")
public class HistorizedQueryRedirector implements QueryRedirector {

	@Override
	public Object invokeQuery(DatabaseQuery query, Record arguments, Session session) {
		WriteObjectQuery writeObjectQuery = (WriteObjectQuery) query;

		Object persistedObj = writeObjectQuery.getObject();

		// the object that was persisted / merged
		//
		HistorizedObjectWrapper persistedObjWrapper = new HistorizedObjectWrapper(writeObjectQuery.getDescriptor(),
				persistedObj);

		if (persistedObjWrapper.getVersion() > 1) {
			throw new IllegalArgumentException(
					"Version must be 0. Changing historized records is not allowed: " + persistedObj.toString());
		}
		Object current = getCurrent(persistedObjWrapper, (AbstractSession) session);

		if (current == null) {
			persistedObjWrapper.setId_ValidFrom(createNow(persistedObjWrapper));
			persistedObjWrapper.setValidUntil(getMaxDate());
			persistedObjWrapper.setCurrentHist(true);

			writeObjectQuery.setDoNotRedirect(true);
			Object newAdr = writeObjectQuery.execute((AbstractSession) session, (AbstractRecord) arguments);
			return newAdr;
		} else {

			// sleep 1ms for minimum time intervall between historized records
			try {
				Thread.sleep(1);
			} catch (InterruptedException e) {
			}

			// update the address to be historized
			long now = createNow(persistedObjWrapper);
			Object histCurrentObj = getCurrentManaged(
					new HistorizedObjectWrapper(writeObjectQuery.getDescriptor(), current), (AbstractSession) session);

			// the current object in database with flag histCurrent = true
			//
			HistorizedObjectWrapper histCurrentObjWrapper = new HistorizedObjectWrapper(
					writeObjectQuery.getDescriptor(), histCurrentObj);

			if (query.getDescriptor().getObjectBuilder().compareObjects(persistedObj, histCurrentObj,
					(AbstractSession) session)) {
				return persistedObj;
			}

			histCurrentObjWrapper.setCurrentHist(false);
			histCurrentObjWrapper.setValidUntil(now);
			UpdateObjectQuery updateCurrent = new UpdateObjectQuery(histCurrentObj);
			updateCurrent.setDoNotRedirect(true);
			updateCurrent.setIsUserDefined(true);
			updateCurrent.execute((AbstractSession) session, (AbstractRecord) arguments);

			persistedObjWrapper.setId_ValidFrom(now);
			persistedObjWrapper.setValidUntil(getMaxDate());
			persistedObjWrapper.setCurrentHist(true);
			persistedObjWrapper.setVersion((int) 0);

			InsertObjectQuery insertObjectQ = new InsertObjectQuery(persistedObj);
			insertObjectQ.setIsUserDefined(true);
			insertObjectQ.setDoNotRedirect(true);

			Object newAdr = insertObjectQ.execute((AbstractSession) session, (AbstractRecord) arguments);
			return newAdr;
		}

	}

	private long createNow(HistorizedObjectWrapper wrapper) {
		if (wrapper.isCustomVersion()) {
			return wrapper.getId_ValidFrom();
		}
		return new Date().getTime();
	}

	private Object getCurrent(HistorizedObjectWrapper wrapper, AbstractSession session) {

		UnitOfWorkImpl uow = session.acquireNonSynchronizedUnitOfWork();

		ReadObjectQuery rq = new ReadObjectQuery(wrapper.getEntityClass());

		ExpressionBuilder eb = rq.getExpressionBuilder();
		Expression exp = eb.get(wrapper.getIdAttName()).get(wrapper.getId_IdAttName()).equal(wrapper.getID().id)
				.and(eb.get(wrapper.getCurrentHistAttName()).equal(true));
		rq.setSelectionCriteria(exp);
		rq.dontCheckCache();
		rq.dontMaintainCache();

		Object current = (Object) rq.executeInUnitOfWork(uow, EmptyRecord.getEmptyRecord());

		uow.clearForClose(true);
		return current;
	}

	private Object getCurrentManaged(HistorizedObjectWrapper wrapper, AbstractSession session) {

		ReadObjectQuery rq = new ReadObjectQuery(wrapper.getEntityClass());

		ExpressionBuilder eb = rq.getExpressionBuilder();
		Expression exp = eb.get(wrapper.getIdAttName()).equal(wrapper.getID());
		rq.setSelectionCriteria(exp);

		Object current = rq.execute(session, EmptyRecord.getEmptyRecord());

		return current;
	}

	private long getMaxDate() {
		Calendar cal = Calendar.getInstance();
		cal.set(2099, Calendar.DECEMBER, 31, 0, 0, 0);
		cal.set(Calendar.MILLISECOND, 0);
		Date maxDate = cal.getTime();
		return maxDate.getTime();
	}

}