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package oracle.toplink.essentials.queryframework;

import oracle.toplink.essentials.exceptions.*;
import oracle.toplink.essentials.descriptors.DescriptorQueryManager;
import oracle.toplink.essentials.internal.sessions.AbstractRecord;
import oracle.toplink.essentials.internal.sessions.UnitOfWorkImpl;
import oracle.toplink.essentials.internal.sessions.AbstractSession;

/**
 * <p><b>Purpose</b>: Used for deleting objects.
 * <p>
 * <p><b>Responsibilities</b>:
 * Extract primary key from object and delete it.
 *
 * @author Yvon Lavoie
 * @since TOPLink/Java 1.0
 */
public class DeleteObjectQuery extends WriteObjectQuery {
    public DeleteObjectQuery() {
        super();
    }

    public DeleteObjectQuery(Object objectToDelete) {
        this();
        setObject(objectToDelete);
    }

    public DeleteObjectQuery(Call call) {
        this();
        setCall(call);
    }

    /**
     * INTERNAL:
     * Check to see if a custom query should be used for this query.
     * This is done before the query is copied and prepared/executed.
     * null means there is none.
     */
    protected DatabaseQuery checkForCustomQuery(AbstractSession session, AbstractRecord translationRow) {
        checkDescriptor(session);

        // check if user defined a custom query
        DescriptorQueryManager queryManager = getDescriptor().getQueryManager();
        if ((!isCallQuery())// this is not a hand-coded (custom SQL, SDK etc.) call
                 &&(!isUserDefined())// and this is not a user-defined query (in the query manager)
                 &&queryManager.hasDeleteQuery()) {// and there is a user-defined query (in the query manager)
            return queryManager.getDeleteQuery();
        }

        return null;
    }

    /**
     * INTERNAL:
     * Perform a delete.
     */
    public void executeCommit() throws DatabaseException {
        // object will only be null if the transaction is being commited directly from a changeset
        if (getObject() != null) {
            // if the object is not null then it is more effecient to build the row from the
            // object then the changeSet.
            getQueryMechanism().deleteObjectForWrite();
        } else {
            // TODO: Must this case be implemented?
            // has a changeSet so we must use it in the case that there is no object
//            getQueryMechanism().deleteObjectForWriteWithChangeSet();
        }
    }

    /**
     * INTERNAL:
     * Code was moved from UnitOfWork.internalExecuteQuery
     *
     * @param unitOfWork
     * @param translationRow
     * @return
     * @throws oracle.toplink.essentials.exceptions.DatabaseException
     * @throws oracle.toplink.essentials.exceptions.OptimisticLockException
     */
    protected Object executeInUnitOfWorkObjectLevelModifyQuery(UnitOfWorkImpl unitOfWork, AbstractRecord translationRow) throws DatabaseException, OptimisticLockException {
        Object result = unitOfWork.processDeleteObjectQuery(this);
        if (result != null) {
            // if the above method returned something then the unit of work
            //was not writing so the object has been stored to delete later
            //so return the object.  See the above method for the cases
            //where this object will be returned.
            return result;
        }
        return super.executeInUnitOfWorkObjectLevelModifyQuery(unitOfWork, translationRow);
    }

    /**
     * INTERNAL:
     * Perform a shallow delete.
     */
    public void executeShallowWrite() {
        getQueryMechanism().shallowDeleteObjectForWrite(getObject(), this, getSession().getCommitManager());
    }
    
    /**
     * PUBLIC:
     * Return if this is a delete object query.
     */
    public boolean isDeleteObjectQuery() {
        return true;
    }

    /**
     * INTERNAL:
     * Prepare the receiver for execution in a session.
     */
    protected void prepare() {
        super.prepare();

        getQueryMechanism().prepareDeleteObject();
    }

    /**
     * INTERNAL:
     * Set the properties needed to be cascaded into the custom query.
     */
    protected void prepareCustomQuery(DatabaseQuery customQuery) {
        DeleteObjectQuery customDeleteQuery = (DeleteObjectQuery)customQuery;
        customDeleteQuery.setObject(getObject());
        customDeleteQuery.setObjectChangeSet(getObjectChangeSet());
        customDeleteQuery.setCascadePolicy(getCascadePolicy());
        customDeleteQuery.setShouldMaintainCache(shouldMaintainCache());
        customDeleteQuery.setTranslationRow(customDeleteQuery.getDescriptor().getObjectBuilder().buildRow(getObject(), customDeleteQuery.getSession()));
    }

    /**
     * INTERNAL:
     * Prepare the receiver for execution in a session. In particular,
     * verify that the object is not null and contains a valid primary key.
     */
    public void prepareForExecution() throws QueryException {
        super.prepareForExecution();

        // Add the write lock field if required		
        if (getDescriptor().usesOptimisticLocking()) {
            getDescriptor().getOptimisticLockingPolicy().addLockValuesToTranslationRow(this);
        }
    }
}