GroupByClauseStateObject.java

/*******************************************************************************
 * Copyright (c) 2011, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation
 *
 ******************************************************************************/
package org.eclipse.persistence.jpa.jpql.tools.model.query;

import java.io.IOException;
import java.util.List;
import org.eclipse.persistence.jpa.jpql.parser.GroupByClause;
import org.eclipse.persistence.jpa.jpql.parser.GroupByItemBNF;
import static org.eclipse.persistence.jpa.jpql.parser.AbstractExpression.*;
import static org.eclipse.persistence.jpa.jpql.parser.Expression.*;

/**
 * The <code><b>GROUP BY</b></code> construct enables the aggregation of values according to the
 * properties of an entity class.
 *
 * <div><b>BNF:</b> <code>groupby_clause ::= GROUP BY groupby_item {, groupby_item}*</code><p></div>
 *
 * @see GroupByClause
 *
 * @version 2.4
 * @since 2.4
 * @author Pascal Filion
 */
@SuppressWarnings({"nls", "unused"}) // unused used for the import statement: see bug 330740
public class GroupByClauseStateObject extends AbstractListHolderStateObject<StateObject> {

    /**
     * Notify the list of {@link StateObject StateObjects} representing the <code><b>GROUP BY</b></code>
     * items.
     */
    public static final String GROUP_BY_ITEMS_LIST = "groupByItems";

    /**
     * Creates a new <code>GroupByClauseStateObject</code>.
     *
     * @param parent The parent of this state object, which cannot be <code>null</code>
     * @exception NullPointerException The given parent cannot be <code>null</code>
     */
    public GroupByClauseStateObject(AbstractSelectStatementStateObject parent) {
        super(parent);
    }

    /**
     * {@inheritDoc}
     */
    public void accept(StateObjectVisitor visitor) {
        visitor.visit(this);
    }

    /**
     * Adds the given path as a select item, which can either be an identification variable or a
     * state-field path expression.
     *
     * @param path Either an identification variable or a state-field path expression
     * @return The {@link StateObject} encapsulating the given path
     */
    public StateObject addGroupByItem(String path) {
        StateObject stateObject = buildStateObject(path, GroupByItemBNF.ID);
        addItem(stateObject);
        return stateObject;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public GroupByClause getExpression() {
        return (GroupByClause) super.getExpression();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public AbstractSelectStatementStateObject getParent() {
        return (AbstractSelectStatementStateObject) super.getParent();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isEquivalent(StateObject stateObject) {
        return super.isEquivalent(stateObject) &&
               areChildrenEquivalent((GroupByClauseStateObject) stateObject);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected String listName() {
        return GROUP_BY_ITEMS_LIST;
    }

    /**
     * Parses the given JPQL fragment, which will represent the group by items. The fragment cannot
     * start with the <code><b>GROUP BY</b></code>.
     *
     * @param jpqlFragment The string representation of the group by items
     */
    public void parse(String jpqlFragment) {
        List<StateObject> stateObjects = buildStateObjects(jpqlFragment, GroupByItemBNF.ID);
        addItems(stateObjects);
    }

    /**
     * Keeps a reference of the {@link GroupByClause parsed object} object, which should only be
     * done when this object is instantiated during the conversion of a parsed JPQL query into
     * {@link StateObject StateObjects}.
     *
     * @param expression The {@link GroupByClause parsed object} representing a <code><b>GROUP
     * BY</b></code> clause
     */
    public void setExpression(GroupByClause expression) {
        super.setExpression(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void toTextInternal(Appendable writer) throws IOException {
        writer.append(GROUP_BY);
        if (hasItems()) {
            writer.append(SPACE);
            toStringItems(writer, true);
        }
    }
}