org.apache.jackrabbit.spi.commons.query.NAryQueryNode Maven / Gradle / Ivy

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.jackrabbit.spi.commons.query;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import javax.jcr.RepositoryException;

/**
 * Defines an abstract query node for nodes that have child nodes.
 */
public abstract class NAryQueryNode extends QueryNode {

    /**
     * Empty result.
     */
    private static final Object[] EMPTY = new Object[0];

    /**
     * The list of operands / children
     */
    protected List operands = null;

    /**
     * Creates a new NAryQueryNode with a reference to a parent
     * {@link QueryNode}.
     *
     * @param parent the parent node.
     */
    public NAryQueryNode(QueryNode parent) {
        super(parent);
    }

    /**
     * Creates a new NAryQueryNode with a reference to a parent
     * {@link QueryNode} and initial operands.
     *
     * @param parent   the parent node.
     * @param operands child nodes of this NAryQueryNode.
     */
    public NAryQueryNode(QueryNode parent, T[] operands) {
        super(parent);
        if (operands.length > 0) {
            this.operands = new ArrayList();
            this.operands.addAll(Arrays.asList(operands));
        }
    }

    /**
     * Adds a new operand (child node) to this query node.
     *
     * @param operand the child {@link QueryNode} to add.
     */
    public void addOperand(T operand) {
        if (operands == null) {
            operands = new ArrayList();
        }
        operands.add(operand);
    }

    /**
     * Removes an operand (child node) from this query node.
     *
     * @param operand the child to remove.
     * @return true if the operand was in the list of child nodes
     *  and has been removed; false if this node does not contain
     *  operand as a child node.
     */
    public boolean removeOperand(T operand) {
        if (operands == null) {
            return false;
        }
        // JCR-1650 search the operand without relying on Object#equals(Object)
        Iterator it = operands.iterator();
        while (it.hasNext()) {
            if (it.next() == operand) {
                it.remove();
                return true;
            }
        }
        return false;
    }

    /**
     * Returns an array of currently set QueryNode operands of this
     * QueryNode. Returns an empty array if no operands are set.
     *
     * @return currently set QueryNode operands.
     */
    public QueryNode[] getOperands() {
        if (operands == null) {
            return new QueryNode[0];
        } else {
            return operands.toArray(new QueryNode[operands.size()]);
        }
    }

    /**
     * Returns the number of operands.
     * @return the number of operands.
     */
    public int getNumOperands() {
        if (operands == null) {
            return 0;
        } else {
            return operands.size();
        }
    }

    /**
     * Helper class to accept a visitor for all operands
     * of this NAryQueryNode.
     *
     * @param visitor the visitor to call back.
     * @param data    arbitrary data for the visitor.
     * @return the return values of the visitor.visit() calls.
     * @throws RepositoryException if an error occurs.
     */
    public Object[] acceptOperands(QueryNodeVisitor visitor, Object data) throws RepositoryException {
        if (operands == null) {
            return EMPTY;
        }

        List