/*
* 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<T extends QueryNode> extends QueryNode {
/**
* Empty result.
*/
private static final Object[] EMPTY = new Object[0];
/**
* The list of operands / children
*/
protected List<T> operands = null;
/**
* Creates a new <code>NAryQueryNode</code> with a reference to a parent
* {@link QueryNode}.
*
* @param parent the parent node.
*/
public NAryQueryNode(QueryNode parent) {
super(parent);
}
/**
* Creates a new <code>NAryQueryNode</code> with a reference to a parent
* {@link QueryNode} and initial <code>operands</code>.
*
* @param parent the parent node.
* @param operands child nodes of this <code>NAryQueryNode</code>.
*/
public NAryQueryNode(QueryNode parent, T[] operands) {
super(parent);
if (operands.length > 0) {
this.operands = new ArrayList<T>();
this.operands.addAll(Arrays.asList(operands));
}
}
/**
* Adds a new <code>operand</code> (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<T>();
}
operands.add(operand);
}
/**
* Removes an <code>operand</code> (child node) from this query node.
*
* @param operand the child to remove.
* @return <code>true</code> if the operand was in the list of child nodes
* and has been removed; <code>false</code> if this node does not contain
* <code>operand</code> 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 <code>QueryNode</code> operands of this
* <code>QueryNode</code>. Returns an empty array if no operands are set.
*
* @return currently set <code>QueryNode</code> 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 <code>visitor</code> for all operands
* of this <code>NAryQueryNode</code>.
*
* @param visitor the visitor to call back.
* @param data arbitrary data for the visitor.
* @return the return values of the <code>visitor.visit()</code> calls.
* @throws RepositoryException if an error occurs.
*/
public Object[] acceptOperands(QueryNodeVisitor visitor, Object data) throws RepositoryException {
if (operands == null) {
return EMPTY;
}
List<Object> result = new ArrayList<Object>(operands.size());
for (T operand : operands) {
Object r = operand.accept(visitor, data);
if (r != null) {
result.add(r);
}
}
return result.toArray();
}
/**
* {@inheritDoc}
*/
public boolean equals(Object obj) {
if (obj instanceof NAryQueryNode) {
NAryQueryNode other = (NAryQueryNode) obj;
return operands == null ? other.operands == null : operands.equals(other.operands);
}
return false;
}
/**
* {@inheritDoc}
*/
public boolean needsSystemTree() {
if (operands == null) {
return false;
}
for (T operand : operands) {
if (operand.needsSystemTree()) {
return true;
}
}
return false;
}
}