package org.apache.lucene.queryParser.standard.processors;
/**
* 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.
*/
import java.util.LinkedList;
import java.util.List;
import org.apache.lucene.queryParser.core.QueryNodeException;
import org.apache.lucene.queryParser.core.nodes.GroupQueryNode;
import org.apache.lucene.queryParser.core.nodes.MatchNoDocsQueryNode;
import org.apache.lucene.queryParser.core.nodes.ModifierQueryNode;
import org.apache.lucene.queryParser.core.nodes.QueryNode;
import org.apache.lucene.queryParser.core.processors.QueryNodeProcessorImpl;
/**
* This processor removes every {@link QueryNode} that is not a leaf and has not
* children. If after processing the entire tree the root node is not a leaf and
* has no children, a {@link MatchNoDocsQueryNode} object is returned. <br/>
* <br/>
* This processor is used at the end of a pipeline to avoid invalid query node
* tree structures like a {@link GroupQueryNode} or {@link ModifierQueryNode}
* with no children. <br/>
*
* @see QueryNode
* @see MatchNoDocsQueryNode
*/
public class RemoveEmptyNonLeafQueryNodeProcessor extends
QueryNodeProcessorImpl {
private LinkedList<QueryNode> childrenBuffer = new LinkedList<QueryNode>();
public RemoveEmptyNonLeafQueryNodeProcessor() {
// empty constructor
}
@Override
public QueryNode process(QueryNode queryTree) throws QueryNodeException {
queryTree = super.process(queryTree);
if (!queryTree.isLeaf()) {
List<QueryNode> children = queryTree.getChildren();
if (children == null || children.size() == 0) {
return new MatchNoDocsQueryNode();
}
}
return queryTree;
}
@Override
protected QueryNode postProcessNode(QueryNode node) throws QueryNodeException {
return node;
}
@Override
protected QueryNode preProcessNode(QueryNode node) throws QueryNodeException {
return node;
}
@Override
protected List<QueryNode> setChildrenOrder(List<QueryNode> children)
throws QueryNodeException {
try {
for (QueryNode child : children) {
if (!child.isLeaf()) {
List<QueryNode> grandChildren = child.getChildren();
if (grandChildren != null && grandChildren.size() > 0) {
this.childrenBuffer.add(child);
}
} else {
this.childrenBuffer.add(child);
}
}
children.clear();
children.addAll(this.childrenBuffer);
} finally {
this.childrenBuffer.clear();
}
return children;
}
}