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Lucene example source code file (SlopQueryNode.java)

This example Lucene source code file (SlopQueryNode.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

charsequence, charsequence, clonenotsupportedexception, fieldablenode, fieldablenode, float, override, querynode, querynode, querynodeerror, querynodeimpl, slopquerynode, slopquerynode, string

The Lucene SlopQueryNode.java source code

package org.apache.lucene.queryParser.core.nodes;

/**
 * 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 org.apache.lucene.messages.MessageImpl;
import org.apache.lucene.queryParser.core.QueryNodeError;
import org.apache.lucene.queryParser.core.messages.QueryParserMessages;
import org.apache.lucene.queryParser.core.parser.EscapeQuerySyntax;

/**
 * A {@link SlopQueryNode} represents phrase query with a slop.
 * 
 * From Lucene FAQ: Is there a way to use a proximity operator (like near or
 * within) with Lucene? There is a variable called slop that allows you to
 * perform NEAR/WITHIN-like queries. By default, slop is set to 0 so that only
 * exact phrases will match. When using TextParser you can use this syntax to
 * specify the slop: "doug cutting"~2 will find documents that contain
 * "doug cutting" as well as ones that contain "cutting doug".
 */
public class SlopQueryNode extends QueryNodeImpl implements FieldableNode {

  private static final long serialVersionUID = 0L;

  private int value = 0;

  /**
   * @param query
   *          - QueryNode Tree with the phrase
   * @param value
   *          - slop value
   */
  public SlopQueryNode(QueryNode query, int value) {
    if (query == null) {
      throw new QueryNodeError(new MessageImpl(
          QueryParserMessages.NODE_ACTION_NOT_SUPPORTED, "query", "null"));
    }

    this.value = value;
    setLeaf(false);
    allocate();
    add(query);
  }

  public QueryNode getChild() {
    return getChildren().get(0);
  }

  public int getValue() {
    return this.value;
  }

  private CharSequence getValueString() {
    Float f = Float.valueOf(this.value);
    if (f == f.longValue())
      return "" + f.longValue();
    else
      return "" + f;

  }

  @Override
  public String toString() {
    return "<slop value='" + getValueString() + "'>" + "\n"
        + getChild().toString() + "\n</slop>";
  }

  public CharSequence toQueryString(EscapeQuerySyntax escapeSyntaxParser) {
    if (getChild() == null)
      return "";
    return getChild().toQueryString(escapeSyntaxParser) + "~"
        + getValueString();
  }

  @Override
  public QueryNode cloneTree() throws CloneNotSupportedException {
    SlopQueryNode clone = (SlopQueryNode) super.cloneTree();

    clone.value = this.value;

    return clone;
  }

  public CharSequence getField() {
    QueryNode child = getChild();

    if (child instanceof FieldableNode) {
      return ((FieldableNode) child).getField();
    }

    return null;

  }

  public void setField(CharSequence fieldName) {
    QueryNode child = getChild();

    if (child instanceof FieldableNode) {
      ((FieldableNode) child).setField(fieldName);
    }

  }

}

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