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Lucene example source code file (QueryParserUtil.java)

This example Lucene source code file (QueryParserUtil.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

analyzer, booleanquery, booleanquery, illegalargumentexception, query, query, querynodeexception, queryparserutil, standardqueryparser, standardqueryparser, string, string, stringbuilder

The Lucene QueryParserUtil.java source code

package org.apache.lucene.queryParser.standard;

/**
 * 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.analysis.Analyzer;
import org.apache.lucene.queryParser.core.QueryNodeException;
import org.apache.lucene.search.BooleanClause;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.Query;

/**
 * This class defines utility methods to (help) parse query strings into
 * {@link Query} objects.
 */
final public class QueryParserUtil {

  /**
   * Parses a query which searches on the fields specified.
   * <p>
   * If x fields are specified, this effectively constructs:
   * 
   * <pre>
   * <code>
   * (field1:query1) (field2:query2) (field3:query3)...(fieldx:queryx)
   * </code>
   * </pre>
   * 
   * @param queries
   *          Queries strings to parse
   * @param fields
   *          Fields to search on
   * @param analyzer
   *          Analyzer to use
   * @throws IllegalArgumentException
   *           if the length of the queries array differs from the length of the
   *           fields array
   */
  public static Query parse(String[] queries, String[] fields, Analyzer analyzer)
      throws QueryNodeException {
    if (queries.length != fields.length)
      throw new IllegalArgumentException("queries.length != fields.length");
    BooleanQuery bQuery = new BooleanQuery();

    StandardQueryParser qp = new StandardQueryParser();
    qp.setAnalyzer(analyzer);

    for (int i = 0; i < fields.length; i++) {
      Query q = qp.parse(queries[i], fields[i]);

      if (q != null && // q never null, just being defensive
          (!(q instanceof BooleanQuery) || ((BooleanQuery) q).getClauses().length > 0)) {
        bQuery.add(q, BooleanClause.Occur.SHOULD);
      }
    }
    return bQuery;
  }

  /**
   * Parses a query, searching on the fields specified. Use this if you need to
   * specify certain fields as required, and others as prohibited.
   * <p>
   * 
   * <pre>
   * Usage:
   * <code>
   * String[] fields = {"filename", "contents", "description"};
   * BooleanClause.Occur[] flags = {BooleanClause.Occur.SHOULD,
   *                BooleanClause.Occur.MUST,
   *                BooleanClause.Occur.MUST_NOT};
   * MultiFieldQueryParser.parse("query", fields, flags, analyzer);
   * </code>
   * </pre>
   *<p>
   * The code above would construct a query:
   * 
   * <pre>
   * <code>
   * (filename:query) +(contents:query) -(description:query)
   * </code>
   * </pre>
   * 
   * @param query
   *          Query string to parse
   * @param fields
   *          Fields to search on
   * @param flags
   *          Flags describing the fields
   * @param analyzer
   *          Analyzer to use
   * @throws IllegalArgumentException
   *           if the length of the fields array differs from the length of the
   *           flags array
   */
  public static Query parse(String query, String[] fields,
      BooleanClause.Occur[] flags, Analyzer analyzer) throws QueryNodeException {
    if (fields.length != flags.length)
      throw new IllegalArgumentException("fields.length != flags.length");
    BooleanQuery bQuery = new BooleanQuery();

    StandardQueryParser qp = new StandardQueryParser();
    qp.setAnalyzer(analyzer);

    for (int i = 0; i < fields.length; i++) {
      Query q = qp.parse(query, fields[i]);

      if (q != null && // q never null, just being defensive
          (!(q instanceof BooleanQuery) || ((BooleanQuery) q).getClauses().length > 0)) {
        bQuery.add(q, flags[i]);
      }
    }
    return bQuery;
  }

  /**
   * Parses a query, searching on the fields specified. Use this if you need to
   * specify certain fields as required, and others as prohibited.
   * <p>
   * 
   * <pre>
   * Usage:
   * <code>
   * String[] query = {"query1", "query2", "query3"};
   * String[] fields = {"filename", "contents", "description"};
   * BooleanClause.Occur[] flags = {BooleanClause.Occur.SHOULD,
   *                BooleanClause.Occur.MUST,
   *                BooleanClause.Occur.MUST_NOT};
   * MultiFieldQueryParser.parse(query, fields, flags, analyzer);
   * </code>
   * </pre>
   *<p>
   * The code above would construct a query:
   * 
   * <pre>
   * <code>
   * (filename:query1) +(contents:query2) -(description:query3)
   * </code>
   * </pre>
   * 
   * @param queries
   *          Queries string to parse
   * @param fields
   *          Fields to search on
   * @param flags
   *          Flags describing the fields
   * @param analyzer
   *          Analyzer to use
   * @throws IllegalArgumentException
   *           if the length of the queries, fields, and flags array differ
   */
  public static Query parse(String[] queries, String[] fields,
      BooleanClause.Occur[] flags, Analyzer analyzer) throws QueryNodeException {
    if (!(queries.length == fields.length && queries.length == flags.length))
      throw new IllegalArgumentException(
          "queries, fields, and flags array have have different length");
    BooleanQuery bQuery = new BooleanQuery();

    StandardQueryParser qp = new StandardQueryParser();
    qp.setAnalyzer(analyzer);

    for (int i = 0; i < fields.length; i++) {
      Query q = qp.parse(queries[i], fields[i]);

      if (q != null && // q never null, just being defensive
          (!(q instanceof BooleanQuery) || ((BooleanQuery) q).getClauses().length > 0)) {
        bQuery.add(q, flags[i]);
      }
    }
    return bQuery;
  }

  /**
   * Returns a String where those characters that TextParser expects to be
   * escaped are escaped by a preceding <code>\.
   */
  public static String escape(String s) {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < s.length(); i++) {
      char c = s.charAt(i);
      // These characters are part of the query syntax and must be escaped
      if (c == '\\' || c == '+' || c == '-' || c == '!' || c == '(' || c == ')'
          || c == ':' || c == '^' || c == '[' || c == ']' || c == '\"'
          || c == '{' || c == '}' || c == '~' || c == '*' || c == '?'
          || c == '|' || c == '&') {
        sb.append('\\');
      }
      sb.append(c);
    }
    return sb.toString();
  }

}

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