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Lucene example source code file (WildcardQuery.java)

This example Lucene source code file (WildcardQuery.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

filteredtermenum, io, ioexception, multitermquery, override, override, prefixtermenum, string, string, stringbuilder, stringbuilder, term, wildcardquery, wildcardquery, wildcardtermenum

The Lucene WildcardQuery.java source code

package org.apache.lucene.search;

/**
 * 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.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.util.ToStringUtils;

import java.io.IOException;

/** Implements the wildcard search query. Supported wildcards are <code>*, which
 * matches any character sequence (including the empty one), and <code>?,
 * which matches any single character. Note this query can be slow, as it
 * needs to iterate over many terms. In order to prevent extremely slow WildcardQueries,
 * a Wildcard term should not start with one of the wildcards <code>* or
 * <code>?.
 * 
 * <p>This query uses the {@link
 * MultiTermQuery#CONSTANT_SCORE_AUTO_REWRITE_DEFAULT}
 * rewrite method.
 *
 * @see WildcardTermEnum */
public class WildcardQuery extends MultiTermQuery {
  private boolean termContainsWildcard;
  private boolean termIsPrefix;
  protected Term term;
    
  public WildcardQuery(Term term) {
    this.term = term;
    String text = term.text();
    this.termContainsWildcard = (text.indexOf('*') != -1)
        || (text.indexOf('?') != -1);
    this.termIsPrefix = termContainsWildcard 
        && (text.indexOf('?') == -1) 
        && (text.indexOf('*') == text.length() - 1);
  }

  @Override
  protected FilteredTermEnum getEnum(IndexReader reader) throws IOException {
    if (termIsPrefix) {
      return new PrefixTermEnum(reader, term.createTerm(term.text()
          .substring(0, term.text().indexOf('*')))); 
    } else if (termContainsWildcard) {
      return new WildcardTermEnum(reader, getTerm());
    } else {
      return new SingleTermEnum(reader, getTerm());
    }
  }
  
  /**
   * Returns the pattern term.
   */
  public Term getTerm() {
    return term;
  }
  
  /** Prints a user-readable version of this query. */
  @Override
  public String toString(String field) {
    StringBuilder buffer = new StringBuilder();
    if (!term.field().equals(field)) {
      buffer.append(term.field());
      buffer.append(":");
    }
    buffer.append(term.text());
    buffer.append(ToStringUtils.boost(getBoost()));
    return buffer.toString();
  }

  @Override
  public int hashCode() {
    final int prime = 31;
    int result = super.hashCode();
    result = prime * result + ((term == null) ? 0 : term.hashCode());
    return result;
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (!super.equals(obj))
      return false;
    if (getClass() != obj.getClass())
      return false;
    WildcardQuery other = (WildcardQuery) obj;
    if (term == null) {
      if (other.term != null)
        return false;
    } else if (!term.equals(other.term))
      return false;
    return true;
  }

}

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