Lucene example source code file (RegexTermEnum.java)

This example Lucene source code file (RegexTermEnum.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, ioexception, override, override, regexcapabilities, regextermenum, regextermenum, string, string, term

The Lucene RegexTermEnum.java source code

package org.apache.lucene.search.regex;

/**
 * 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.search.FilteredTermEnum;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;

import java.io.IOException;

/**
 * Subclass of FilteredTermEnum for enumerating all terms that match the
 * specified regular expression term using the specified regular expression
 * implementation.
 * <p>
 * Term enumerations are always ordered by Term.compareTo().  Each term in
 * the enumeration is greater than all that precede it.
 */

public class RegexTermEnum extends FilteredTermEnum {
  private String field = "";
  private String pre = "";
  private boolean endEnum = false;
  private RegexCapabilities regexImpl;

  public RegexTermEnum(IndexReader reader, Term term, RegexCapabilities regexImpl) throws IOException {
    super();
    field = term.field();
    String text = term.text();
    this.regexImpl = regexImpl;

    regexImpl.compile(text);

    pre = regexImpl.prefix();
    if (pre == null) pre = "";

    setEnum(reader.terms(new Term(term.field(), pre)));
  }

  @Override
  protected final boolean termCompare(Term term) {
    if (field == term.field()) {
      String searchText = term.text();
      if (searchText.startsWith(pre)) {
        return regexImpl.match(searchText);
      }
    }
    endEnum = true;
    return false;
  }

  @Override
  public final float difference() {
// TODO: adjust difference based on distance of searchTerm.text() and term().text()
    return 1.0f;
  }

  @Override
  public final boolean endEnum() {
    return endEnum;
  }

  @Override
  public void close() throws IOException {
    super.close();
    field = null;
  }
}