nutch-1.4中IndexingFilter的变化

nutch-1.4后IndexingFilter扩展点中少了一个用于添加索引Field属性的函数addIndexBackendOptions(Configuration conf)，这样如果再用nutch-1.2中的LuceneWriter做索引，需要自己设置Field的属性，下面代码为nutch-1.4的IndexingFilter类源代码：

/** * 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. */package org.apache.nutch.indexer;// Hadoop importsimport org.apache.hadoop.conf.Configurable;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.io.Text;// Nutch importsimport org.apache.nutch.parse.Parse;import org.apache.nutch.crawl.CrawlDatum;import org.apache.nutch.crawl.Inlinks;import org.apache.nutch.plugin.Pluggable;/** Extension point for indexing.  Permits one to add metadata to the indexed * fields.  All plugins found which implement this extension point are run * sequentially on the parse. */public interface IndexingFilter extends Pluggable, Configurable {  /** The name of the extension point. */  final static String X_POINT_ID = IndexingFilter.class.getName();  /**   * Adds fields or otherwise modifies the document that will be indexed for a   * parse. Unwanted documents can be removed from indexing by returning a null value.   *    * @param doc document instance for collecting fields   * @param parse parse data instance   * @param url page url   * @param datum crawl datum for the page   * @param inlinks page inlinks   * @return modified (or a new) document instance, or null (meaning the document   * should be discarded)   * @throws IndexingException   */  NutchDocument filter(NutchDocument doc, Parse parse, Text url, CrawlDatum datum, Inlinks inlinks)    throws IndexingException;}