src/java/org/apache/nutch/net/URLFilters.java

/*
 * 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.net;

import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.plugin.PluginRepository;

/**
 * Creates and caches plugins implementing {@link URLFilter}. Filters URLs using
 * the active filters defined by the properties "plugin.includes",
 * "plugin.excludes" and "urlfilter.order".
 */
public class URLFilters {

  public static final String URLFILTER_ORDER = "urlfilter.order";
  private URLFilter[] filters;

  public URLFilters(Configuration conf) {
    this.filters = (URLFilter[]) PluginRepository.get(conf).getOrderedPlugins(
        URLFilter.class, URLFilter.X_POINT_ID, URLFILTER_ORDER);
  }

  public URLFilter[] getFilters() {
    return this.filters;
  }

  /**
   * Run all defined filters. Assume logical AND. To control performance, the
   * ULFilter classes can be ordered by the property "urlfilter.order".
   * 
   * @param urlString
   *          to execute filters on
   * @return filtered result
   * @throws URLFilterException
   *           if there is an issue executing any URLFilter implementations.
   */
  public String filter(String urlString) throws URLFilterException {
    for (int i = 0; i < this.filters.length; i++) {
      if (urlString == null)
        return null;
      urlString = this.filters[i].filter(urlString);

    }
    return urlString;
  }
}