urlfilters.java

nutch0.8源码

/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed 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 java.util.HashMap;

import org.apache.nutch.plugin.Extension;
import org.apache.nutch.plugin.ExtensionPoint;
import org.apache.nutch.plugin.PluginRuntimeException;
import org.apache.nutch.plugin.PluginRepository;

import org.apache.hadoop.conf.Configuration;
/** Creates and caches {@link URLFilter} implementing plugins.*/
public class URLFilters {

  private URLFilter[] filters;

  public URLFilters(Configuration conf) {
      String order = conf.get("urlfilter.order");
      this.filters = (URLFilter[]) conf.getObject(URLFilter.class.getName());
      
      if (this.filters == null) {
            String[] orderedFilters = null;
            if (order != null && !order.trim().equals("")) {
                orderedFilters = order.split("\\s+");
            }

            try {
                ExtensionPoint point = PluginRepository.get(conf)
                        .getExtensionPoint(URLFilter.X_POINT_ID);
                if (point == null)
                    throw new RuntimeException(URLFilter.X_POINT_ID
                            + " not found.");
                Extension[] extensions = point.getExtensions();
                HashMap filterMap = new HashMap();
                for (int i = 0; i < extensions.length; i++) {
                    Extension extension = extensions[i];
                    URLFilter filter = (URLFilter) extension
                            .getExtensionInstance();
                    if (!filterMap.containsKey(filter.getClass().getName())) {
                        filterMap.put(filter.getClass().getName(), filter);
                    }
                }
                if (orderedFilters == null) {
                    conf.setObject(URLFilter.class.getName(), filterMap
                            .values().toArray(new URLFilter[0]));
                } else {
                    URLFilter[] filter = new URLFilter[orderedFilters.length];
                    for (int i = 0; i < orderedFilters.length; i++) {
                        filter[i] = (URLFilter) filterMap
                                .get(orderedFilters[i]);
                    }
                    conf.setObject(URLFilter.class.getName(), filter);
                }
            } catch (PluginRuntimeException e) {
                throw new RuntimeException(e);
            }
            this.filters = (URLFilter[]) conf.getObject(URLFilter.class
                    .getName());
        }
  }  

  /** Run all defined filters. Assume logical AND. */
  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;
  }
}