MetadataFilter.java

/**
 * Licensed to DigitalPebble Ltd under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * DigitalPebble 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 com.digitalpebble.stormcrawler.filtering.metadata;

import java.net.URL;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.Map.Entry;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.digitalpebble.stormcrawler.Metadata;
import com.digitalpebble.stormcrawler.filtering.URLFilter;
import com.fasterxml.jackson.databind.JsonNode;

/**
 * Filter out URLs based on metadata in the source document
 */
public class MetadataFilter implements URLFilter {

    private static final Logger LOG = LoggerFactory
            .getLogger(MetadataFilter.class);

    private final LinkedList<String[]> mdFilters = new LinkedList<>();

    @Override
    public void configure(Map stormConf, JsonNode paramNode) {
        java.util.Iterator<Entry<String, JsonNode>> iter = paramNode.fields();
        while (iter.hasNext()) {
            Entry<String, JsonNode> entry = iter.next();
            String key = entry.getKey();
            String value = entry.getValue().asText();
            mdFilters.add(new String[] { key, value });
        }
    }

    @Override
    public String filter(URL pageUrl, Metadata sourceMetadata,
            String urlToFilter) {
        if (sourceMetadata == null) {
            return urlToFilter;
        }
        // check whether any of the metadata can be found in the source
        Iterator<String[]> iter = mdFilters.iterator();
        while (iter.hasNext()) {
            String[] kv = iter.next();
            String[] vals = sourceMetadata.getValues(kv[0]);
            if (vals == null) {
                continue;
            }
            for (String v : vals) {
                if (v.equalsIgnoreCase(kv[1])) {
                    LOG.debug("Filtering {} matching metadata {}:{}",
                            urlToFilter, kv[0], kv[1]);
                    return null;
                }
            }
        }
        return urlToFilter;
    }

}