org.apache.nutch.api.impl.db.DbIterator.java Source code

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/*******************************************************************************
 * 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.
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package org.apache.nutch.api.impl.db;

import java.io.IOException;
import java.util.Map;
import java.util.Set;

import org.apache.avro.util.Utf8;
import org.apache.commons.collections.CollectionUtils;
import org.apache.gora.query.Result;
import org.apache.nutch.storage.Mark;
import org.apache.nutch.storage.WebPage;
import org.apache.nutch.util.NutchJob;
import org.apache.nutch.util.TableUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.Sets;
import com.google.common.collect.UnmodifiableIterator;

public class DbIterator extends UnmodifiableIterator<Map<String, Object>> {
    private static final Logger LOG = LoggerFactory.getLogger(DbIterator.class);

    private Result<String, WebPage> result;
    private boolean hasNext;
    private String url;
    private WebPage page;
    private Utf8 batchId;
    private Set<String> commonFields;

    DbIterator(Result<String, WebPage> res, Set<String> fields, String batchId) {
        this.result = res;
        if (batchId != null) {
            this.batchId = new Utf8(batchId);
        }
        if (fields != null) {
            this.commonFields = Sets.newTreeSet(fields);
        }
        try {
            skipNonRelevant();
        } catch (Exception e) {
            LOG.error("Cannot create db iterator!", e);
        }
    }

    private void skipNonRelevant() throws Exception, IOException {
        hasNext = result.next();
        if (!hasNext) {
            return;
        }
        if (batchId == null) {
            return;
        }

        while (hasNext) {
            WebPage page = result.get();
            Utf8 mark = Mark.UPDATEDB_MARK.checkMark(page);
            if (NutchJob.shouldProcess(mark, batchId)) {
                return;
            }

            LOG.debug("Skipping {}; different batch id", result.getKey());
            hasNext = result.next();
        }
    }

    public boolean hasNext() {
        return hasNext;
    }

    public Map<String, Object> next() {
        url = result.getKey();
        page = WebPage.newBuilder(result.get()).build();
        try {
            skipNonRelevant();
            if (!hasNext) {
                result.close();
            }
        } catch (Exception e) {
            LOG.error("Cannot get next result!", e);
            hasNext = false;
            return null;
        }
        return pageAsMap(url, page);
    }

    private Map<String, Object> pageAsMap(String url, WebPage page) {
        Map<String, Object> result = DbPageConverter.convertPage(page, commonFields);

        if (CollectionUtils.isEmpty(commonFields) || commonFields.contains("url")) {
            result.put("url", TableUtil.unreverseUrl(url));
        }
        return result;
    }

}