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This article introduces the relevant knowledge of "how to use Storm IPResolutionBolt to write crawlers". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Package com.digitalpebble.storm.crawler.bolt;import java.net.InetAddress;import java.net.MalformedURLException;import java.net.URL;import java.util.HashMap;import java.util.Map;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import backtype.storm.task.OutputCollector;import backtype.storm.task.TopologyContext;import backtype.storm.topology.OutputFieldsDeclarer;import backtype.storm.topology.base.BaseRichBolt;import backtype.storm.tuple.Fields;import backtype.storm.tuple.Tuple;import backtype.storm.tuple.Values Public class IPResolutionBolt extends BaseRichBolt {public static final Logger LOG = LoggerFactory .getLogger (IPResolutionBolt.class); OutputCollector _ collector; @ SuppressWarnings ("unchecked") public void execute (Tuple tuple) {String url = tuple.getStringByField ("url"); HashMap metadata = null / / determine here whether our tuple contains Meradata if (tuple.contains ("metadata")) metadata = (HashMap) tuple .getValueByField ("metadata") / / the Metadata here is a HashMap and holds a combination of objects String ip = null; String host = ""; URL u; try {u = new URL (url) Host = u.getHost ();} catch (MalformedURLException E1) {LOG.warn ("Invalid URL:" + url); / / ack it so that it doesn't get replayed _ collector.ack (tuple); return } try {long start = System.currentTimeMillis (); final InetAddress addr = InetAddress.getByName (host); ip = addr.getHostAddress (); long end = System.currentTimeMillis () LOG.info ("IP for:" + host + ">" + ip + "in" + (end-start) + "msec") / / here we launch url,ip,metadata and do an Ack _ collector.emit (tuple, new Values (url,ip,metadata)) for tuple; _ collector.ack (tuple) } catch (final Exception e) {LOG.warn ("Unable to resolve IP for:" + host); _ collector.fail (tuple);}} public void declareOutputFields (OutputFieldsDeclarer declarer) {declarer.declare (new Fields ("url", "ip", "metadata")) } public void prepare (Map stormConf, TopologyContext context, OutputCollector collector) {_ collector = collector;}}

Here we need to note that when declareOutputFields sets our Tuple records object, it is passed "url", "ip", "metadata", not an encapsulated object.

Once we pass a large number of records. Then please make sure that the value passed is set to the object. And get it in the way of the recipient, getValues (0).

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