CachingParser.java

package ua_parser;

import java.util.Map;

import org.apache.commons.collections4.map.LRUMap;

/**
 * When doing webanalytics (with for example PIG) the main pattern is to process
 * weblogs in clickstreams. A basic fact about common clickstreams is that in
 * general the same browser will do multiple requests in sequence. This has the
 * effect that the same useragent will appear in the logfiles and we will see
 * the need to parse the same useragent over and over again.
 *
 * This class introduces a very simple LRU cache to reduce the number of times
 * the parsing is actually done. The default cache size is 1000 and can be
 * configured as object creation.
 *
 * Note: The object handles one cache per parsing method - be carefull when using big sizes.
 *
 * @author Niels Basjes
 *
 */
public class CachingParser extends Parser {

  private static final String    INVALID_CACHE_SIZE_ERROR_MESSAGE = "Invalid cache size provided - Should be greater than 0";

  private int                    cacheSize     = 1000;

  private Map<String, Client>    cacheClient    = null;
  private Map<String, UserAgent> cacheUserAgent = null;
  private Map<String, Device>    cacheDevice    = null;
  private Map<String, OS>        cacheOS        = null;

  // ------------------------------------------

  public CachingParser() {
    super();
  }

  public CachingParser(int cacheSize) {
    super();
    assert cacheSize > 0: INVALID_CACHE_SIZE_ERROR_MESSAGE;
    this.cacheSize = cacheSize;
  }

  // ------------------------------------------

  @Override
  public Client parse(String agentString) {
    if (agentString == null) {
      return null;
    }
    if (cacheClient == null) {
      cacheClient = new LRUMap<>(cacheSize);
    }
    Client client = cacheClient.get(agentString);
    if (client != null) {
      return client;
    }
    client = super.parse(agentString);
    cacheClient.put(agentString, client);
    return client;
  }

  // ------------------------------------------

  @Override
  public UserAgent parseUserAgent(String agentString) {
    if (agentString == null) {
      return null;
    }
    if (cacheUserAgent == null) {
      cacheUserAgent = new LRUMap<>(cacheSize);
    }
    UserAgent userAgent = cacheUserAgent.get(agentString);
    if (userAgent != null) {
      return userAgent;
    }
    userAgent = super.parseUserAgent(agentString);
    cacheUserAgent.put(agentString, userAgent);
    return userAgent;
  }

  // ------------------------------------------

  @Override
  public Device parseDevice(String agentString) {
    if (agentString == null) {
      return null;
    }
    if (cacheDevice == null) {
      cacheDevice = new LRUMap<>(cacheSize);
    }
    Device device = cacheDevice.get(agentString);
    if (device != null) {
      return device;
    }
    device = super.parseDevice(agentString);
    cacheDevice.put(agentString, device);
    return device;
  }

  // ------------------------------------------

  @Override
  public OS parseOS(String agentString) {
    if (agentString == null) {
      return null;
    }

    if (cacheOS == null) {
      cacheOS = new LRUMap<>(cacheSize);
    }
    OS os = cacheOS.get(agentString);
    if (os != null) {
      return os;
    }
    os = super.parseOS(agentString);
    cacheOS.put(agentString, os);
    return os;
  }

  // ------------------------------------------

}