OaiPmhUtil.java

/**
 *  Copyright 2009, 2010 The Regents of the University of California
 *  Licensed under the Educational Community 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.osedu.org/licenses/ECL-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 ch.entwine.weblounge.bridge.oaipmh;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

/**
 * General purpose functions for OAI-PMH.
 */
public final class OaiPmhUtil {
  private OaiPmhUtil() {
  }

  /**
   * Convert a date into a UTC string of the given granularity.
   */
  public static String toUtc(Date d, Granularity g) {
    if (d != null) {
      switch (g) {
        case SECOND:
          return toUtcSecond(d);
        case DAY:
          return toUtcDay(d);
        default:
          throw new RuntimeException("bug");
      }
    } else {
      return null;
    }
  }

  /**
   * Convert to a UTC date and time string (granularity is "second").
   */
  public static String toUtcSecond(Date d) {
    return newDateTimeFormat().format(d);
  }

  /**
   * Convert to a UTC date string containing only the day (granularity is
   * "day").
   */
  public static String toUtcDay(Date d) {
    return newDateFormat().format(d);
  }

  /**
   * Convert to a date from a UTC string with either day or second granularity.
   * 
   * @throws ParseException
   *           malformed date string
   */
  public static Date fromUtc(String d) throws ParseException {
    try {
      return newDateTimeFormat().parse(d);
    } catch (ParseException e) {
      return newDateFormat().parse(d);
    }
  }

  public static DateFormat newDateTimeFormat() {
    SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
    f.setTimeZone(TimeZone.getTimeZone("UTC"));
    return f;
  }

  public static DateFormat newDateFormat() {
    SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd");
    f.setTimeZone(TimeZone.getTimeZone("UTC"));
    return f;
  }

  private static final String GRANULARITY_DAY = "YYYY-MM-DD";
  private static final String GRANULARITY_SECOND = "YYYY-MM-DDThh:mm:ssZ";

  /**
   * Convert from a OAI representation. See the <a
   * href="http://www.openarchives.org/OAI/openarchivesprotocol.html#Identify"
   * >spec</a> for further details.
   * 
   * @throws IllegalArgumentException
   *           oai is not valid representation
   */
  public static Granularity fromOaiRepresentation(String oai) {
    if (GRANULARITY_DAY.equals(oai))
      return Granularity.DAY;
    if (GRANULARITY_SECOND.equals(oai))
      return Granularity.SECOND;
    throw new IllegalArgumentException(oai + " is not a valid representation");
  }

  public static String toOaiRepresentation(Granularity g) {
    switch (g) {
      case DAY:
        return GRANULARITY_DAY;
      case SECOND:
        return GRANULARITY_SECOND;
      default:
        throw new RuntimeException("bug");
    }
  }
}