core/org.eclipse.smila.datamodel/code/src/org/eclipse/smila/datamodel/ValueFormatHelper.java

/**********************************************************************************************
 * Copyright (c) 2008 empolis GmbH and brox IT Solutions GmbH. 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    Juergen Schumacher (empolis GmbH) - initial API and implementation
 *    Andreas Weber (Attensity Europe GmbH) - renamed LiteralFormatHelper -> ValueFormatHelper
 **********************************************************************************************/

package org.eclipse.smila.datamodel;

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

/**
 * helper class for formatting and parsing Values. all methods synchronize on the used local formatter object, so you
 * can use the shared instance. Using multiple instances may improve performance, though, because of less
 * synchronization.
 * 
 * @author jschumacher
 * 
 */
public class ValueFormatHelper {
  /**
   * shared global helper instance.
   */
  public static final ValueFormatHelper INSTANCE = new ValueFormatHelper();

  /** The max. length of strings to be parsed as date. */
  private static final int DATE_LENGTH = 10;

  /** The max. length of strings to be parsed as date time. */
  private static final int DATE_TIME_LENGTH = 24;

  /**
   * formatter to create and parse standard string representations of Date values: "yyyy-MM-dd".
   */
  private final DateFormat _formatDate = new SimpleDateFormat("yyyy-MM-dd");

  /**
   * formatter to create and parse standard string representations of DateTime values: "yyyy-MM-dd'T'HH:mm:ssZ".
   */
  private final DateFormat _formatDateTime = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ");

  /**
   * create local instance.
   */
  public ValueFormatHelper() {
    // nothing to do
  }

  /**
   * format value as Date string.
   * 
   * @param value
   *          a date value
   * @return formatted date.
   */
  public String formatDate(final Date value) {
    synchronized (_formatDate) {
      return _formatDate.format(value);
    }
  }

  /**
   * format value as DateTime string.
   * 
   * @param value
   *          a datetime value
   * @return formatted datetime string
   */
  public String formatDateTime(final Date value) {
    synchronized (_formatDateTime) {
      return _formatDateTime.format(value);
    }
  }

  /**
   * parse a date string.
   * 
   * @param dateString
   *          a date string
   * @return parsed Date
   * @throws ParseException
   *           string has wrong format
   */
  public Date parseDate(final String dateString) throws ParseException {
    if (dateString.length() == DATE_LENGTH) {
      synchronized (_formatDate) {
        return _formatDate.parse(dateString);
      }
    } else {
      throw new ParseException("Length of date string '" + dateString + "' exceeds maximum date length of "
        + DATE_LENGTH, DATE_LENGTH);
    }
  }

  /**
   * parse datetime string.
   * 
   * @param dateTimeString
   *          a datetime string
   * @return parsed Date
   * @throws ParseException
   *           string has wrong format
   */
  public Date parseDateTime(final String dateTimeString) throws ParseException {
    if (dateTimeString.length() == DATE_TIME_LENGTH) {
      synchronized (_formatDateTime) {
        return _formatDateTime.parse(dateTimeString);
      }
    } else {
      throw new ParseException("Length of datetime string '" + dateTimeString + "' exceeds maximum date length of "
        + DATE_TIME_LENGTH, DATE_TIME_LENGTH);
    }
  }

  /**
   * try to parse the string as a date or datetime value. if it doesn't match, create a string value.
   * 
   * @param possibleDateTime
   *          a string to check for date or datetime format.
   * @param f
   *          data factory to use to create the value
   * @return if the string is in datetime format: a datetime value. if the string is in date format: a date value. Else:
   *         a string value.
   */
  public Value tryDateTimeFormats(final String possibleDateTime, final DataFactory f) {
    try {
      switch (possibleDateTime.length()) {
        case DATE_LENGTH:
          Date date;
          synchronized (_formatDate) {
            date = _formatDate.parse(possibleDateTime);
          }
          return f.createDateValue(date);
        case DATE_TIME_LENGTH:
          Date dateTime;
          synchronized (_formatDate) {
            dateTime = _formatDateTime.parse(possibleDateTime);
          }
          return f.createDateTimeValue(dateTime);
        default:
          break;
      }
    } catch (final ParseException ex) {
      ; // Ok, then fallback to string
    }
    return f.createStringValue(possibleDateTime);
  }

}