DateRecord


1   /*********************************************************************
2   *
3   *      Copyright (C) 2001 Andrew Khan
4   *
5   * This library is free software; you can redistribute it and/or
6   * modify it under the terms of the GNU Lesser General Public
7   * License as published by the Free Software Foundation; either
8   * version 2.1 of the License, or (at your option) any later version.
9   *
10  * This library is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13  * Lesser General Public License for more details.
14  *
15  * You should have received a copy of the GNU Lesser General Public
16  * License along with this library; if not, write to the Free Software
17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18  ***************************************************************************/
19  
20  package jxl.write.biff;
21  
22  import java.util.Date  ;
23  import java.util.Calendar  ;
24  import java.util.TimeZone  ;
25  import java.text.DateFormat  ;
26  
27  import jxl.format.CellFormat;
28  import jxl.CellType;
29  import jxl.DateCell;
30  import jxl.biff.Type;
31  import jxl.biff.DoubleHelper;
32  import jxl.write.DateFormats;
33  import jxl.write.WritableCellFormat;
34  
35  /**
36   * A date stored in the database
37   */
38  public abstract class DateRecord extends CellValue
39  {
40    /**
41     * The excel value of the date
42     */
43    private double value;
44    /**
45     * The java representation of the date
46     */
47    private Date   date;
48  
49    /**
50     * Indicates whether this is a full date, or just a time only
51     */
52    private boolean time;
53  
54    // The number of days between 01 Jan 1900 and 01 Jan 1970 - this gives
55    // the UTC offset
56    /**
57     */
58    private final static int utcOffsetDays = 25569;
59  
60    // The number of milliseconds in  a day
61    /**
62     */
63    private final static long msInADay = 24 * 60 * 60 * 1000;
64  
65    /**
66     * This is package protected so that the worksheet might detect
67     * whether or not to override it with the column cell format
68     */
69    static final WritableCellFormat defaultDateFormat = 
70      new WritableCellFormat(DateFormats.DEFAULT);
71  
72    // The number of days between 1 Jan 1900 and 1 March 1900. Excel thinks
73    // the day before this was 29th Feb 1900, but it was 28th Feb 19000.
74    // I guess the programmers thought nobody would notice that they
75    // couldn't be bothered to program this dating anomaly properly
76    /**
77     */
78    private final static int nonLeapDay = 61;
79  
80    /**
81     * Class definition for a dummy variable
82     */
83    protected static final class GMTDate
84    {
85      public GMTDate(){}
86    };
87  
88    /**
89     * Constructor invoked by the user API
90     * 
91     * @param c the column
92     * @param r the row
93     * @param d the date
94     */
95    protected DateRecord(int c, int r, Date   d)
96    {
97      this(c, r, d, defaultDateFormat, true);
98    }
99  
100   /**
101    * Constructor invoked by the user API
102    * 
103    * @param c the column
104    * @param r the row
105    * @param d the date
106    * @param a adjust timezone
107    */
108   protected DateRecord(int c, int r, Date   d, GMTDate a)
109   {
110     this(c, r, d, defaultDateFormat, false);
111   }
112 
113   /**
114    * Constructor invoked from the user API
115    * 
116    * @param c the column
117    * @param r the row
118    * @param st the format for the date
119    * @param d the date
120    */
121   protected DateRecord(int c, int r, Date   d, CellFormat st)
122   {
123     super(Type.NUMBER, c, r,st);
124     date = d;
125     calculateValue(true);
126   }
127 
128   /**
129    * Constructor invoked from the user API
130    * 
131    * @param c the column
132    * @param r the row
133    * @param st the format for the date
134    * @param d the date
135    * @param a adjust for the timezone
136    */
137   protected DateRecord(int c, int r, Date   d, CellFormat st, GMTDate a)
138   {
139     super(Type.NUMBER, c, r, st);
140     date = d;
141     calculateValue(false);
142   }
143 
144   /**
145    * Constructor invoked from the API
146    * 
147    * @param c the column
148    * @param r the row
149    * @param st the date format
150    * @param tim time indicator
151    * @param d the date
152    */
153   protected DateRecord(int c, int r, Date   d, CellFormat st, boolean tim)
154   {
155     super(Type.NUMBER, c, r, st);
156     date = d;
157     calculateValue(false);
158     time = tim;
159   }
160 
161   /**
162    * Constructor invoked when copying a readable spreadsheet
163    * 
164    * @param dc the date to copy
165    */
166   protected DateRecord(DateCell dc)
167   {
168     super(Type.NUMBER, dc);
169     date = dc.getDate();
170     calculateValue(false);
171   }
172 
173   /**
174    * Copy constructor
175    * 
176    * @param c the column
177    * @param r the row
178    * @param dr the record to copy
179    */
180   protected DateRecord(int c, int r, DateRecord dr)
181   {
182     super(Type.NUMBER, c, r, dr);
183     value = dr.value;
184     time = dr.time;
185     date = dr.date;
186   }
187 
188   /**
189    * Calculates the 1900 based numerical value based upon the utc value held
190    * in the date object
191    *
192    * @param adjust TRUE if we want to incorporate timezone information
193    * into the raw UTC date eg. when copying from a spreadsheet
194    */
195   private void calculateValue(boolean adjust)
196   {
197     // Offsets for current time zone
198     long zoneOffset = 0;
199     long dstOffset = 0;
200 
201     // Get the timezone and dst offsets if we want to take these into
202     // account
203     if (adjust)
204     {
205       // Get the current calender, replete with timezone information
206       Calendar   cal = Calendar.getInstance();
207       cal.setTime(date);
208 
209       zoneOffset = cal.get(Calendar.ZONE_OFFSET);
210       dstOffset = cal.get(Calendar.DST_OFFSET);
211     }
212 
213     long utcValue = date.getTime() + zoneOffset + dstOffset;
214 
215     // Convert this to the number of days, plus fractions of a day since
216     // 01 Jan 1970
217     double utcDays = (double) utcValue / (double) msInADay;
218 
219     // Add in the offset to get the number of days since 01 Jan 1900
220     value = utcDays + utcOffsetDays;
221 
222     // Work round a bug in excel.  Excel seems to think there is a date 
223     // called the 29th Feb, 1900 - but this was not a leap year.  
224     // Therefore for values less than 61, we must subtract 1
225     if (value < nonLeapDay)
226     {
227       value -= 1;
228     }
229 
230     // If this refers to a time, then get rid of the integer part
231     if (time)
232     {
233       value = value - (int) value;
234     }
235   }
236 
237   /**
238    * Returns the content type of this cell
239    * 
240    * @return the content type for this cell
241    */
242   public CellType getType()
243   {
244     return CellType.DATE;
245   }
246 
247   /**
248    * Gets the binary data for writing
249    * 
250    * @return the binary data
251    */
252   public byte[] getData()
253   {
254     byte[] celldata = super.getData();
255     byte[] data = new byte[celldata.length + 8];
256     System.arraycopy(celldata, 0, data, 0, celldata.length);
257     DoubleHelper.getIEEEBytes(value, data, celldata.length);
258 
259     return data;
260   }
261 
262   /**
263    * Quick and dirty function to return the contents of this cell as a string.
264    * For more complex manipulation of the contents, it is necessary to cast
265    * this interface to correct subinterface
266    * 
267    * @return the contents of this cell as a string
268    */
269   public String   getContents()
270   {
271     return date.toString();
272   }
273 
274   /**
275    * Sets the date in this cell
276    * 
277    * @param d the date
278    */
279   protected void setDate(Date   d)
280   {
281     date = d;
282     calculateValue(true);
283   }
284 
285   /**
286    * Sets the date in this cell, taking the timezone into account
287    * 
288    * @param d the date
289    * @param a adjust for timezone
290    */
291   protected void setDate(Date   d, GMTDate a)
292   {
293     date = d;
294     calculateValue(false);
295   }
296 
297 
298   /**
299    * Gets the date contained in this cell
300    * 
301    * @return the cell contents
302    */
303   public Date   getDate()
304   {
305     return date;
306   }
307 
308   /**
309    * Indicates whether the date value contained in this cell refers to a date,
310    * or merely a time.  When writing a cell, all dates are fully defined,
311    * even if they refer to a time
312    * 
313    * @return FALSE if this is full date, TRUE if a time
314    */
315   public boolean isTime()
316   {
317     return time;
318   }
319 
320   /**
321    * Gets the DateFormat used to format the cell.  This will normally be
322    * the format specified in the excel spreadsheet, but in the event of any
323    * difficulty parsing this, it will revert to the default date/time format.
324    * 
325    * @return the DateFormat object used to format the date in the original 
326    *     excel cell
327    */
328   public DateFormat   getDateFormat()
329   {
330     return null;
331   }
332 }
333 
334 
335 
336
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