1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
|
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.1//EN" "../dtd/document-v11.dtd">
<document>
<header>
<title>The New Halloween Document</title>
<authors>
<person email="acoliver2@users.sourceforge.net" name="Andrew C. Oliver" id="AO"/>
<person email="glens@apache.org" name="Glen Stampoultzis" id="GJS"/>
</authors>
</header>
<body>
<section title="How to use the HSSF prototype API">
<section title="Capabilities">
<p>This release of the how-to outlines functionality for the 1.5 release.
Those looking for information on previous releases should
look in the documentation distributed with that release.</p>
<p>
This release allows numeric and string cell values to be written to
or read from an XLS file as well as reading and writing dates. Also
in this release is row and column sizing, cell styling (bold,
italics, borders,etc), and support for built-in data formats. New
to this release is an event-based API for reading XLS files.
It differs greatly from the read/write API
and is intended for intermediate developers who need a smaller
memory footprint. It will also serve as the basis for the HSSF
Generator.</p>
</section>
<section title="General Use">
<section title="User API">
<section title="Writing a new one">
<p>The high level API (package: org.apache.poi.hssf.usermodel)
is what most people should use. Usage is very simple.
</p>
<p>Workbooks are created by creating an instance of
org.apache.poi.hssf.usermodel.HSSFWorkbook.
</p>
<p>Sheets are created by calling createSheet() from an existing
instance of HSSFWorkbook, the created sheet is automatically added in
sequence to the workbook. Sheets do not in themselves have a sheet
name (the tab at the bottom); you set
the name associated with a sheet by calling
HSSFWorkbook.setSheetName(sheetindex,"SheetName").</p>
<p>Rows are created by calling createRow(rowNumber) from an existing
instance of HSSFSheet. Only rows that have cell values should be
added to the sheet. To set the row's height, you just call
setRowHeight(height) on the row object. The height must be given in
twips, or 1/20th of a point. If you prefer, there is also a
setRowHeightInPoints method.
</p>
<p>Cells are created by calling createCell(column, type) from an
existing HSSFRow. Only cells that have values should be added to the
row. Cells should have their cell type set to either
HSSFCell.CELL_TYPE_NUMERIC or HSSFCell.CELL_TYPE_STRING depending on
whether they contain a numeric or textual value. Cells must also have
a value set. Set the value by calling setCellValue with either a
String or double as a parameter. Individual cells do not have a
width; you must call setColumnWidth(colindex, width) (use units of
1/256th of a character) on the HSSFSheet object. (You can't do it on
an individual basis in the GUI either).</p>
<p>Cells are styled with HSSFCellStyle objects which in turn contain
a reference to an HSSFFont object. These are created via the
HSSFWorkbook object by calling createCellStyle() and createFont().
Once you create the object you must set its parameters (colors,
borders, etc). To set a font for an HSSFCellStyle call
setFont(fontobj).
</p>
<p>Once you have generated your workbook, you can write it out by
calling write(outputStream) from your instance of Workbook, passing
it an OutputStream (for instance, a FileOutputStream or
ServletOutputStream). You must close the OutputStream yourself. HSSF
does not close it for you.
</p>
<p>Here is some example code (excerpted and adapted from
org.apache.poi.hssf.dev.HSSF test class):</p>
<source><"));
//set a thin border
cs2.setBorderBottom(cs2.BORDER_THIN);
//fill w fg fill color
cs2.setFillPattern((short) HSSFCellStyle.SOLID_FOREGROUND);
// set foreground fill to red
cs2.setFillForegroundColor((short) HSSFColor.RED.index);
// set the font
cs2.setFont(f2);
// set the sheet name to HSSF Test
wb.setSheetName(0, "HSSF Test");
// create a sheet with 300 rows (0-299)
for (rownum = (short) 0; rownum < 300; rownum++)
{
// create a row
r = s.createRow(rownum);
// on every other row
if ((rownum % 2) == 0)
{
// make the row height bigger (in twips - 1/20 of a point)
r.setHeight((short) 0x249);
}
//r.setRowNum(( short ) rownum);
// create 50 cells (0-49) (the += 2 becomes apparent later
for (short cellnum = (short) 0; cellnum < 50; cellnum += 2)
{
// create a numeric cell
c = r.createCell(cellnum);
// do some goofy math to demonstrate decimals
c.setCellValue(rownum * 10000 + cellnum
+ (((double) rownum / 1000)
+ ((double) cellnum / 10000)));
// on every other row
if ((rownum % 2) == 0)
{
// set this cell to the first cell style we defined
c.setCellStyle(cs);
}
// create a string cell (see why += 2 in the
c = r.createCell((short) (cellnum + 1));
// set the cell's string value to "TEST"
c.setCellValue("TEST");
// make this column a bit wider
s.setColumnWidth((short) (cellnum + 1), (short) ((50 * 8) / ((double) 1 / 20)));
// on every other row
if ((rownum % 2) == 0)
{
// set this to the white on red cell style
// we defined above
c.setCellStyle(cs2);
}
}
}
//draw a thick black border on the row at the bottom using BLANKS
// advance 2 rows
rownum++;
rownum++;
r = s.createRow(rownum);
// define the third style to be the default
// except with a thick black border at the bottom
cs3.setBorderBottom(cs3.BORDER_THICK);
//create 50 cells
for (short cellnum = (short) 0; cellnum < 50; cellnum++)
{
//create a blank type cell (no value)
c = r.createCell(cellnum);
// set it to the thick black border style
c.setCellStyle(cs3);
}
//end draw thick black border
// demonstrate adding/naming and deleting a sheet
// create a sheet, set its title then delete it
s = wb.createSheet();
wb.setSheetName(1, "DeletedSheet");
wb.removeSheetAt(1);
//end deleted sheet
// write the workbook to the output stream
// close our file (don't blow out our file handles
wb.write(out);
out.close();
]]></source>
</section>
<section title="Reading or modifying an existing file">
<p>Reading in a file is equally simple. To read in a file, create a
new instance of org.apache.poi.poifs.Filesystem, passing in an open InputStream, such as a FileInputStream
for your XLS, to the constructor. Construct a new instance of
org.apache.poi.hssf.usermodel.HSSFWorkbook passing the
Filesystem instance to the constructor. From there you have access to
all of the high level model objects through their assessor methods
(workbook.getSheet(sheetNum), sheet.getRow(rownum), etc).
</p>
<p>Modifying the file you have read in is simple. You retrieve the
object via an assessor method, remove it via a parent object's remove
method (sheet.removeRow(hssfrow)) and create objects just as you
would if creating a new xls. When you are done modifying cells just
call workbook.write(outputstream) just as you did above.</p>
<p>An example of this can be seen in
<link href="http://cvs.apache.org/viewcvs/~checkout~/jakarta-poi/src/java/org/apache/poi/hssf/dev/HSSF.java?rev=1.1">org.apache.poi.hssf.dev.HSSF</link>.</p>
</section>
</section>
<section title="Event API">
<p>The event API is brand new. It is intended for intermediate
developers who are willing to learn a little bit of the low level API
structures. Its relatively simple to use, but requires a basic
understanding of the parts of an Excel file (or willingness to
learn). The advantage provided is that you can read an XLS with a
relatively small memory footprint.
</p>
<p>To use this API you construct an instance of
org.apache.poi.hssf.eventmodel.HSSFRequest. Register a class you
create that supports the
org.apache.poi.hssf.eventmodel.HSSFListener interface using the
HSSFRequest.addListener(yourlistener, recordsid). The recordsid
should be a static reference number (such as BOFRecord.sid) contained
in the classes in org.apache.poi.hssf.record. The trick is you
have to know what these records are. Alternatively you can call
HSSFRequest.addListenerForAllRecords(mylistener). In order to learn
about these records you can either read all of the javadoc in the
org.apache.poi.hssf.record package or you can just hack up a
copy of org.apache.poi.hssf.dev.EFHSSF and adapt it to your
needs. TODO: better documentation on records.</p>
<p>Once you've registered your listeners in the HSSFRequest object
you can construct an instance of
org.apache.poi.poifs.filesystem.FileSystem (see POIFS howto) and
pass it your XLS file inputstream. You can either pass this, along
with the request you constructed, to an instance of HSSFEventFactory
via the HSSFEventFactory.processWorkbookEvents(request, Filesystem)
method, or you can get an instance of DocumentInputStream from
Filesystem.createDocumentInputStream("Workbook") and pass
it to HSSFEventFactory.processEvents(request, inputStream). Once you
make this call, the listeners that you constructed receive calls to
their processRecord(Record) methods with each Record they are
registered to listen for until the file has been completely read.
</p>
<p>A code excerpt from org.apache.poi.hssf.dev.EFHSSF (which is
in CVS or the source distribution) is reprinted below with excessive
comments:</p>
<source><![CDATA[
/**
* This example shows how to use the event API for reading a file.
*/
public class EventExample
implements HSSFListener
{
private SSTRecord sstrec;
/**
* This method listens for incoming records and handles them as required.
* @param record The record that was found while reading.
*/
public void processRecord(Record record)
{
switch (record.getSid())
{
// the BOFRecord can represent either the beginning of a sheet or the workbook
case BOFRecord.sid:
BOFRecord bof = (BOFRecord) record;
if (bof.getType() == bof.TYPE_WORKBOOK)
{
System.out.println("Encountered workbook");
// assigned to the class level member
} else if (bof.getType() == bof.TYPE_WORKSHEET)
{
System.out.println("Encountered sheet reference");
}
break;
case BoundSheetRecord.sid:
BoundSheetRecord bsr = (BoundSheetRecord) record;
System.out.println("New sheet named: " + bsr.getSheetname());
break;
case RowRecord.sid:
RowRecord rowrec = (RowRecord) record;
System.out.println("Row found, first column at "
+ rowrec.getFirstCol() + " last column at " + rowrec.getLastCol());
break;
case NumberRecord.sid:
NumberRecord numrec = (NumberRecord) record;
System.out.println("Cell found with value " + numrec.getValue()
+ " at row " + numrec.getRow() + " and column " + numrec.getColumn());
break;
// SSTRecords store a array of unique strings used in Excel.
case SSTRecord.sid:
sstrec = (SSTRecord) record;
for (int k = 0; k < sstrec.getNumUniqueStrings(); k++)
{
System.out.println("String table value " + k + " = " + sstrec.getString(k));
}
break;
case LabelSSTRecord.sid:
LabelSSTRecord lrec = (LabelSSTRecord) record;
System.out.println("String cell found with value "
+ sstrec.getString(lrec.getSSTIndex()));
break;
}
}
/**
* Read an excel file and spit out what we find.
*
* @param args Expect one argument that is the file to read.
* @throws IOException When there is an error processing the file.
*/
public static void main(String[] args) throws IOException
{
// create a new file input stream with the input file specified
// at the command line
FileInputStream fin = new FileInputStream(args[0]);
// create a new org.apache.poi.poifs.filesystem.Filesystem
POIFSFileSystem poifs = new POIFSFileSystem(fin);
// get the Workbook (excel part) stream in a InputStream
InputStream din = poifs.createDocumentInputStream("Workbook");
// construct out HSSFRequest object
HSSFRequest req = new HSSFRequest();
// lazy listen for ALL records with the listener shown above
req.addListenerForAllRecords(new EventExample());
// create our event factory
HSSFEventFactory factory = new HSSFEventFactory();
// process our events based on the document input stream
factory.processEvents(req, din);
// once all the events are processed close our file input stream
fin.close();
// and our document input stream (don't want to leak these!)
din.close();
System.out.println("done.");
}
}
]]></source>
</section>
<section title="Low Level APIs">
<p>The low level API is not much to look at. It consists of lots of
"Records" in the org.apache.poi.hssf.record.* package,
and set of helper classes in org.apache.poi.hssf.model.*. The
record classes are consistent with the low level binary structures
inside a BIFF8 file (which is embedded in a POIFS file system). You
probably need the book: "Microsoft Excel 97 Developer's Kit"
from Microsoft Press in order to understand how these fit together
(out of print but easily obtainable from Amazon's used books). In
order to gain a good understanding of how to use the low level APIs
should view the source in org.apache.poi.hssf.usermodel.* and
the classes in org.apache.poi.hssf.model.*. You should read the
documentation for the POIFS libraries as well.</p>
</section>
<section title="HSSF Class/Test Application">
<p>The HSSF application is nothing more than a test for the high
level API (and indirectly the low level support). The main body of
its code is repeated above. To run it:
</p>
<ul>
<li>download the poi-alpha build and untar it (tar xvzf
tarball.tar.gz)
</li>
<li>set up your classpath as follows:
<code>export HSSFDIR={wherever you put HSSF's jar files}
export LOG4JDIR={wherever you put LOG4J's jar files}
export CLASSPATH=$CLASSPATH:$HSSFDIR/hssf.jar:$HSSFDIR/poi-poifs.jar:$HSSFDIR/poi-util.jar:$LOG4JDIR/jog4j.jar</code>
</li><li>type:
<code>java org.apache.poi.hssf.dev.HSSF ~/myxls.xls write</code></li>
</ul>
<p></p>
<p>This should generate a test sheet in your home directory called <code>"myxls.xls"</code>. </p>
<ul>
<li>Type:
<code>java org.apache.poi.hssf.dev.HSSF ~/input.xls output.xls</code>
<p>
This is the read/write/modify test. It reads in the spreadsheet, modifies a cell, and writes it back out.
Failing this test is not necessarily a bad thing. If HSSF tries to modify a non-existant sheet then this will
most likely fail. No big deal. </p></li>
</ul>
</section>
<section title="HSSF Logging facility">
<p>HSSF now has a logging facility (using
<link href="http://jakarta.apache.org/commons/logging.html">commons logging</link>)
that will record massive amounts of debugging information. Its mostly
useful to us hssf-developing geeks, but might be useful in tracking
down problems.
</p>
<p>So Why use commons logging rather than log4j? Well the following discussion from
the jakarta-general mailing list sums it up pretty well. (Thanks Morgan)
</p>
<p><em>Here's the problem, as I see it.</em>
</p>
<p><em>Suppose Commons component A decides to adopt Log4J, Commons component B
decides to adopt LogKit, and Commons component C adopts JDK1.4 logging.
They will all minimally function with the right jars in the classpath.
However you (the end-user) are left with maintaining configuration for 3
different logging APIs, which is tedious at best. When you take into
account cool features like variable log levels, Log4J appenders and the
like, you're pretty much guaranteed to swallow up useful configuration
options because sophisticated configurations are too difficult to maintain
over mutiple logging implementations.</em>
</p>
<p>
<em>Contrarily, if all three Commons components use a logging facade, you can
focus all your configuration efforts on one logging implementation. Sure,
there is a trade-off; you don't have access to all the features, and the
interface between the facade and the implementation must be maintained. But
the benefits are not just political; they potentially make the end-users
configuration much easier.</em>
</p>
<p><em>Even if all Commons components used the same logging implementation (Log4J
for example), other projects in Jakarta-land may choose otherwise. If you
add enough Jakarta projects to your environment, you eventually end up with
the scenario described above. It's a worthwhile effort to attempt a logging
solution that plays well with the Jakarta community at large. I think in
many cases the Commons Logging component can fill that role.</em>
</p>
<p>
Refer to the commons logging package level javadoc for more information concerning how to
<link href="http://jakarta.apache.org/commons/logging/api/index.html">configure commons logging.</link>
</p>
</section>
<section title="HSSF Developer's tools">
<p>HSSF has a number of tools useful for developers to debug/develop
stuff using HSSF (and more generally XLS files). We've already
discussed the app for testing HSSF read/write/modify capabilities;
now we'll talk a bit about BiffViewer. Early on in the development of
HSSF, it was decided that knowing what was in a record, what was
wrong with it, etc. was virtually impossible with the available
tools. So we developed BiffViewer. You can find it at
org.apache.poi.hssf.dev.BiffViewer. It performs two basic
functions and a derivative.
</p>
<p>The first is "biffview". To do this you run it (assumes
you have everything setup in your classpath and that you know what
you're doing enough to be thinking about this) with an xls file as a
parameter. It will give you a listing of all understood records with
their data and a list of not-yet-understood records with no data
(because it doesn't know how to interpret them). This listing is
useful for several things. First, you can look at the values and SEE
what is wrong in quasi-English. Second, you can send the output to a
file and compare it.
</p>
<p>The second function is "big freakin dump", just pass a
file and a second argument matching "bfd" exactly. This
will just make a big hexdump of the file.
</p>
<p>Lastly, there is "mixed" mode which does the same as
regular biffview, only it includes hex dumps of certain records
intertwined. To use that just pass a file with a second argument
matching "on" exactly.</p>
<p>In the next release cycle we'll also have something called a
FormulaViewer. The class is already there, but its not very useful
yet. When it does something, we'll document it.</p>
</section>
<section title="What's Next?">
<p>This release contains code that supports "internationalization"
or more accurately non-US/UK languages; however, it has not been
tested with the new API changes (please help us with this). We've
shifted focus a bit for this release in recognition of the
international support we've gotten. We're going to focus on western
European languages for our first beta. We're more than happy to
accept help in supporting non-Western European languages if someone
who knows what they're doing in this area is willing to pitch in!
(There is next to no documentation on what is necessary to support
such a move and its really hard to support a language when you don't even
know the alphabet).</p>
<p>This release of HSSF does not yet support Formulas. I've been
focusing on the requests I've gotten in. That being said, if we get
more user feedback on what is most useful first we'll aim for that.
As a general principal, HSSF's goal is to support HSSF-Serializer
(meaning an emphasis on write). We would like to hear from you! How
are you using HSSF/POIFS? How would you like to use it? What features
are most important first?
</p>
</section>
</section>
</section>
</body>
</document>
|
