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<h1>Frequently Asked Questions</h1>
</div>
<div class="h3">
<a name="Questions"></a>
<div class="h3">
<h3>Questions</h3>
</div>
<ol>
<li>
<a name="faq-N10006-menu"></a><a href="#faq-N10006">
My code uses some new feature, compiles fine but fails when live with a "MethodNotFoundException"
</a>
</li>
<li>
<a name="faq-N10019-menu"></a><a href="#faq-N10019">
My code uses the scratchpad, compiles fine but fails to run with a "MethodNotFoundException"
</a>
</li>
<li>
<a name="faq-N10025-menu"></a><a href="#faq-N10025">
I'm using the poi-ooxml-schemas jar, but my code is failing with "java.lang.NoClassDefFoundError: org/openxmlformats/schemas/*something*"
</a>
</li>
<li>
<a name="faq-N1005A-menu"></a><a href="#faq-N1005A">
Why is reading a simple sheet taking so long?
</a>
</li>
<li>
<a name="faq-N10066-menu"></a><a href="#faq-N10066">
What is the HSSF "eventmodel"?
</a>
</li>
<li>
<a name="faq-N10072-menu"></a><a href="#faq-N10072">
Why can't read the document I created using Star Office 5.1?
</a>
</li>
<li>
<a name="faq-N1007E-menu"></a><a href="#faq-N1007E">
Why am I getting an exception each time I attempt to read my spreadsheet?
</a>
</li>
<li>
<a name="faq-N1008D-menu"></a><a href="#faq-N1008D">
How do you tell if a spreadsheet cell contains a date?
</a>
</li>
<li>
<a name="faq-N1009D-menu"></a><a href="#faq-N1009D">
I'm trying to stream an XLS file from a servlet and I'm having some trouble. What's the problem?
</a>
</li>
<li>
<a name="faq-N100C7-menu"></a><a href="#faq-N100C7">
I want to set a cell format (Data format of a cell) of a excel sheet as ###,###,###.#### or ###,###,###.0000. Is it possible using POI ?
</a>
</li>
<li>
<a name="faq-N100D7-menu"></a><a href="#faq-N100D7">
I want to set a cell format (Data format of a cell) of a excel sheet as text. Is it possible using POI ?
</a>
</li>
<li>
<a name="faq-N100E3-menu"></a><a href="#faq-N100E3">
How do I add a border around a merged cell?
</a>
</li>
<li>
<a name="faq-N100EF-menu"></a><a href="#faq-N100EF">
I am using styles when creating a workbook in POI, but Excel refuses to open the file, complaining about "Too Many Styles".
</a>
</li>
</ol>
<a name="Answers"></a>
<div class="h3">
<h3>Answers</h3>
</div>
<a name="faq-N10006"></a>
<div class="h4">
<h4>1.
My code uses some new feature, compiles fine but fails when live with a "MethodNotFoundException"
</h4>
</div>
<p>You almost certainly have an older version of POI
on your classpath. Quite a few runtimes and other packages
will ship an older version of POI, so this is an easy problem
to hit without your realising.</p>
<p>The best way to identify the offending earlier jar file is
with a few lines of java. These will load one of the core POI
classes, and report where it came from.</p>
<pre class="code">
ClassLoader classloader =
org.apache.poi.poifs.filesystem.POIFSFileSystem.class.getClassLoader();
URL res = classloader.getResource(
"org/apache/poi/poifs/filesystem/POIFSFileSystem.class");
String path = res.getPath();
System.out.println("Core POI came from " + path);
</pre>
<a name="faq-N10019"></a>
<div class="h4">
<h4>2.
My code uses the scratchpad, compiles fine but fails to run with a "MethodNotFoundException"
</h4>
</div>
<p>You almost certainly have an older version earlier on your
classpath. See the prior answer.</p>
<a name="faq-N10025"></a>
<div class="h4">
<h4>3.
I'm using the poi-ooxml-schemas jar, but my code is failing with "java.lang.NoClassDefFoundError: org/openxmlformats/schemas/*something*"
</h4>
</div>
<p>To use the new OOXML file formats, POI requires a jar containing
the file format XSDs, as compiled by
<a href="http://xmlbeans.apache.org/">XMLBeans</a>. These
XSDs, once compiled into Java classes, live in the
<em>org.openxmlformats.schemas</em> namespace.</p>
<p>There are two jar files available, as described in
<a href="/overview.html">the components overview section</a>.
The <em>full jar of all of the schemas is ooxml-schemas-1.1.jar</em>,
and it is currently around 15mb. The <em>smaller poi-ooxml-schemas
jar</em> is only about 4mb. This latter jar file only contains the
typically used parts though.</p>
<p>Many users choose to use the smaller poi-ooxml-schemas jar to save
space. However, the poi-ooxml-schemas jar only contains the XSDs and
classes that are typically used, as identified by the unit tests.
Every so often, you may try to use part of the file format which
isn't included in the minimal poi-ooxml-schemas jar. In this case,
you should switch to the full ooxml-schemas-1.1.jar. Longer term,
you may also wish to submit a new unit test which uses the extra
parts of the XSDs, so that a future poi-ooxml-schemas jar will
include them.</p>
<p>There are a number of ways to get the full ooxml-schemas-1.1.jar.
If you are a maven user, see the
<a href="/overview.html">the components overview section</a>
for the artifact details to have maven download it for you.
If you download the source release of POI, and/or checkout the
source code from <a href="/subversion.html">subversion</a>,
then you can run the ant task "compile-ooxml-xsds" to have the
OOXML schemas downloaded and compiled for you (This will also
give you the XMLBeans generated source code, in case you wish to
look at this). Finally, you can download the jar by hand from the
<a href="http://www.ibiblio.org/maven/org.apache.poi/jars/">POI
Maven Repository</a>.</p>
<p>Note that for POI 3.5 and 3.6, the full ooxml schemas jar was
named ooxml-schemas-1.0.jar. For POI 3.7, the filename was bumped
to ooxml-schemas-1.1.jar when generics support was added. You can
use ooxml-schemas-1.1.jar with POI 3.5 and 3.6 if you wish, but
POI 3.7 won't wokr with ooxml-schemas-1.0.jar (it needs thew newer
one).</p>
<a name="faq-N1005A"></a>
<div class="h4">
<h4>4.
Why is reading a simple sheet taking so long?
</h4>
</div>
<p>You've probably enabled logging. Logging is intended only for
autopsy style debugging. Having it enabled will reduce performance
by a factor of at least 100. Logging is helpful for understanding
why POI can't read some file or developing POI itself. Important
errors are thrown as exceptions, which means you probably don't need
logging.</p>
<a name="faq-N10066"></a>
<div class="h4">
<h4>5.
What is the HSSF "eventmodel"?
</h4>
</div>
<p>The SS eventmodel package is an API for reading Excel files without loading the whole spreadsheet into memory. It does
require more knowledge on the part of the user, but reduces memory consumption by more than
tenfold. It is based on the AWT event model in combination with SAX. If you need read-only
access, this is the best way to do it.</p>
<a name="faq-N10072"></a>
<div class="h4">
<h4>6.
Why can't read the document I created using Star Office 5.1?
</h4>
</div>
<p>Star Office 5.1 writes some records using the older BIFF standard. This causes some problems
with POI which supports only BIFF8.</p>
<a name="faq-N1007E"></a>
<div class="h4">
<h4>7.
Why am I getting an exception each time I attempt to read my spreadsheet?
</h4>
</div>
<p>It's possible your spreadsheet contains a feature that is not currently supported by POI.
If you encounter this then please create the simplest file that demonstrates the trouble and submit it to
<a href="http://issues.apache.org/bugzilla/buglist.cgi?product=POI">Bugzilla.</a>
</p>
<a name="faq-N1008D"></a>
<div class="h4">
<h4>8.
How do you tell if a spreadsheet cell contains a date?
</h4>
</div>
<p>Excel stores dates as numbers therefore the only way to determine if a cell is
actually stored as a date is to look at the formatting. There is a helper method
in HSSFDateUtil that checks for this.
Thanks to Jason Hoffman for providing the solution.</p>
<pre class="code">
case HSSFCell.CELL_TYPE_NUMERIC:
double d = cell.getNumericCellValue();
// test if a date!
if (HSSFDateUtil.isCellDateFormatted(cell)) {
// format in form of M/D/YY
cal.setTime(HSSFDateUtil.getJavaDate(d));
cellText =
(String.valueOf(cal.get(Calendar.YEAR))).substring(2);
cellText = cal.get(Calendar.MONTH)+1 + "/" +
cal.get(Calendar.DAY_OF_MONTH) + "/" +
cellText;
}
</pre>
<a name="faq-N1009D"></a>
<div class="h4">
<h4>9.
I'm trying to stream an XLS file from a servlet and I'm having some trouble. What's the problem?
</h4>
</div>
<p>
The problem usually manifests itself as the junk characters being shown on
screen. The problem persists even though you have set the correct mime type.
</p>
<p>
The short answer is, don't depend on IE to display a binary file type properly if you stream it via a
servlet. Every minor version of IE has different bugs on this issue.
</p>
<p>
The problem in most versions of IE is that it does not use the mime type on
the HTTP response to determine the file type; rather it uses the file extension
on the request. Thus you might want to add a
<strong>.xls</strong> to your request
string. For example
<em>http://yourserver.com/myServelet.xls?param1=xx</em>. This is
easily accomplished through URL mapping in any servlet container. Sometimes
a request like
<em>http://yourserver.com/myServelet?param1=xx&dummy=file.xls</em> is also
known to work.
</p>
<p>
To guarantee opening the file properly in Excel from IE, write out your file to a
temporary file under your web root from your servelet. Then send an http response
to the browser to do a client side redirection to your temp file. (Note that using a
server side redirect using RequestDispatcher will not be effective in this case)
</p>
<p>
Note also that when you request a document that is opened with an
external handler, IE sometimes makes two requests to the webserver. So if your
generating process is heavy, it makes sense to write out to a temporary file, so that multiple
requests happen for a static file.
</p>
<p>
None of this is particular to Excel. The same problem arises when you try to
generate any binary file dynamically to an IE client. For example, if you generate
pdf files using
<a href="http://xml.apache.org/fop">FOP</a>, you will come across many of the same issues.
</p>
<a name="faq-N100C7"></a>
<div class="h4">
<h4>10.
I want to set a cell format (Data format of a cell) of a excel sheet as ###,###,###.#### or ###,###,###.0000. Is it possible using POI ?
</h4>
</div>
<p>
Yes. You first need to get a DataFormat object from the workbook and call getFormat with the desired format. Some examples are <a href="spreadsheet/quick-guide.html#DataFormats">here</a>.
</p>
<a name="faq-N100D7"></a>
<div class="h4">
<h4>11.
I want to set a cell format (Data format of a cell) of a excel sheet as text. Is it possible using POI ?
</h4>
</div>
<p>
Yes. This is a built-in format for excel that you can get from DataFormat object using the format string "@". Also, the string "text" will alias this format.
</p>
<a name="faq-N100E3"></a>
<div class="h4">
<h4>12.
How do I add a border around a merged cell?
</h4>
</div>
<p>Add blank cells around where the cells normally would have been and set the borders individually for each cell.
We will probably enhance HSSF in the future to make this process easier.</p>
<a name="faq-N100EF"></a>
<div class="h4">
<h4>13.
I am using styles when creating a workbook in POI, but Excel refuses to open the file, complaining about "Too Many Styles".
</h4>
</div>
<p>You just create the styles OUTSIDE of the loop in which you create cells.</p>
<p>GOOD:</p>
<pre class="code">
HSSFWorkbook wb = new HSSFWorkbook();
HSSFSheet sheet = wb.createSheet("new sheet");
HSSFRow row = null;
// Aqua background
HSSFCellStyle style = wb.createCellStyle();
style.setFillBackgroundColor(HSSFColor.AQUA.index);
style.setFillPattern(HSSFCellStyle.BIG_SPOTS);
HSSFCell cell = row.createCell((short) 1);
cell.setCellValue("X");
cell.setCellStyle(style);
// Orange "foreground",
// foreground being the fill foreground not the font color.
style = wb.createCellStyle();
style.setFillForegroundColor(HSSFColor.ORANGE.index);
style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
for (int x = 0; x < 1000; x++) {
// Create a row and put some cells in it. Rows are 0 based.
row = sheet.createRow((short) k);
for (int y = 0; y < 100; y++) {
cell = row.createCell((short) k);
cell.setCellValue("X");
cell.setCellStyle(style);
}
}
// Write the output to a file
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();
</pre>
<p>BAD:</p>
<pre class="code">
HSSFWorkbook wb = new HSSFWorkbook();
HSSFSheet sheet = wb.createSheet("new sheet");
HSSFRow row = null;
for (int x = 0; x < 1000; x++) {
// Aqua background
HSSFCellStyle style = wb.createCellStyle();
style.setFillBackgroundColor(HSSFColor.AQUA.index);
style.setFillPattern(HSSFCellStyle.BIG_SPOTS);
HSSFCell cell = row.createCell((short) 1);
cell.setCellValue("X");
cell.setCellStyle(style);
// Orange "foreground",
// foreground being the fill foreground not the font color.
style = wb.createCellStyle();
style.setFillForegroundColor(HSSFColor.ORANGE.index);
style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
// Create a row and put some cells in it. Rows are 0 based.
row = sheet.createRow((short) k);
for (int y = 0; y < 100; y++) {
cell = row.createCell((short) k);
cell.setCellValue("X");
cell.setCellStyle(style);
}
}
// Write the output to a file
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();
</pre>
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