287 lines
12 KiB
XML
287 lines
12 KiB
XML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE faqs PUBLIC "-//APACHE//DTD FAQ V1.1//EN" "./dtd/faq-v11.dtd">
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<faqs title="Frequently Asked Questions">
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<faq>
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<question>
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Why is reading a simple sheet taking so long?
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</question>
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<answer>
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<p>You've probably enabled logging. Logging is intended only for
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autopsie style debugging. Having it enabled will reduce performance
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by a factor of at least 100. Logging is helpful for understanding
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why POI can't read some file or developing POI itself. Important
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errors are thrown as exceptions, which means you probably don't need
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logging.</p>
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</answer>
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</faq>
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<faq>
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<question>
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What is the HSSF "eventmodel"?
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</question>
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<answer>
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<p>The HSSF eventmodel package is a new API for reading XLS files more efficiently. It does
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require more knowledge on the part of the user, but reduces memory consumption by more than
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tenfold. It is based on the AWT event model in combination with SAX. If you need read-only
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access to a given XLS file, this is the best way to do it.</p>
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</answer>
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</faq>
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<faq>
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<question>
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Why can't read the document I created using Star Office 5.1?
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</question>
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<answer>
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<p>Star Office 5.1 writes some records using the older BIFF standard. This causes some problems
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with POI which supports only BIFF8.</p>
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</answer>
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</faq>
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<faq>
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<question>
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Why am I getting an exception each time I attempt to read my spreadsheet?
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</question>
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<answer>
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<p>It's possible your spreadsheet contains a feature that is not currently supported by HSSF.
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For example - spreadsheets containing cells with rich text are not currently supported.</p>
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</answer>
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</faq>
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<faq>
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<question>
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Does HSSF support protected spreadsheets?
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</question>
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<answer>
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<p>Protecting a spreadsheet encrypts it. We wont touch encryption because we're not legally educated
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and don't understand the full implications of trying to implement this. If you wish to have a go
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at this feel free to add it as a plugin module. We wont be hosting it here however.</p>
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</answer>
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</faq>
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<faq>
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<question>
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How do you tell if a field contains a date with HSSF?
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</question>
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<answer>
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<p>Excel stores dates as numbers therefore the only way to determine if a cell is
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actually stored as a date is to look at the formatting. There is a helper method
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in HSSFDateUtil (since the 1.7.0-dev release) that checks for this.
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Thanks to Jason Hoffman for providing the solution.</p>
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<source>
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case HSSFCell.CELL_TYPE_NUMERIC:
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double d = cell.getNumericCellValue();
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// test if a date!
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if (HSSFDateUtil.isCellDateFormatted(cell)) {
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// format in form of M/D/YY
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cal.setTime(HSSFDateUtil.getJavaDate(d));
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cellText =
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(String.valueOf(cal.get(Calendar.YEAR))).substring(2);
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cellText = cal.get(Calendar.MONTH)+1 + "/" +
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cal.get(Calendar.DAY_OF_MONTH) + "/" +
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cellText;
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} </source>
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</answer>
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</faq>
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<faq>
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<question>
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I'm trying to stream an XLS file from a servlet and I'm having some trouble. What's the problem?
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</question>
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<answer>
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<p>
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The problem usually manifests itself as the junk characters being shown on
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screen. The problem persists even though you have set the correct mime type.
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</p>
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<p>
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The short answer is, don't depend on IE to display a binary file type properly if you stream it via a
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servlet. Every minor version of IE has different bugs on this issue.
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</p>
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<p>
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The problem in most versions of IE is that it does not use the mime type on
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the HTTP response to determine the file type; rather it uses the file extension
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on the request. Thus you might want to add a
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<strong>.xls</strong> to your request
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string. For example
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<em>http://yourserver.com/myServelet.xls?param1=xx</em>. This is
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easily accomplished through URL mapping in any servlet container. Sometimes
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a request like
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<em>http://yourserver.com/myServelet?param1=xx&dummy=file.xls</em> is also
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known to work.
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</p>
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<p>
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To guarantee opening the file properly in Excel from IE, write out your file to a
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temporary file under your web root from your servelet. Then send an http response
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to the browser to do a client side redirection to your temp file. (Note that using a
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server side redirect using RequestDispatcher will not be effective in this case)
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</p>
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<p>
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Note also that when you request a document that is opened with an
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external handler, IE sometimes makes two requests to the webserver. So if your
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generating process is heavy, it makes sense to write out to a temporary file, so that multiple
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requests happen for a static file.
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</p>
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<p>
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None of this is particular to Excel. The same problem arises when you try to
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generate any binary file dynamically to an IE client. For example, if you generate
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pdf files using
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<link href="http://xml.apache.org/fop">FOP</link>, you will come across many of the same issues.
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</p>
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<!-- Thanks to Avik for the answer -->
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</answer>
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</faq>
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<faq>
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<question>
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I want to set a cell format (Data format of a cell) of a excel sheet as ###,###,###.#### or ###,###,###.0000. Is it possible using POI ?
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</question>
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<answer>
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<p>
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Yes. You first need to get a HSSFDataFormat object from the workbook and call getFormat with the desired format. Some examples are <link href="hssf/quick-guide.html#DataFormats">here</link>.
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</p>
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</answer>
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</faq>
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<faq>
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<question>
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I want to set a cell format (Data format of a cell) of a excel sheet as text. Is it possible using POI ?
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</question>
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<answer>
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<p>
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Yes. This is a built-in format for excel that you can get from HSSFDataFormat object using the format string "@". Also, the string "text" will alias this format.
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</p>
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</answer>
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</faq>
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<faq>
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<question>
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How do I add a border around a merged cell?
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</question>
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<answer>
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<p>Add blank cells around where the cells normally would have been and set the borders individually for each cell.
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We will probably enhance HSSF in the future to make this process easier.</p>
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</answer>
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</faq>
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<faq>
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<question>
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I tried to set cell values and Excel sheet name on my native language,
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but I failed to do it. :(
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</question>
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<answer>
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<p>By default HSSF uses cell values and sheet names as compressed unicode,
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so to support localization you should use Unicode.
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To do it you should set it manually:</p>
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<source>
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// for sheet name
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HSSFWorkbook wb = new HSSFWorkbook();
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HSSFSheet s = wb.createSheet();
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wb.setSheetName( 0, "SomeUnicodeName", HSSFWorkbook.ENCODING_UTF_16 );
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// for cell value
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HSSFRow r = s.createRow( 0 );
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HSSFCell c = r.createCell( (short)0 );
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c.setCellType( HSSFCell.CELL_TYPE_STRING );
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c.setEncoding( HSSFCell.ENCODING_UTF_16 );
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c.setCellValue( "\u0422\u0435\u0441\u0442\u043E\u0432\u0430\u044F" ); </source>
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<p>
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Make sure you make the call to setEncoding() before calling setCellValue(), otherwise what you pass in won't be interpreted properly.
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</p>
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</answer>
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</faq>
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<faq>
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<question>
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I'm having trouble creating a spreadsheet using POI using
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websphere 3.5.
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</question>
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<answer>
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<p>Make sure you have fix pack 4 installed.</p>
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</answer>
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</faq>
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<faq>
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<question>
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I am using styles when creating a workbook in POI, but Excel refuses to open the file, complaining about "Too Many Styles".
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</question>
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<answer>
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<p>You just create the styles OUTSIDE of the loop in which you create cells.</p>
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<p>GOOD:</p>
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<source>
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HSSFWorkbook wb = new HSSFWorkbook();
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HSSFSheet sheet = wb.createSheet("new sheet");
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HSSFRow row = null;
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// Aqua background
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HSSFCellStyle style = wb.createCellStyle();
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style.setFillBackgroundColor(HSSFColor.AQUA.index);
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style.setFillPattern(HSSFCellStyle.BIG_SPOTS);
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HSSFCell cell = row.createCell((short) 1);
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cell.setCellValue("X");
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cell.setCellStyle(style);
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// Orange "foreground", foreground being the fill foreground not the font color.
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style = wb.createCellStyle();
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style.setFillForegroundColor(HSSFColor.ORANGE.index);
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style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
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for (int x = 0; x < 1000; x++) {
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// Create a row and put some cells in it. Rows are 0 based.
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row = sheet.createRow((short) k);
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for (int y = 0; y < 100; y++) {
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cell = row.createCell((short) k);
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cell.setCellValue("X");
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cell.setCellStyle(style);
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}
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}
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// Write the output to a file
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FileOutputStream fileOut = new FileOutputStream("workbook.xls");
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wb.write(fileOut);
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fileOut.close(); </source>
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<p>BAD:</p>
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<source>
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HSSFWorkbook wb = new HSSFWorkbook();
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HSSFSheet sheet = wb.createSheet("new sheet");
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HSSFRow row = null;
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for (int x = 0; x < 1000; x++) {
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// Aqua background
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HSSFCellStyle style = wb.createCellStyle();
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style.setFillBackgroundColor(HSSFColor.AQUA.index);
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style.setFillPattern(HSSFCellStyle.BIG_SPOTS);
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HSSFCell cell = row.createCell((short) 1);
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cell.setCellValue("X");
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cell.setCellStyle(style);
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// Orange "foreground", foreground being the fill foreground not the font color.
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style = wb.createCellStyle();
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style.setFillForegroundColor(HSSFColor.ORANGE.index);
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style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
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// Create a row and put some cells in it. Rows are 0 based.
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row = sheet.createRow((short) k);
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for (int y = 0; y < 100; y++) {
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cell = row.createCell((short) k);
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cell.setCellValue("X");
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cell.setCellStyle(style);
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}
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}
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// Write the output to a file
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FileOutputStream fileOut = new FileOutputStream("workbook.xls");
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wb.write(fileOut);
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fileOut.close(); </source>
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</answer>
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</faq>
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<faq>
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<question>
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Will Poi read any spreadsheet and rewrite it with modifications.
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</question>
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<answer>
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<p>Poi is not guanteed to read the contents of any spreadsheet.
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Certain features may cause spreadsheets to fail to read. More
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problematic is rewriting spreadsheets. Poi tried hard to
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preserve the records of the original spreadsheet but some
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features may cause problems. We advise that you limit the
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formatting of spreadsheets you process so as to not be
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unpleasantly suprised at a later stage.</p>
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</answer>
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</faq>
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</faqs>
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