476 lines
22 KiB
XML
476 lines
22 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.1//EN" "../dtd/document-v11.dtd">
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<document>
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<header>
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<title>The New Halloween Document</title>
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<authors>
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<person email="acoliver2@users.sourceforge.net" name="Andrew C. Oliver" id="AO"/>
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<person email="glens@apache.org" name="Glen Stampoultzis" id="GJS"/>
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</authors>
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</header>
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<body>
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<section title="How to use the HSSF prototype API">
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<section title="Capabilities">
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<p>This release of the how-to outlines functionality for the 1.5 release.
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Those looking for information on previous releases should
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look in the documentation distributed with that release.</p>
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<p>
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This release allows numeric and string cell values to be written to
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or read from an XLS file as well as reading and writing dates. Also
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in this release is row and column sizing, cell styling (bold,
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italics, borders,etc), and support for built-in data formats. New
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to this release is an event-based API for reading XLS files.
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It differs greatly from the read/write API
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and is intended for intermediate developers who need a smaller
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memory footprint. It will also serve as the basis for the HSSF
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Generator.</p>
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</section>
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<section title="General Use">
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<section title="User API">
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<section title="Writing a new one">
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<p>The high level API (package: org.apache.poi.hssf.usermodel)
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is what most people should use. Usage is very simple.
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</p>
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<p>Workbooks are created by creating an instance of
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org.apache.poi.hssf.usermodel.HSSFWorkbook.
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</p>
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<p>Sheets are created by calling createSheet() from an existing
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instance of HSSFWorkbook, the created sheet is automatically added in
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sequence to the workbook. Sheets do not in themselves have a sheet
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name (the tab at the bottom); you set
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the name associated with a sheet by calling
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HSSFWorkbook.setSheetName(sheetindex,"SheetName").</p>
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<p>Rows are created by calling createRow(rowNumber) from an existing
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instance of HSSFSheet. Only rows that have cell values should be
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added to the sheet. To set the row's height, you just call
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setRowHeight(height) on the row object. The height must be given in
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twips, or 1/20th of a point. If you prefer, there is also a
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setRowHeightInPoints method.
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</p>
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<p>Cells are created by calling createCell(column, type) from an
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existing HSSFRow. Only cells that have values should be added to the
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row. Cells should have their cell type set to either
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HSSFCell.CELL_TYPE_NUMERIC or HSSFCell.CELL_TYPE_STRING depending on
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whether they contain a numeric or textual value. Cells must also have
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a value set. Set the value by calling setCellValue with either a
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String or double as a parameter. Individual cells do not have a
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width; you must call setColumnWidth(colindex, width) (use units of
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1/256th of a character) on the HSSFSheet object. (You can't do it on
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an individual basis in the GUI either).</p>
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<p>Cells are styled with HSSFCellStyle objects which in turn contain
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a reference to an HSSFFont object. These are created via the
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HSSFWorkbook object by calling createCellStyle() and createFont().
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Once you create the object you must set its parameters (colors,
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borders, etc). To set a font for an HSSFCellStyle call
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setFont(fontobj).
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</p>
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<p>Once you have generated your workbook, you can write it out by
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calling write(outputStream) from your instance of Workbook, passing
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it an OutputStream (for instance, a FileOutputStream or
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ServletOutputStream). You must close the OutputStream yourself. HSSF
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does not close it for you.
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</p>
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<p>Here is some example code (excerpted and adapted from
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org.apache.poi.hssf.dev.HSSF test class):</p>
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<source><"));
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//set a thin border
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cs2.setBorderBottom(cs2.BORDER_THIN);
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//fill w fg fill color
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cs2.setFillPattern((short) HSSFCellStyle.SOLID_FOREGROUND);
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// set foreground fill to red
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cs2.setFillForegroundColor((short) HSSFCellStyle.RED);
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// set the font
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cs2.setFont(f2);
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// set the sheet name to HSSF Test
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wb.setSheetName(0, "HSSF Test");
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// create a sheet with 300 rows (0-299)
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for (rownum = (short) 0; rownum < 300; rownum++)
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{
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// create a row
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r = s.createRow(rownum);
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// on every other row
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if ((rownum % 2) == 0)
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{
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// make the row height bigger (in twips - 1/20 of a point)
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r.setHeight((short) 0x249);
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}
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//r.setRowNum(( short ) rownum);
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// create 50 cells (0-49) (the += 2 becomes apparent later
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for (short cellnum = (short) 0; cellnum < 50; cellnum += 2)
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{
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// create a numeric cell
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c = r.createCell(cellnum);
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// do some goofy math to demonstrate decimals
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c.setCellValue(rownum * 10000 + cellnum
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+ (((double) rownum / 1000)
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+ ((double) cellnum / 10000)));
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// on every other row
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if ((rownum % 2) == 0)
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{
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// set this cell to the first cell style we defined
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c.setCellStyle(cs);
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}
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// create a string cell (see why += 2 in the
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c = r.createCell((short) (cellnum + 1));
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// set the cell's string value to "TEST"
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c.setCellValue("TEST");
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// make this column a bit wider
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s.setColumnWidth((short) (cellnum + 1), (short) ((50 * 8) / ((double) 1 / 20)));
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// on every other row
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if ((rownum % 2) == 0)
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{
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// set this to the white on red cell style
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// we defined above
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c.setCellStyle(cs2);
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}
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}
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}
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//draw a thick black border on the row at the bottom using BLANKS
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// advance 2 rows
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rownum++;
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rownum++;
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r = s.createRow(rownum);
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// define the third style to be the default
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// except with a thick black border at the bottom
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cs3.setBorderBottom(cs3.BORDER_THICK);
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//create 50 cells
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for (short cellnum = (short) 0; cellnum < 50; cellnum++)
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{
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//create a blank type cell (no value)
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c = r.createCell(cellnum);
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// set it to the thick black border style
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c.setCellStyle(cs3);
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}
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//end draw thick black border
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// demonstrate adding/naming and deleting a sheet
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// create a sheet, set its title then delete it
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s = wb.createSheet();
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wb.setSheetName(1, "DeletedSheet");
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wb.removeSheetAt(1);
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//end deleted sheet
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// write the workbook to the output stream
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// close our file (don't blow out our file handles
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wb.write(out);
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out.close();
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]]></source>
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</section>
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<section title="Reading or modifying an existing file">
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<p>Reading in a file is equally simple. To read in a file, create a
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new instance of org.apache.poi.poifs.Filesystem, passing in an open InputStream, such as a FileInputStream
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for your XLS, to the constructor. Construct a new instance of
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org.apache.poi.hssf.usermodel.HSSFWorkbook passing the
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Filesystem instance to the constructor. From there you have access to
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all of the high level model objects through their assessor methods
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(workbook.getSheet(sheetNum), sheet.getRow(rownum), etc).
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</p>
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<p>Modifying the file you have read in is simple. You retrieve the
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object via an assessor method, remove it via a parent object's remove
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method (sheet.removeRow(hssfrow)) and create objects just as you
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would if creating a new xls. When you are done modifying cells just
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call workbook.write(outputstream) just as you did above.</p>
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<p>An example of this can be seen in
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<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>
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</section>
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</section>
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<section title="Event API">
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<p>The event API is brand new. It is intended for intermediate
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developers who are willing to learn a little bit of the low level API
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structures. Its relatively simple to use, but requires a basic
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understanding of the parts of an Excel file (or willingness to
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learn). The advantage provided is that you can read an XLS with a
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relatively small memory footprint.
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</p>
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<p>To use this API you construct an instance of
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org.apache.poi.hssf.eventmodel.HSSFRequest. Register a class you
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create that supports the
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org.apache.poi.hssf.eventmodel.HSSFListener interface using the
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HSSFRequest.addListener(yourlistener, recordsid). The recordsid
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should be a static reference number (such as BOFRecord.sid) contained
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in the classes in org.apache.poi.hssf.record. The trick is you
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have to know what these records are. Alternatively you can call
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HSSFRequest.addListenerForAllRecords(mylistener). In order to learn
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about these records you can either read all of the javadoc in the
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org.apache.poi.hssf.record package or you can just hack up a
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copy of org.apache.poi.hssf.dev.EFHSSF and adapt it to your
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needs. TODO: better documentation on records.</p>
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<p>Once you've registered your listeners in the HSSFRequest object
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you can construct an instance of
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org.apache.poi.poifs.filesystem.FileSystem (see POIFS howto) and
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pass it your XLS file inputstream. You can either pass this, along
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with the request you constructed, to an instance of HSSFEventFactory
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via the HSSFEventFactory.processWorkbookEvents(request, Filesystem)
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method, or you can get an instance of DocumentInputStream from
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Filesystem.createDocumentInputStream("Workbook") and pass
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it to HSSFEventFactory.processEvents(request, inputStream). Once you
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make this call, the listeners that you constructed receive calls to
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their processRecord(Record) methods with each Record they are
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registered to listen for until the file has been completely read.
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</p>
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<p>A code excerpt from org.apache.poi.hssf.dev.EFHSSF (which is
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in CVS or the source distribution) is reprinted below with excessive
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comments:</p>
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<source><![CDATA[
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/**
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* This example shows how to use the event API for reading a file.
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*/
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public class EventExample
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implements HSSFListener
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{
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private SSTRecord sstrec;
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/**
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* This method listens for incoming records and handles them as required.
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* @param record The record that was found while reading.
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*/
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public void processRecord(Record record)
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{
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switch (record.getSid())
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{
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// the BOFRecord can represent either the beginning of a sheet or the workbook
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case BOFRecord.sid:
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BOFRecord bof = (BOFRecord) record;
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if (bof.getType() == bof.TYPE_WORKBOOK)
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{
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System.out.println("Encountered workbook");
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// assigned to the class level member
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} else if (bof.getType() == bof.TYPE_WORKSHEET)
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{
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System.out.println("Encountered sheet reference");
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}
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break;
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case BoundSheetRecord.sid:
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BoundSheetRecord bsr = (BoundSheetRecord) record;
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System.out.println("New sheet named: " + bsr.getSheetname());
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break;
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case RowRecord.sid:
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RowRecord rowrec = (RowRecord) record;
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System.out.println("Row found, first column at "
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+ rowrec.getFirstCol() + " last column at " + rowrec.getLastCol());
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break;
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case NumberRecord.sid:
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NumberRecord numrec = (NumberRecord) record;
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System.out.println("Cell found with value " + numrec.getValue()
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+ " at row " + numrec.getRow() + " and column " + numrec.getColumn());
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break;
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// SSTRecords store a array of unique strings used in Excel.
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case SSTRecord.sid:
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sstrec = (SSTRecord) record;
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for (int k = 0; k < sstrec.getNumUniqueStrings(); k++)
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{
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System.out.println("String table value " + k + " = " + sstrec.getString(k));
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}
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break;
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case LabelSSTRecord.sid:
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LabelSSTRecord lrec = (LabelSSTRecord) record;
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System.out.println("String cell found with value "
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+ sstrec.getString(lrec.getSSTIndex()));
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break;
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}
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}
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/**
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* Read an excel file and spit out what we find.
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*
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* @param args Expect one argument that is the file to read.
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* @throws IOException When there is an error processing the file.
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*/
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public static void main(String[] args) throws IOException
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{
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// create a new file input stream with the input file specified
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// at the command line
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FileInputStream fin = new FileInputStream(args[0]);
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// create a new org.apache.poi.poifs.filesystem.Filesystem
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POIFSFileSystem poifs = new POIFSFileSystem(fin);
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// get the Workbook (excel part) stream in a InputStream
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InputStream din = poifs.createDocumentInputStream("Workbook");
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// construct out HSSFRequest object
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HSSFRequest req = new HSSFRequest();
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// lazy listen for ALL records with the listener shown above
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req.addListenerForAllRecords(new EventExample());
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// create our event factory
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HSSFEventFactory factory = new HSSFEventFactory();
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// process our events based on the document input stream
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factory.processEvents(req, din);
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// once all the events are processed close our file input stream
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fin.close();
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// and our document input stream (don't want to leak these!)
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din.close();
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System.out.println("done.");
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}
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}
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]]></source>
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</section>
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<section title="Low Level APIs">
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<p>The low level API is not much to look at. It consists of lots of
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"Records" in the org.apache.poi.hssf.record.* package,
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and set of helper classes in org.apache.poi.hssf.model.*. The
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record classes are consistent with the low level binary structures
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inside a BIFF8 file (which is embedded in a POIFS file system). You
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probably need the book: "Microsoft Excel 97 Developer's Kit"
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from Microsoft Press in order to understand how these fit together
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(out of print but easily obtainable from Amazon's used books). In
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order to gain a good understanding of how to use the low level APIs
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should view the source in org.apache.poi.hssf.usermodel.* and
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the classes in org.apache.poi.hssf.model.*. You should read the
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documentation for the POIFS libraries as well.</p>
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</section>
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<section title="HSSF Class/Test Application">
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<p>The HSSF application is nothing more than a test for the high
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level API (and indirectly the low level support). The main body of
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its code is repeated above. To run it:
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</p>
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<ul>
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<li>download the poi-alpha build and untar it (tar xvzf
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tarball.tar.gz)
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</li>
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<li>set up your classpath as follows:
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<code>export HSSFDIR={wherever you put HSSF's jar files}
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export LOG4JDIR={wherever you put LOG4J's jar files}
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export CLASSPATH=$CLASSPATH:$HSSFDIR/hssf.jar:$HSSFDIR/poi-poifs.jar:$HSSFDIR/poi-util.jar:$LOG4JDIR/jog4j.jar</code>
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</li><li>type:
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<code>java org.apache.poi.hssf.dev.HSSF ~/myxls.xls write</code></li>
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</ul>
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<p></p>
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<p>This should generate a test sheet in your home directory called <code>"myxls.xls"</code>. </p>
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<ul>
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<li>Type:
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<code>java org.apache.poi.hssf.dev.HSSF ~/input.xls output.xls</code>
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<br/>
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<br/>
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This is the read/write/modify test. It reads in the spreadsheet, modifies a cell, and writes it back out.
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Failing this test is not necessarily a bad thing. If HSSF tries to modify a non-existant sheet then this will
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most likely fail. No big deal. </li>
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</ul>
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</section>
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<section title="HSSF Logging Facility">
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<p>
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POI has a small amount of logging code embedded within it. Defining the system property
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poi.logging will enable logging to standard out.
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</p>
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</section>
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<section title="HSSF Developer's Tools">
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<p>HSSF has a number of tools useful for developers to debug/develop
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stuff using HSSF (and more generally XLS files). We've already
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discussed the app for testing HSSF read/write/modify capabilities;
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now we'll talk a bit about BiffViewer. Early on in the development of
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HSSF, it was decided that knowing what was in a record, what was
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wrong with it, etc. was virtually impossible with the available
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tools. So we developed BiffViewer. You can find it at
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org.apache.poi.hssf.dev.BiffViewer. It performs two basic
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functions and a derivative.
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</p>
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<p>The first is "biffview". To do this you run it (assumes
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you have everything setup in your classpath and that you know what
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you're doing enough to be thinking about this) with an xls file as a
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parameter. It will give you a listing of all understood records with
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their data and a list of not-yet-understood records with no data
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(because it doesn't know how to interpret them). This listing is
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useful for several things. First, you can look at the values and SEE
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what is wrong in quasi-English. Second, you can send the output to a
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file and compare it.
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</p>
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<p>The second function is "big freakin dump", just pass a
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file and a second argument matching "bfd" exactly. This
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will just make a big hexdump of the file.
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</p>
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<p>Lastly, there is "mixed" mode which does the same as
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regular biffview, only it includes hex dumps of certain records
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intertwined. To use that just pass a file with a second argument
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matching "on" exactly.</p>
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<p>In the next release cycle we'll also have something called a
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FormulaViewer. The class is already there, but its not very useful
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yet. When it does something, we'll document it.</p>
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</section>
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<section title="What's Next?">
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<p>This release contains code that supports "internationalization"
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or more accurately non-US/UK languages; however, it has not been
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tested with the new API changes (please help us with this). We've
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shifted focus a bit for this release in recognition of the
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international support we've gotten. We're going to focus on western
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European languages for our first beta. We're more than happy to
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accept help in supporting non-Western European languages if someone
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who knows what they're doing in this area is willing to pitch in!
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(There is next to no documentation on what is necessary to support
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such a move and its really hard to support a language when you don't even
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know the alphabet).</p>
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<p>This release of HSSF does not yet support Formulas. I've been
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focusing on the requests I've gotten in. That being said, if we get
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more user feedback on what is most useful first we'll aim for that.
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As a general principal, HSSF's goal is to support HSSF-Serializer
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(meaning an emphasis on write). We would like to hear from you! How
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are you using HSSF/POIFS? How would you like to use it? What features
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are most important first?
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</p>
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</section>
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</section>
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</section>
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</body>
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</document>
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