I am using apache poi api to deal with my spread sheet files.
I have observed, if we try to edit an existing .xls file it size is not the same as if that same file (same data ) is written in one go.
It is normal for an Excel spreadsheet to grow after being opened or edited. When a spreadsheet is opened in Microsoft Excel the formulas are automatically calculated, so this increases the size of the file. If a spreadsheet is opened by Apache POI it is up to the developer to call the (FormulaEvaluator) to update all the values. When a spreadsheet is read by Apache POI and the formulas have not been evaluated, formula answers may be invalid.
POI will always write out one record per cell
Excel, however, will sometimes bunch several similar sequential cells up into a single record. For example, if you have 3 cells in a row that are blank but styled, then excel will generate a MulBlankRecord which holds all of them. For several cells in a row with simple numbers in them, excel uses a MulRKRecord
When POI reads in a file, it expands all the Mul* records out. At write time, the individual cell records are written, so the file gets slightly bigger. I think there's an entry in the POI bugzilla for the enhancement to get POI to coalesce cells into Mul records, but no-one seems to have volunteered to work on it yet...
Related
I am filling cells of an Excel file using Apache POI, and there are a lot of formula cells in the document. However, their values are not refreshed when I open the document in Excel.
It's my understanding that I need to use a FormulaEvaluator to refresh formula cells. Is there a way, though, to update all formula cells at once? There are a lot of them, and while making an exhaustive list is not out of question, it's certainly not something I'm very willing to do.
Sure. Refreshing all the formulas in a workbook is possibly the more typical use case anyway.
If you're using HSSF, call evaluatorAllFormulaCells:
HSSFFormulaEvaluator.evaluateAllFormulaCells(hssfWorkbook)
If you're using XSSF, call evaluatorAllFormulaCells:
XSSFFormulaEvaluator.evaluateAllFormulaCells(xssfWorkbook)
More details are available on the poi website
wb.setForceFormulaRecalculation(true);
// replace "wb" with your HSSFWorkbook/XSSFWorkbook object
https://poi.apache.org/apidocs/org/apache/poi/hssf/usermodel/HSSFWorkbook.html#setForceFormulaRecalculation-boolean-
https://poi.apache.org/apidocs/org/apache/poi/xssf/usermodel/XSSFWorkbook.html#setForceFormulaRecalculation-boolean-
I'm working on a excel workbook, using Java POI.
I have several sheets and I need to add Pagination to 4 of them.
The problem is :
How I am suppose to attribute a global pagination to these sheets ?
sheet.getFooter().setRight(HeaderFooter.page()); only works for ONE sheet.
Cordially.
The Excel file format mandates that a footer is always per sheet, even in Excel itself you have to set up the footer for each sheet separately as far as I know. So the Apache POI API reflects this and you need to set the footer for each sheet.
Naturally you can write a helper function where you pass in the Sheet object to not have to code it 4 times here.
I have made an excel sheet which is generated by Java. The cells can only accept certain values, depending on data validation done against lists on a separate sheet.
This all works great, but if a user copies some values from another cell and pastes it into the cell it avoids validation... is there any way to prevent this?
You can do this by setting data format for that cell.
style = wb.createCellStyle();
style.setDataFormat(wb.createDataFormat().getFormat("0.000%"));
which will percentage value.
For documentation goto:
Apache HSSF Doc
I have one question. Is there any API that can process xlsx and xls file. The requirement is i have one excel file. i have to encrypt values of some specific columns. without affecting the format of cell like cell color, cell formula, cell date format, cell currency format, charts etc. I have used APACHE POI library. i did not get success. it is very slow and not working on large file. i also searched on google but i dint get proper result.
An alternative to POI is JXL.
We used it successfully with rather large files.
I am designing stock market predictor wherein the user is supposed to update his database of historical indexes through the web. I want to just add the new data to the TOP of my excel file. not Bottom but on Top of my file. Now i know i can make a copy and modify that copy and the regular stuff.
How to do i avoid this complicated steps and do in few steps instead?
is it possible to do this without making a copy
Apache POI's Sheet objects have a shiftRows method you could use to do this. Here's an example from the Busy Developers' Guide to HSSF and XSSF Features:
Shift rows up or down on a sheet
shiftRows API documentation
Here's an answer with some sample code:
How to create new rows in apache poi 3.6?
Why not update a .csv (which is easier) and at the end after all updates are done, convert it to .xls