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Apache POI not "Saving" excel file

I am writing a small utility that creates a pivot table in an excel sheet using POI and I want to read the data from the pivot table back to the program which will save it as a PDF file using Itext. I am running into a problem where the program cannot read the data from the pivot table after it is created. The program only can "see" the information in the pivot table after I manually open the created file and hit the save button in excel. Does anyone know a way to read the data from the pivot table from the XSSFPivotTable object or otherwise force a way for the file to "save" so it can be accessed by the program again?
Here is a snippet of code so you can see what I'm talking about. I'm a student so any advice on best practices would be greatly appreciated as well.
public void returnPivotData() throws IOException {
FileInputStream fs = new FileInputStream(this.xlsxFile);
XSSFWorkbook book = new XSSFWorkbook(fs);
XSSFSheet dataSheet = book.getSheet("Sheet1");
AreaReference dataRef = new AreaReference("A1:E15",
SpreadsheetVersion.EXCEL2007);
XSSFPivotTable table = dataSheet.createPivotTable(dataRef,
new CellReference("A16"));
table.addRowLabel(0);
table.addColumnLabel(DataConsolidateFunction.SUM, 3);
// Save the data back to the file
FileOutputStream fsOut = new FileOutputStream(
"D:\\workspace\\test.xlsx");
book.write(fsOut);
fsOut.close();
book.close();
fs.close();
// This does not allow access
FileInputStream fsIn = new FileInputStream("D:\\workspace\\test.xlsx");
XSSFWorkbook bookNew = new XSSFWorkbook(fsIn);
XSSFSheet sheet = bookNew.getSheet("Sheet1");
for (int i = 0; i < 20; i++) {
XSSFRow rowNew = sheet.getRow(i);
XSSFCell cellNew = rowNew.getCell(0,
MissingCellPolicy.CREATE_NULL_AS_BLANK);
System.out.println(cellNew.toString());
}
fsIn.close();
bookNew.close();
}

Apache POI can't format filled cells as numeric

I am trying to change CellTypes of already filled Cells in Apache POI, but I keep getting an IllegalStateException. The problem should be reproduceable using POI(-ooxml) 3.16.
public static void main(String[] args) throws Exception
{
//Setting up the workbook and the sheet
XSSFWorkbook wb = new XSSFWorkbook();
XSSFSheet s = wb.createSheet();
//Setting up the CTTable
XSSFTable t = s.createTable();
CTTable ctt = t.getCTTable();
ctt.setId(1);
ctt.setName("CT Table Test");
ctt.setRef("A1:B2");
CTTableColumns cttcs = ctt.addNewTableColumns();
CTTableColumn cttc1 = cttcs.addNewTableColumn();
cttc1.setId(1);
CTTableColumn cttc2 = cttcs.addNewTableColumn();
cttc2.setId(2);
//Creating the cells
XSSFCell c1 = s.createRow(0).createCell(0);
XSSFCell c2 = s.getRow(0).createCell(1);
XSSFCell c3 = s.createRow(1).createCell(0);
XSSFCell c4 = s.getRow(1).createCell(1);
//Inserting values; some numeric strings, some alphabetical strings
c1.setCellValue(/*12*/"12"); //Numbers have to be inputted as a string
c2.setCellValue(/*34*/"34"); //for the code to work
c3.setCellValue("AB");
c4.setCellValue("CD");
//With those lines, the code would also crash
//c1.setCellType(CellType.NUMERIC);
//c2.setCellType(CellType.NUMERIC);
//On write() it produces a "java.lang.IllegalStateException: Cannot get a STRING value from a NUMERIC cell"
FileOutputStream fos = new FileOutputStream("test.xlsx");
wb.write(fos);
fos.flush();
fos.close();
wb.close();
}
Also, when not setting any CellValue for c1 and c2, you can actually set their CellType to NUMERIC and suddenly the code works again. It also works without the CTTable.
Any ideas or workarounds? Or is it a bug of POI (since it tries fetching a string value from any Cell regardless of its CellType)?

You need to use Apache POI 3.17 beta 1 or later for this to work (or a nightly build from after 20170607)
If you do, you can also make your code significantly simpler and cleaner too. As shown in the testNumericCellsInTable() unit test, your code could simplify to something like:
Workbook wb = new XSSFWorkbook();
Sheet s = wb.createSheet();
// Create some cells, some numeric, some not
Cell c1 = s.createRow(0).createCell(0);
Cell c2 = s.getRow(0).createCell(1);
Cell c3 = s.getRow(0).createCell(2);
Cell c4 = s.createRow(1).createCell(0);
Cell c5 = s.getRow(1).createCell(1);
Cell c6 = s.getRow(1).createCell(2);
c1.setCellValue(12);
c2.setCellValue(34.56);
c3.setCellValue("ABCD");
c4.setCellValue("AB");
c5.setCellValue("CD");
c6.setCellValue("EF");
// Setting up the CTTable
Table t = s.createTable();
t.setName("TableTest");
t.setDisplayName("CT_Table_Test");
t.addColumn();
t.addColumn();
t.addColumn();
t.setCellReferences(new AreaReference(
new CellReference(c1), new CellReference(c6)
));
(Unlike your problem code, this does a mixture of integers, floating point numbers and strings for the table headers, to show the various options)

Apache POI setCellData not actually setting cell data

Using Apache POI 3.16
Eclipse IDE neon 3
Selenium 3.4 (not that it matters in this case)
I'm having an issue with writing values to an excel spreadsheet then reading back the value.
Here's what I want to do at a high level:
Open up an excel file
write to row 1 column 1 (we are using index starting at 0)
Read back what was written in that cell.
The cell contains the value "B2". In a setCellData() function, I write to the cell a "Hello World" and have the function return the contents of the cell. I also have a separate function that reads in the contents of a specified cell.
When I run the following code:
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
public class Udemy_Excel_Driven {
public static XSSFWorkbook wb;
public static XSSFSheet sheet;
public static XSSFRow row;
public static XSSFCell cell;
public static FileInputStream fis;
public static void main(String[] args) throws IOException, Exception
{
System.out.println("Before cell edit value is:");
System.out.println(getCellData(1,1));
String value = setCellData(1,1,"Hello World");
System.out.println("What's the value after setting it with setCellData()?");
System.out.println(value);
System.out.println("What's the value using getCellData()?");
System.out.println(getCellData(1,1));
}
public static String getCellData(int rowNum, int colNum) throws IOException
{
/*
* Hierarchy of excel data:
*
* Workbook - take control of this
* Sheet - pick up the sheet of the workbook
* Row - pick the row
* Column - after picking the row, select the column
* Value - grab the value from the cell
*
*/
//0. = identify the path to the excel file in the system.
fis = new FileInputStream("C:\\data.xlsx");
//1. Create a new XSSFWorkbook object. You need to pass in a FileInputStream object into it, which you created earlier.
wb = new XSSFWorkbook(fis);
//2. Get the sheet in the workbook. Create a new XSSFsheet object and set it to the sheet in the workbook
// Access the workbook method "getSheet" and pass in the name of the sheet
sheet = wb.getSheet("script");
//3. Get the row and column. We are going to access the data from row 2 column 2. And remember the indices start at 0.
row = sheet.getRow(rowNum);
cell = row.getCell(colNum);
//get the value specified in the row and cell
return cell.getStringCellValue();
}
public static String setCellData(int rowNum, int colNum, String data) throws IOException
{
fis = new FileInputStream("C:\\data.xlsx");
wb = new XSSFWorkbook(fis);
sheet = wb.getSheet("script");
row = sheet.getRow(rowNum);
cell = row.getCell(colNum);
cell.setCellValue(data);
String cellData = cell.getStringCellValue();
return cellData;
}
I get the following output:
Before cell edit value is:
B2
What's the value after setting it with setCellData()?
Hello World
What's the value using getCellData()?
B2
I don't think the write actually occurred since I opened up the excel file and the "Hello World" string wasn't in the specified cell. Any answers to this issue?

I don't see any part of your code that actually writes to your file.
It should more or less look something like this:
FileOutputStream fileOut = new FileOutputStream("C:\\data.xlsx");
wb.write(fileOut);
fileOut.close();
You can also consult this guide for this issue as well as other functionality that you might be interested in implementing.

convert xls to image

I am trying to create multiple and complex Table in PPT (not PPTX), si Im using POI Apache HSLF, The problem is that I have multiple kinds of tables with multiple headers sometimes,
I think then to create my tables on xls files than convert them to image and finally embed them on my generated PPT
I know it is a complex theory, but what I need now is to transform my XLS to image
any help please
Thanks

You cant do it with POI but You can convert or copy charts(graphs) using J XL or Aspose Cells(Aspose is not free).
This is the code snippet to extract excel chart to image
public class ExportChartToImage
{
public static void main(String[] args) throws Exception
{
//Start Excel
Application excelApp = new Application();
excelApp.setVisible(true);
//Create test workbook
Workbook workbook = excelApp.createWorkbook("/home/tejus/Desktop/Chart Test");
//Get the first (and the only) worksheet
final Worksheet worksheet1 = workbook.getWorksheet(1);
//Fill-in the first worksheet with sample data
worksheet1.getCell("A1").setValue("Date");
worksheet1.getCell("A2").setValue("March 1");
worksheet1.getCell("A3").setValue("March 8");
worksheet1.getCell("A4").setValue("March 15");
worksheet1.getCell("B1").setValue("Customer");
worksheet1.getCell("B2").setValue("Smith");
worksheet1.getCell("B3").setValue("Jones");
worksheet1.getCell("B4").setValue("James");
worksheet1.getCell("C1").setValue("Sales");
worksheet1.getCell("C2").setValue("23");
worksheet1.getCell("C3").setValue("17");
worksheet1.getCell("C4").setValue("39");
excelApp.getOleMessageLoop().doInvokeAndWait(new Runnable()
{
public void run()
{
final Variant unspecified = Variant.createUnspecifiedParameter();
final Int32 localeID = new Int32(LocaleID.LOCALE_SYSTEM_DEFAULT);
Range sourceDataNativePeer = worksheet1.getRange("A1:C4").getPeer();
_Worksheet worksheetNativePeer = worksheet1.getPeer();
IDispatch chartObjectDispatch = worksheetNativePeer.chartObjects(unspecified, localeID);
ChartObjectsImpl chartObjects = new ChartObjectsImpl(chartObjectDispatch);
ChartObject chartObject = chartObjects.add(new DoubleFloat(100), new DoubleFloat(150), new DoubleFloat(300), new DoubleFloat(225));
_Chart chart = chartObject.getChart();
chart.setSourceData(sourceDataNativePeer, new Variant(XlRowCol.xlRows));
BStr fileName = new BStr("/home/tejus/Desktop/chart.gif");
Variant filterName = new Variant("gif");
Variant interactive = new Variant(false);
chart.export(fileName, filterName, interactive);
chart.setAutoDelete(false);
chart.release();
chartObject.setAutoDelete(false);
chartObject.release();
chartObjects.setAutoDelete(false);
chartObjects.release();
chartObjectDispatch.setAutoDelete(false);
chartObjectDispatch.release();
}
});
System.out.println("Press 'Enter' to terminate the application");
System.in.read();
//Close the MS Excel application.
boolean saveChanges = false;
workbook.close(saveChanges);
boolean forceQuit = true;
excelApp.close(forceQuit);
}
}
i used J excel

There are 3rd party products like aspose which provides API's for converting worksheets to image file. However you could start by creating a rendering engine which does the geometry layout and write all the data that are available on the sheet to a canvas and then create a converter which gets the pixel data from the canvas and renders to a file.

Modifying existing excel using jxl

I m not able to edit the existing excel sheet using jxl.
It always creates a new one.
Can anyone please help me out with it.
Please give a small sample code.

jxl is designed for increased read efficiency (since this is the primary use of the API). In order to improve performance, data which relates to output information (eg. all the formatting information such as fonts) is not interpreted when the spreadsheet is read, since this is superfluous when interrogating the raw data values.
However, if we need to modify this spreadsheet a handle to the various write interfaces is needed, which can be obtained using the copy method.
Workbook workbook = Workbook.getWorkbook(new File("myfile.xls"));
WritableWorkbook copy = Workbook.createWorkbook(new File("temp.xls"), workbook);
This copies the information that has already been read in as well as performing the additional processing to interpret the fields that are necessary to for writing spreadsheets. The disadvantage of this read-optimized strategy is that we have two spreadsheets held in memory rather than just one, thus doubling the memory requirements.
But after this, you can do whatever you want. Like:
WritableSheet sheet2 = copy.getSheet(1);
WritableCell cell = sheet2.getWritableCell(1, 2);
if (cell.getType() == CellType.LABEL)
{
Label l = (Label) cell;
l.setString("modified cell");
}
copy.write();
copy.close();
workbook.close();
Note: this is directly taken from Andy Khan's tutorial page.

I know that this is quite an old question, but if anyone will encounter the same problem, then to preserve the correct formatting (font type, colouring, etc. )
you should save the cell format before casting it to Label, and then force the cell to the previous formatting.
Code:
CellFormat cfm = cell.getCellFormat();
Label l = (Label) cell;
l.setString("modified cell");
cell.setCellFormat(cfm);

//there is god example of it, you can copy in ur project and check it out, to
//understand how it works
Workbook wk = Workbook.getWorkbook(new File("ex.xls"));
//
WritableWorkbook wkr = Workbook.createWorkbook(new File("modifed.xls"), wk);
/* second line makes copy of wk excel file object /creates a readable spreadsheet.
both are now similar and i can Modify exiting wkr spreadsheets */
//next 2 line retrieve sheet number 0 and cell (1,1)
WritableSheet getsht = wkr.getSheet(0);
WritableCell getcl = getsht.getWritableCell(1, 1);
//making own font
WritableFont ft = new WritableFont(WritableFont.ARIAL, 20 , WritableFont.BOLD, true , UnderlineStyle.SINGLE);
//making Format, which uses font
WritableCellFormat form = new WritableCellFormat( ft);
Number nb = ( Number ) getcl ;
nb.setCellFormat( form );
wkr.write();
wkr.close();

I personally use this code to append the xls file and create one if it doesn't exist.
Using jxl 2.6:
public class Excel {
private String fileName = "excel_file.xls";
private String sheetName = "sheet1";
private WritableWorkbook writableWorkbook;
private int rowCount;
private Workbook wb;
// assigns checks if file exists or not, both cases we assign it to a WritableWorkbook // object so that we can write to it.
private void assignWorkBook() throws IOException, BiffException {
// File f = new File(System.getProperty("user.dir") +"\\"+fileName);
File inp = new File(fileName);
try{
wb = Workbook.getWorkbook(inp);
writableWorkbook = Workbook.createWorkbook(inp, wb);
} catch (FileNotFoundException e){
writableWorkbook = Workbook.createWorkbook(inp); //Create a new one
}
}
public int getRowCount() {
return rowCount;
}
// this function writes a vector to an excel file, checks if there is already a sheet
// with that name or not, and uses it. then we have to close the Workbook object before
// we could write to the file, and then we save the file.
// That is, the file is always saved after writing to it.
public void writeRow(Vector<String> playerVector) throws WriteException, IOException, BiffException {
assignWorkBook();
WritableSheet excelSheet;
if(writableWorkbook.getNumberOfSheets() == 0) {
excelSheet = writableWorkbook.createSheet(sheetName, 0);
}
else {
excelSheet = writableWorkbook.getSheet(sheetName);
}
rowCount = excelSheet.getRows();
int colCount = 0;
for(String playerStat:playerVector) {
Label label = new Label(colCount++, rowCount, playerStat);
excelSheet.addCell(label);
}
if(wb != null) {
wb.close();
}
writableWorkbook.write();
writableWorkbook.close(); //everytime save it.
}
}