Develop Reference

How to add columns to an existing large excel file using SXSSF Apache POI?

I am working with a large excel file ( larger than 40 Mb , more than 100k rows and 50 columns ). I am successfully reading it using POI ( 3.10.1 version ) event stream and then doing some calculation and storing result into a List.
Now I have to append this List as a column in the same file. In this part I am facing issue.
I have tried to achieve this by using the below code
FileInputStream excelFile = new FileInputStream(new File(pathToFile));
Workbook workbook = new XSSFWorkbook(excelFile);
Sheet datatypeSheet = workbook.getSheetAt(0); // Get first sheet
Iterator<Row> iterator = datatypeSheet.iterator();
int i=0;
while (iterator.hasNext()) { // Loop over each row
Row currentRow = iterator.next();
Cell cell = currentRow.createCell(currentRow.getLastCellNum());
cell.setCellType(Cell.CELL_TYPE_STRING);
if(currentRow.getRowNum() == 0)
cell.setCellValue("OUTPUT-COLUMN"); // set column header for the new column
else {
cell.setCellValue(list.get(i)); // list contains the output to populate in new column
i++;
}
}
FileOutputStream fos = new FileOutputStream(new File(pathToOutput));
workbook.write(fos);
fos.close();
It is working fine with smaller files But the issue is that I am getting Out of memory for the larger files. Now I tried to modify this and use SXSSF in place of XSFF to get over the memory issue (See below code). But while testing even for smaller files I am getting output file same as the input file.
FileInputStream excelFile = new FileInputStream(new File(pathToFile));
XSSFWorkbook xwb = new XSSFWorkbook(inputStream);
inputStream.close();
SXSSFWorkbook wb = new SXSSFWorkbook(xwb,100);
wb.setCompressTempFiles(true);
SXSSFSheet sh = (SXSSFSheet) wb.getSheetAt(0);
Iterator<Row> iterator = datatypeSheet.iterator();
int i=0;
while (iterator.hasNext()) { // Loop over each row
Row currentRow = iterator.next();
Cell cell = currentRow.createCell(currentRow.getLastCellNum());
cell.setCellType(Cell.CELL_TYPE_STRING);
if(currentRow.getRowNum() == 0)
cell.setCellValue("OUTPUT-COLUMN"); // set column header for the new column
else {
cell.setCellValue(list.get(i)); // list contains the output to populate in new column
i++;
}
}
FileOutputStream fos = new FileOutputStream(new File(pathToOutput));
wb.write(fos);
fos.close();
Using a db is not suitable in my use case and i want to avoid using a temporary data structure to hold data for writing due to memory constraint.
Is there a way to write in output workbook while streaming ? Here is the code that I am using to read using POI Streaming API
private class ExcelData implements SheetContentsHandler {
LinkedHashMap<Strin, String> rowMap;
public void startRow(int rowNum) {
}
public void endRow(int rowNum) {
// Process the row
// Handle write to output workbook ??
}
public void cell(String cellReference, String formattedValue,
XSSFComment comment) {
// Save current row in rowMap ( column name => cell value )
}
public void headerFooter(String text, boolean isHeader, String tagName)
{
}
}

It is not possible to add column to existing workbook using POI SXSSF. It only allows addition of new rows.
The only solution is to read the existing workbook and write to a new workbook with the added column.
To achieve this we can store the rows in a data structure or database in the endrow() method and then use the persisted data to write a new workbook.

Issue while writing cells in excel file using apache POI

I am facing issue while writing the data to excel file.
I am using apache POI 4.1.2 version library.
Below is the sample code.
try {
outputStream = new FileOutputStream(EXCEL_FILE_PATH);
} catch (Exception e) {
System.out.println("Exception While writing excel file " + e.getMessage());
}
Workbook workbook = new HSSFWorkbook();
Sheet sheet = workbook.createSheet("FileCompare");
Row row = sheet.createRow(0);
Cell cellfilename = row.createCell(0);
cellfilename.setCellValue("File Name");
Cell cellfilename1 = row.createCell(1);
cellfilename1.setCellValue("Difference in File 1");
Cell cellfilenam2 = row.createCell(2);
cellfilenam2.setCellValue("Difference in File 2");
for (int diffcol = 1; diffcol < 3; diffcol++) {
for (int i = 1; i < 57; i++) {
Row rows = sheet.createRow(i);
// System.out.println("Difference Coln number " + diffcol);
Cell diffcell = rows.createCell(diffcol);
diffcell.setCellValue("abacds");
/*
* Cell diffcell2 = row.createCell(2); diffcell2.setCellValue("abacds");
*/
}
}
try {
workbook.write(outputStream);
} catch (Exception e) {
e.printStackTrace();
} finally {
outputStream.flush();
outputStream.close();
workbook.close();
}
In this only last column cells is getting saved in excel file , previous cells are kept as blank.
Kindly help and let me know if I am doing something wrong?

Not sure about the actual api but I think you inner loop should create columns and your outer one should create rows like this
for (int row=1:row<57;row++)
{
Row rows = sheet.createRow(row);
for (int diffCol = 1; diffCol < 3; difCol++)
{
Cell diffcell = rows.createCell(diffcol);
diffcell.setCellValue("abacds");
}
}

The problem is that inside your loop you're always using sheet.createRow(i) to retrieve the row you need, but as the docs says (docs that are written not so clear, actually) this method is always recreating a brand new & empty row, deleting the existing one (if a row at that i-position was already present).
It means that each iteration of yuor loop is actually deleting previous rows creating brand new rows: at the end only rows created by the last iteration are surviving!
To solve you're problem, use sheet.createRow(i) only one time in order to create the row at i-position and then only use sheet.getRow(i) to retreive it.
So replace (in your code) the following wrong line
Row rows = sheet.createRow(i);
with the following code
Row row = sheet.getRow(i);
if (row == null) row = sheet.createRow(i);
where new row is created only if it does not already exist!
And you're done, it works like a charm!

Java change cell content instead of creating new cells

I have a list of variables in an excel file which I use as input for an online app and generate a result. That occurs successfully however when I try to save the output in that same file by adding a new column and cells, the original content of the file would be deleted. I only want to add the info to the same document but the only option I found by googling is to create another file.
just to clarify:Variables for input
and instead of just adding the info this happens Changed document.
How can I fix it without adding more parameter and re-adding the info?
#Keyword
public void demoKey(String name) throws IOException{
FileInputStream fis = new FileInputStream("C://Users/i2srsm/Desktop/New Microsoft Excel Worksheet.xlsx");
XSSFWorkbook workbook = new XSSFWorkbook(fis);
XSSFSheet sheet = workbook.getSheet("Data for full set");
int columnNumber = sheet.getRow(0).getLastCellNum();
int firstRow = sheet.getFirstRowNum();
int lastRow = sheet.getLastRowNum();
sheet.createRow(firstRow).createCell(columnNumber).setCellValue('Proposta');
for (int rn=(firstRow); rn<=lastRow; rn++){
Cell cell = sheet.createRow(rn).createCell(columnNumber+1)
cell.setCellType(cell.CELL_TYPE_STRING);
cell.setCellValue(name);
FileOutputStream fos = new FileOutputStream("C://Users/i2srsm/Desktop/New Microsoft Excel Worksheet.xlsx");
workbook.write(fos);
fos.close();
}
}
}

don't use a sheet.createRow(row index) for update the existing excel file. this one create a new row. if you want to update the existing row in a sheet, firstly get related existing row and then create a new cell.
for get existing row
Row row = sheet.getRow(row index);
for create a new cell in above existing row
Cell cell = row.createCell(cell index);
try with this
sheet.getRow(firstRow).createCell(columnNumber).setCellValue("Proposta");
for (int i=(firstRow+1); i<=lastRow; i++){
Row row = sheet.getRow(i);
Cell cell = row.createCell(columnNumber);
cell.setCellType(cell.CELL_TYPE_STRING);
cell.setCellValue(name);
}
FileOutputStream fos = new FileOutputStream("C:/Users/LifeStyle/Documents/output.xlsx");
workbook.write(fos);
fos.close();

Not able to write to excel at run time using POI

I am trying to write my test results/data to excel at runtime for which I have written the below code. I am not getting any error while compiling this code however the results are not getting written in this. Can someone help me out with the problem?
public void WritetoExcel(String filepath, String OrderID) throws IOException
{
FileInputStream ExcelFile = new FileInputStream(filepath);
System.out.println(filepath);
ExcelWBook = new XSSFWorkbook(ExcelFile);
System.out.println("WorkBook Sucessfully");
ExcelWSheet = ExcelWBook.getSheetAt(0);
System.out.println("Sheet Sucessfully");
Iterator<Row> rowIterator= ExcelWSheet.iterator();
int RowNum =0;
while (rowIterator.hasNext())
{
Row row=rowIterator.next();
RowNum++;
}
try
{
Row = ExcelWSheet.createRow(RowNum);
Iterator<Cell> cellIterator=Row.iterator();
Cell = Row.getCell(0);
if (Cell==null)
{
Cell=Row.createCell(0);
Cell.setCellValue(OrderID);
}
else
{
Cell.setCellValue(OrderID);
}
FileOutputStream fileOut = new FileOutputStream(filepath);
ExcelWBook.write(fileOut);
fileOut.flush();
fileOut.close();
}
catch (Exception e )
{
throw (e);
}
}

I was going to make this a comment, but it is too long.
There are a few comments I can make about your code.
First, it seems you are iterating through and counting rows that exist in the sheet. Then you are creating a new row at that index. Since a spreadsheet could have missing rows, this will only work for a very specific type of spreadsheet. That is, one which has no missing rows, and you always want to add the next row in the next empty spot. Instead of:
Iterator<Row> rowIterator= ExcelWSheet.iterator();
int RowNum =0;
while (rowIterator.hasNext())
{
Row row=rowIterator.next();
RowNum++;
}
try
{
Row = ExcelWSheet.createRow(RowNum);
You can just as easily use:
int rowNum = ExcelWSheet.getLastRowNum() + 1;
Row row = ExcelWSheet.createRow(rowNum);
Then you write orderId in the first column of that row. Instead of:
Iterator<Cell> cellIterator=Row.iterator();
Cell = Row.getCell(0);
if (Cell==null)
{
Cell = Row.createCell(0);
Cell.setCellValue(OrderID);
}
else
{
Cell.setCellValue(OrderID);
}
You could just use:
Cell cell = row.createCell(0, MissingCellPolicy.CREATE_NULL_AS_BLANK);
cell.setCellValue(OrderID);
In addition, for this you don't even need the iterators, but when you really need to iterate through the rows and cells of a spreadsheet it is better to use the for each syntax like this:
for (Row row : sheet) {
for (Cell cell : row) {
// do something with the cell
}
}

Apache POI Pivot table error when same index is used for both column and row label

I am trying to create a pivot table to do cohort analysis
pivotTable.addColumnLabel(DataConsolidateFunction.COUNT, 1);
pivotTable.addRowLabel(1);
this is giving me an error while opening the file that the file is corrupt do you want to still open the file, when I say yes and open it, the result looks fine, the only issue is the error.
I did a workaround to have a duplicate column data with different name
for ex:
say column 1 is email added a duplicate column 36 with name dup email and did as shown below, it works fine
pivotTable.addColumnLabel(DataConsolidateFunction.COUNT, 1);
pivotTable.addRowLabel(35);
why in the first place it failed when I give both column and row label as 1.
Any help is greatly appreciated

If you set pivotTable.addRowLabel(1) using apache poi, then apache poi sets pivot field 1 only to be axisRow but it needs to be dataField too if you also want to pivotTable.addColumnLabel(DataConsolidateFunction.COUNT, 1). So we neeed to correct this.
Example:
import org.apache.poi.xssf.usermodel.*;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.*;
import java.io.*;
class PivotTableTest5 {
private static void setCellData(Sheet sheet) {
Row row = sheet.createRow(0);
Cell cell = row.createCell(0);
cell.setCellValue("Name");
cell = row.createCell(1);
cell.setCellValue("City");
for (int r = 1; r < 15; r++) {
row = sheet.createRow(r);
cell = row.createCell(0);
cell.setCellValue("Name " + ((r-1) % 4 + 1));
cell = row.createCell(1);
cell.setCellValue("City " + (int)((new java.util.Random().nextDouble() * 3)+1) );
}
}
public static void main(String[] args) {
try {
XSSFWorkbook wb = new XSSFWorkbook();
XSSFSheet sheet = wb.createSheet();
//Create some data to build the pivot table on
setCellData(sheet);
XSSFPivotTable pivotTable = sheet.createPivotTable(
new AreaReference(new CellReference("A1"), new CellReference("B15")), new CellReference("H5"));
//Count the second column. This needs to be second column a data field.
pivotTable.addColumnLabel(DataConsolidateFunction.COUNT, 1);
//Use second column as row label
pivotTable.addRowLabel(1);
//Apache poi sets pivot field 1 (second column) only to be axisRow but it needs to be dataField too.
pivotTable.getCTPivotTableDefinition().getPivotFields().getPivotFieldArray(1).setDataField(true);
FileOutputStream fileOut = new FileOutputStream("PivotTableTest5.xlsx");
wb.write(fileOut);
fileOut.close();
wb.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}