Apache POI SXSSF - Workbook.close() 清除先前保存的文件中的第二个（最后一个）工作表数据

Question

I'm trying to modify existing document and fill large amount (~ 1 million rows) of data to a new sheet. I use SXSSF (Streaming Usermodel API) for this purpose. When I call workbook.close() it clears the added (the last) sheet data but still adds a new empty sheet. Did I miss something in code? Thanks a lot for the answers. Example with 1000 rows only:

package com.company.excel;

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.streaming.SXSSFWorkbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public class TestPoiStreaming {
   public static void main(String[] args) throws IOException {
      int rowNumber = 0;
      int cellNumber = 0;
      String outputFileName = "c:/temp/test1.xlsx";
      File outFile = new File(outputFileName);
      Workbook workbook = new SXSSFWorkbook(100);
      try {
         Sheet sheet = workbook.createSheet("Sheet1");
         Row row = null;
         for (int i = 0; i < 1000; i++) {
            row = sheet.createRow(rowNumber++);
            cellNumber = 0;
            for (int j = 1; j <= 10; j++) {
               Cell cell = row.createCell(cellNumber++);
               cell.setCellValue(String.valueOf(j));
            }
         }
         try (FileOutputStream out = new FileOutputStream(outFile)) {
            workbook.write(out);
         }
      } finally {
         workbook.close();
         ((SXSSFWorkbook) workbook).dispose();
      }

      rowNumber = 0;
      cellNumber = 0;
      workbook = new SXSSFWorkbook((XSSFWorkbook) WorkbookFactory.create(outFile), 100);
      try {
         Sheet sheet = workbook.createSheet("Sheet2");
         Row row = null;
         for (int i = 0; i < 1000; i++) {
            row = sheet.createRow(rowNumber++);
            cellNumber = 0;
            for (int j = 1; j <= 10; j++) {
               Cell cell = row.createCell(cellNumber++);
               cell.setCellValue(String.valueOf(j));
            }
         }
         Files.delete(Paths.get(outFile.getPath()));
         try (FileOutputStream out = new FileOutputStream(outFile)) {
            workbook.write(out);
         }
      } finally {
         workbook.close();
         ((SXSSFWorkbook) workbook).dispose();
      }
   }
}

Answer 1

You did not reset rowNumber to zero in the second block. The sheet "Sheet2" is not empty. Simply scroll down to line 1001 and you will see the contents.

Answer for the edited code: I had problems executing it before you were reading the same file several times and also trying to delete it at the same time. Why don't you just try reading and writing once, instead of writing the first sheet and then reopening in order to add the second? Here is the full code with several lines deleted:

public static void main(String[] args) throws IOException, InvalidFormatException {
    int rowNumber = 0;
    int cellNumber = 0;
    String outputFileName = "c:/temp/test1.xlsx";
    File outFile = new File(outputFileName);
    Workbook workbook = new SXSSFWorkbook(100);
    Sheet sheet = workbook.createSheet("Sheet1");
    Row row = null;
    for (int i = 0; i < 1000; i++) {
      row = sheet.createRow(rowNumber++);
      cellNumber = 0;
      for (int j = 1; j <= 10; j++) {
        Cell cell = row.createCell(cellNumber++);
        cell.setCellValue(String.valueOf(j));
      }
    }
    rowNumber = 0;
    cellNumber = 0;
    try {
      sheet = workbook.createSheet("Sheet2");
      row = null;
      for (int i = 0; i < 1000; i++) {
        row = sheet.createRow(rowNumber++);
        cellNumber = 0;
        for (int j = 1; j <= 10; j++) {
          Cell cell = row.createCell(cellNumber++);
          cell.setCellValue(String.valueOf(j));
        }
      }
      try (FileOutputStream out = new FileOutputStream(outFile)) {
        workbook.write(out);
      }
    } finally {
      workbook.close();
      ((SXSSFWorkbook) workbook).dispose();
    }
  }