在Java Apache POI中更新現有的Excel文件

Question

我正在嘗試編寫一個每天運行的Java程序（使用任務調度程序），並且每次運行時都會在Excel電子表格中附加一列。 我遇到的問題是它只是重寫文件，而不是附加到它。 我正在使用Apache POI，這里是相關代碼：

 public static void toExcel(List<String> results, List<Integer> notActive)throws IOException{
    try {
        FileInputStream fIPS= new FileInputStream("test.xls"); //Read the spreadsheet that needs to be updated
        HSSFWorkbook wb;
        HSSFSheet worksheet;
        if(fIPS.available()>=512) {
            wb = new HSSFWorkbook(fIPS); //If there is already data in a workbook
            worksheet = wb.getSheetAt(0);
        }else{
            wb = new HSSFWorkbook();    //if the workbook was just created
            worksheet = wb.createSheet("Data");
        }
         //Access the worksheet, so that we can update / modify it
        HSSFRow row1 = worksheet.createRow(0);  //0 = row number
        int i=0;
        Cell c = row1.getCell(i);
        while (!(c == null || c.getCellType() == Cell.CELL_TYPE_BLANK)) {   //cell is empty
            i++;
            c=row1.getCell(i);
        }
        HSSFRow rowx;
        int x=0;
        for(String s : results) {
            rowx = worksheet.createRow(x);
            HSSFCell cellx = rowx.createCell(i);   //0 = column number
            cellx.setCellValue(s);
            x++;
        }
        fIPS.close(); //Close the InputStream
        FileOutputStream output_file =new FileOutputStream("test.xls");//Open FileOutputStream to write updates
        wb.write(output_file); //write changes
        output_file.close();  //close the stream

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Answer 1

我認為你是一次又一次地創建新的行和單元格並導致重寫excel。

基本上，您需要獲取行和單元格，而不是在程序中創建它們。

HSSFRow row1 = worksheet.createRow(0);

您可能需要獲取行而不是創建它。

HSSFRow row1 = worksheet.getRow(0);

https://poi.apache.org/apidocs/org/apache/poi/ss/usermodel/Sheet.html#getRow(int）

這個小例子更新了第二行的第二個單元格：

//Read the spreadsheet that needs to be updated
FileInputStream fsIP= new FileInputStream(new File("C:\\Excel.xls"));  
//Access the workbook                  
HSSFWorkbook wb = new HSSFWorkbook(fsIP);
//Access the worksheet, so that we can update / modify it. 
HSSFSheet worksheet = wb.getSheetAt(0); 
// declare a Cell object
Cell cell = null; 
// Access the second cell in second row to update the value
cell = worksheet.getRow(1).getCell(1);   
// Get current cell value value and overwrite the value
cell.setCellValue("OverRide existing value");
//Close the InputStream  
fsIP.close(); 
//Open FileOutputStream to write updates
FileOutputStream output_file =new FileOutputStream(new File("C:\\Excel.xls"));  
 //write changes
wb.write(output_file);
//close the stream
output_file.close();