在Java Apache POI中更新现有Excel文件

Question

我正在尝试编写一个Java程序，该程序将每天运行（使用任务调度器），并在每次运行时向Excel电子表格中添加一列。我遇到的问题是，它只是重新写入文件，而不是附加到文件中。我正在使用Apache POI，以下是相关代码：

 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

我认为您一次又一次地创建新的行和单元格，并导致重新编写excel。

实际上，您需要获取行和单元格，而不是在程序中创建它们。

HSSFRow row1 = worksheet.createRow(0);

您可能需要获取行，而不是创建行。

HSSFRow row1 = worksheet.getRow(0);

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

这个小示例更新第二行的第二个单元格：

//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();