無法將數據寫入Excel文件單元格

Question

我想使用Java和apache庫poi將字符串寫入現有的Excel文件單元中。 這是我的方法：

public void setSuccessMessageInExcellFile(File uploadFile, HttpServletResponse response) {          

    try {
        FileInputStream fileInputStream = new FileInputStream(uploadFile);

        HSSFWorkbook workbook = new HSSFWorkbook(fileInputStream);
        HSSFSheet excelSheet = workbook.getSheetAt(0); 
        HSSFCell cell = excelSheet.getRow(0).getCell(0);
        cell.setCellValue("Imported");

        fileInputStream.close();
        FileOutputStream out = new FileOutputStream(uploadFile);
        workbook.write(out);
        out.close();
    } catch(Exception ex) {
        ex.getCause().printStackTrace();
    }           
}

沒有錯誤，但是“導入的”文本在我的Excel文件中不可用 。

Answer 1

確保您的文件存在，可寫並且具有正確的Excel版本。 之后，您應該像這樣更改代碼，因為否則會得到NullPointerException ：

public void setSuccessMessageInExcellFile(File uploadFile, HttpServletResponse response) {


    try {
        FileInputStream fileInputStream = new FileInputStream(uploadFile);

        HSSFWorkbook workbook = new HSSFWorkbook(fileInputStream);
        HSSFSheet excelSheet = workbook.getSheetAt(0); 
        HSSFCell cell = excelSheet.createRow(0).createCell(0);
        cell.setCellValue("Imported");

        fileInputStream.close();
        FileOutputStream out = new FileOutputStream(uploadFile);
        workbook.write(out);
        out.close();
    } catch(Exception ex) {
        ex.getCause().printStackTrace();
    } 
}

更好的方法是將可關閉對象放在try這樣的參數中：

try(FileInputStream fileInputStream = new FileInputStream(uploadFile);
            HSSFWorkbook workbook = new HSSFWorkbook(fileInputStream); 
            FileOutputStream out = new FileOutputStream(uploadFile)) {            
        HSSFSheet excelSheet = workbook.getSheetAt(0); 
        HSSFCell cell = excelSheet.createRow(0).createCell(0);
        cell.setCellValue("Imported"); 
        workbook.write(out);         
    } catch(Exception ex) {
        ex.getCause().printStackTrace();
    }