使用 Apache POI 更新 excel 文件

Question

我正在尝试使用 Apache POI 更新现有的 excel 文件。每次我运行我的代码时，我都会收到如下所示的错误。我也试过 FileInputStreamNewFile 的东西。

Exception in thread "main" java.lang.NullPointerException
    at com.gma.test.WriteExcelTest.writeXLSXFile(WriteExcelTest.java:26)
    at com.gma.test.WriteExcelTest.main(WriteExcelTest.java:44)

请在下面找到代码。感谢您的帮助。

package com.gma.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class WriteExcelTest {

    public static void writeXLSXFile(int row, int col) throws IOException {
        try {
            FileInputStream file = new FileInputStream("C:\\Anuj\\Data\\Data.xlsx");

            XSSFWorkbook workbook = new XSSFWorkbook(file);
            XSSFSheet sheet = workbook.getSheetAt(0);
            Cell cell = null;

            //Update the value of cell
            cell = sheet.getRow(row).getCell(col);
            cell.setCellValue("Pass");

            file.close();

            FileOutputStream outFile =new FileOutputStream(new File("C:\\Anuj\\Data\\Data.xlsx"));
            workbook.write(outFile);
            outFile.close();

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

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        writeXLSXFile(3, 3);
    }

}

Answer 1

如果你替换

//Update the value of cell
cell = sheet.getRow(row).getCell(col);
cell.setCellValue("Pass");

有

//Retrieve the row and check for null
HSSFRow sheetrow = sheet.getRow(row);
if(sheetrow == null){
    sheetrow = sheet.createRow(row);
}
//Update the value of cell
cell = sheetrow.getCell(col);
if(cell == null){
    cell = sheetrow.createCell(col);
}
cell.setCellValue("Pass");

它会起作用的！

Answer 2

感谢 Jelle Heuzel 提供了一个很好的例子。
我只是想添加生成的工作代码，以便其他人可以更快地将其合并到他们的代码中。

我还必须使用 XSSFRow 而不是 HSSFRow，但除此之外它对我来说效果很好。

package stackoverflow.appachePOI;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class WriteExcelTest {

    public static void writeXLSXFile(int row, int col) throws IOException {
        try {
            FileInputStream file = new FileInputStream("C:\\Users\\Sam\\files\\Masterproef lca\\lca-analysebeheer\\Test-Files\\exceltemplates\\template.xlsx");

            XSSFWorkbook workbook = new XSSFWorkbook(file);
            XSSFSheet sheet = workbook.getSheetAt(0);
            Cell cell = null;

            //Retrieve the row and check for null
            XSSFRow sheetrow = sheet.getRow(row);
            if(sheetrow == null){
                sheetrow = sheet.createRow(row);
            }
            //Update the value of cell
            cell = sheetrow.getCell(col);
            if(cell == null){
                cell = sheetrow.createCell(col);
            }
            cell.setCellValue("Pass");

            file.close();

            FileOutputStream outFile =new FileOutputStream(new File("C:\\Users\\Sam\\files\\Masterproef lca\\lca-analysebeheer\\Test-Files\\exceltemplates\\Output.xlsx"));
            workbook.write(outFile);
            outFile.close();

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

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        writeXLSXFile(3, 3);
    }

}

Answer 3

我试过这个并为 XLSX 和 XSSF 工作

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class TestStackOver {

    public static void writeXLSXFile(int row, int col) throws IOException {
        try {
            FileInputStream file = new FileInputStream(Constante.ruta);
            XSSFWorkbook workbook = new XSSFWorkbook(file);
            XSSFSheet sheet = workbook.getSheetAt(0);
            Cell cell = null;
          //Retrieve the row and check for null
            XSSFRow sheetrow = sheet.getRow(row);
            if(sheetrow == null){
                sheetrow = sheet.createRow(row);
            }
            //Update the value of cell
            cell = sheetrow.getCell(col);
            if(cell == null){
                cell = sheetrow.createCell(col);
            }
            cell.setCellValue("Pass");

            file.close();


            FileOutputStream outFile =new FileOutputStream(new File(Constante.ruta_salida));
            workbook.write(outFile);
            outFile.close();

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

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        System.out.println("inicio");
        writeXLSXFile(1, 14);
        System.out.println("terminado");
    }

}