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。每次运行代码时，都会收到如下所示的错误。我也尝试过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)

请查看下面的代码。谢谢你的帮助。

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

如果你把

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

//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");

会成功的!

Answer 2

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

我也不得不使用XSSFRow而不是HSSFRow，但除此之外，它对我来说工作得很好。

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

我尝试了这个，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");
    }
}