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[英]Appending sheet to existing excel file using Java and Apache POI
[英]Appending a sheet to an Excel file using Apache POI - POIXMLException caused by NullPointerException
这是我的代码:
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.xssf.usermodel.*;
public class testingsyncclass {
public static void main(String[] args) throws IOException, InvalidFormatException{
writeParametersTableToFile("C:/ENTERPRISE_TESTING", "XLSX_TEST", "SHEETNAME");
}
public static void writeParametersTableToFile(String fileLocation, String fileName, String tableLocator) throws InvalidFormatException{
String[] columnHeaders = {"What", "is", "a", "computer", "?"};
ArrayList<Object[]> xlsxFileData = new ArrayList<Object[]>();
for(int i = 0; i < 10; i++){
Object[] o = {"CoffeeCup", "AnglerJS", "Emerald", "C♭", "C--"};
xlsxFileData.add(o);
}
try{
if(fileName.contains(".xlsx")){
fileName = fileName.replaceAll(".xlsx", "");
}
File file = new File(fileLocation);
if(file.mkdirs() || file.exists()){
File excelFile = new File(fileLocation + "/" + fileName + ".xlsx");
XSSFWorkbook workbook;
XSSFSheet sheet;
if(excelFile.exists()){
workbook = new XSSFWorkbook(excelFile);
} else {
workbook = new XSSFWorkbook();
}
if(workbook.getSheet(tableLocator)==null){
sheet = workbook.createSheet(tableLocator);
} else {
sheet = workbook.createSheet("NEW_TEST_SHEET");
}
XSSFRow firstRow = sheet.createRow(0);
//write headers
for(int i = 0; i < columnHeaders.length; i++){
XSSFCell cell = firstRow.createCell(i);
cell.setCellValue(columnHeaders[i]);
}
//write data
for(int i = 0; i < xlsxFileData.size(); i++){
XSSFRow row = sheet.createRow(i+1);
for(int j = 0; j < xlsxFileData.get(i).length; j++){
XSSFCell cell = row.createCell(j);
String value = (String) xlsxFileData.get(i)[j];
cell.setCellValue(value);
}
}
FileOutputStream fileOut = new FileOutputStream(fileLocation + "/" + fileName + ".xlsx");
//write this workbook to an Outputstream.
System.out.println(fileOut + " (fileout)");
System.out.println(workbook + " (workbook)");
workbook.write(fileOut);
fileOut.flush();
fileOut.close();
workbook.close();
} else {
System.err.println(fileLocation + " was an invalid directory.");
}
} catch (IOException e){
System.err.println("Something went wrong!");
e.printStackTrace();
}
}
}
创建文件可以正常工作-文件已按预期创建。 但是,如果文件存在,我希望此方法创建一个工作表并将其添加到工作簿中。 使用我目前拥有的代码,我得到以下异常:
Exception in thread "main" org.apache.poi.POIXMLException: java.lang.NullPointerException
at org.apache.poi.POIXMLDocument.getProperties(POIXMLDocument.java:168)
at org.apache.poi.POIXMLDocument.write(POIXMLDocument.java:246)
at testframework.testingsyncclass.writeParametersTableToFile(testingsyncclass.java:67)
at testframework.testingsyncclass.main(testingsyncclass.java:17)
Caused by: java.lang.NullPointerException
workbook.write(fileOut)
此异常的行是workbook.write(fileOut)
但workbook和fileOut都不为空。 在第二次运行时,输出文件也会损坏。
我究竟做错了什么?
造成此错误的原因是,在创建工作簿时,我没有将FileInputStream作为参数传递。 尽管该API建议您可以将文件/路径作为参数传递,但实际上该文件以ReadOnly模式打开-因此,当再次对其进行写入时,将引发异常。
通过传入FileInputStream来解决此问题。 然后我的代码变为:
FileInputStream fis = new FileInputStream(excelFile);
workbook = new XSSFWorkbook(fis);
工作簿wb = WorkbookFactory.create(new FileInputStream(“ data / df.xlsx”));;
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