Apache POI XSSFWorkbook 為文件拋出 NullPointerException

Question

我在這里檢查了所有可能的問題，有一個類似的問題，但沒有一個解決方案有效。 我覺得我錯過了一些非常明顯的東西，但我就是看不到它。

I am on Windows 10, using Eclipse 2019, and the newest Apache POI jar files (not maven) with xmlbeans version 3.1.0. 我想讀取一個 xlsx 文件，但是每次我運行我的代碼（這是我在多個網站和視頻上看到並成功運行的一個基本示例）時，我都會在創建工作簿的行收到“NullPointerException” ：

import java.io.File;
//import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
//import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class excelImportTest {


    public static void main (String args[]) throws IOException, InvalidFormatException {

      // Linking file to Workbook
      // ****Where exception is called every time****
      XSSFWorkbook wb = new XSSFWorkbook(new File("C:\\Users\\Owner\\Downloads\\TestData.xlsx"));

      // Pulling sheet from Workbook
      XSSFSheet sheet = wb.getSheetAt(0);

      // Get iterator to all the rows in current sheet
      Iterator<Row> rowIterator = sheet.iterator();

      // Traversing over each row of XLSX file
      while (rowIterator.hasNext()) {
          Row row = rowIterator.next();

          // For each row, iterate through each columns
          Iterator<Cell> cellIterator = row.cellIterator();

          while (cellIterator.hasNext()) {
              Cell cell = cellIterator.next();
              switch(cell.getCellType()) {
              case STRING:
                  System.out.print(cell.getStringCellValue() + "\t");
                  break;
              case NUMERIC:
                  System.out.print(cell.getNumericCellValue() + "\t");
                  break;
              case BOOLEAN:
                  System.out.print(cell.getBooleanCellValue() + "\t");
                  break;
              default :
              }
          }
      }
      wb.close();

這是我收到的異常：

Exception in thread "main" java.lang.ExceptionInInitializerError
    at sun.misc.Unsafe.ensureClassInitialized(Native Method)
    at sun.reflect.UnsafeFieldAccessorFactory.newFieldAccessor(Unknown Source)
    at sun.reflect.ReflectionFactory.newFieldAccessor(Unknown Source)
    at java.lang.reflect.Field.acquireFieldAccessor(Unknown Source)
    at java.lang.reflect.Field.getFieldAccessor(Unknown Source)
    at java.lang.reflect.Field.get(Unknown Source)
    at org.apache.xmlbeans.XmlBeans.typeSystemForClassLoader(XmlBeans.java:775)
    at org.openxmlformats.schemas.drawingml.x2006.main.ThemeDocument.<clinit>(Unknown Source)
    at org.openxmlformats.schemas.drawingml.x2006.main.ThemeDocument$Factory.parse(Unknown Source)
    at org.apache.poi.xssf.model.ThemesTable.<init>(ThemesTable.java:86)
    at org.apache.poi.ooxml.POIXMLFactory.createDocumentPart(POIXMLFactory.java:61)
    at org.apache.poi.ooxml.POIXMLDocumentPart.read(POIXMLDocumentPart.java:684)
    at org.apache.poi.ooxml.POIXMLDocument.load(POIXMLDocument.java:180)
    at org.apache.poi.xssf.usermodel.XSSFWorkbook.<init>(XSSFWorkbook.java:288)
    at org.apache.poi.xssf.usermodel.XSSFWorkbook.<init>(XSSFWorkbook.java:325)
    at excelImportTest.main(excelImportTest.java:62)
Caused by: java.lang.RuntimeException: Could not instantiate SchemaTypeSystemImpl (java.lang.reflect.InvocationTargetException): is the version of xbean.jar correct?
    at schemaorg_apache_xmlbeans.system.sD023D6490046BA0250A839A9AD24C443.TypeSystemHolder.loadTypeSystem(Unknown Source)
    at schemaorg_apache_xmlbeans.system.sD023D6490046BA0250A839A9AD24C443.TypeSystemHolder.<clinit>(Unknown Source)
    ... 16 more
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    ... 18 more
Caused by: java.lang.NullPointerException
    at org.apache.xmlbeans.impl.schema.ClassLoaderResourceLoader.getResourceAsStream(ClassLoaderResourceLoader.java:33)
    at org.apache.xmlbeans.impl.schema.SchemaTypeSystemImpl$XsbReader.getLoaderStream(SchemaTypeSystemImpl.java:2249)
    at org.apache.xmlbeans.impl.schema.SchemaTypeSystemImpl$XsbReader.<init>(SchemaTypeSystemImpl.java:1522)
    at org.apache.xmlbeans.impl.schema.SchemaTypeSystemImpl.initFromHeader(SchemaTypeSystemImpl.java:273)
    at org.apache.xmlbeans.impl.schema.SchemaTypeSystemImpl.<init>(SchemaTypeSystemImpl.java:185)
    ... 22 more

我已經嘗試了我能想到的所有選項組合以及我在網上找到的建議：

• 我創建了一個單獨的 FileInputStream(new File(...))，並運行了一個 if 語句來查看它是否是 null。 這返回了“not null”，但是當它到達上面的行時我仍然得到了異常
• 我嘗試使用嵌套的 new FileInputStream(new File(...)) 格式運行該行，並收到相同的錯誤
• 我一直在使用 try-catch 塊來處理異常，但在中止程序之前它似乎沒有標記異常
• 我嘗試使用包含 Apache-POI 的 OCPPackage.open(new File(...)) 方法，並得到相同的錯誤

我是否缺少任何明顯的方法，或者這是否源於我的設置中的其他問題？

編輯

由於看來我的問題可能出在我引用的 .jar 文件中，因此這是文件構建路徑的一部分：

Answer 1

我認為您沒有正確添加 jars。

First go to this url: https://archive.apache.org/dist/poi/release/bin/ and download poi-bin-4.1.2-20200217.zip from there.

現在提取 zip 並將此 jars 添加到標有紅色的項目中。

我已經測試了您的代碼及其工作。

import java.io.File;
import java.io.IOException;
import java.util.Iterator;

import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class Testing {
    public static void main(String args[]) throws IOException, InvalidFormatException {

        // Linking file to Workbook
        // ****Where exception is called every time****
        XSSFWorkbook wb = new XSSFWorkbook(new File("C:\\Users\\Anish\\Downloads\\TestData.xlsx"));

        System.out.println("Workbook loaded");

        // Pulling sheet from Workbook
        XSSFSheet sheet = wb.getSheetAt(0);

        // Get iterator to all the rows in current sheet
        Iterator<Row> rowIterator = sheet.iterator();

        // Traversing over each row of XLSX file
        while (rowIterator.hasNext()) {
            Row row = rowIterator.next();

            // For each row, iterate through each columns
            Iterator<Cell> cellIterator = row.cellIterator();

            while (cellIterator.hasNext()) {
                Cell cell = cellIterator.next();
                switch (cell.getCellType()) {
                case STRING:
                    System.out.print(cell.getStringCellValue() + "\t");
                    break;
                case NUMERIC:
                    System.out.print(cell.getNumericCellValue() + "\t");
                    break;
                case BOOLEAN:
                    System.out.print(cell.getBooleanCellValue() + "\t");
                    break;
                default:
                }
            }
        }
        wb.close();

    }
}

Output：

現在，如果您在項目中使用 maven。那么，您不需要在類路徑中添加 jars。

只需在pom.xml中添加此依賴項。

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>4.1.2</version>
</dependency>
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>4.1.2</version>
</dependency>

Answer 2

So after much troubleshoooting, I abandoned using the Apache POI jar files, and switched to using maven and adding apache poi as a dependancy, and my code now runs successfully.

也感謝所有提供幫助和建議的人，盡管我仍然不確定 Eclipse 和 POI jar 文件之間的通信問題的根源。