NoClassDefFoundError: UnsupportedFileFormatException while working with excel sheet using java

Question

我正在编写一个 Java 程序，该程序从 .xlsx 文件读取并以 .csv 格式提供输出。这是我的代码：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.text.SimpleDateFormat; 
import java.util.Date;
import java.util.Iterator;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.poi.ss.usermodel.Cell;   
import org.apache.poi.ss.usermodel.DateUtil;
import org.apache.poi.ss.usermodel.Row;

public class xlsxToCsv {

    public static void main(String[] args) {

        long startTime = System.currentTimeMillis();

        File inputFile = new File("C:\inputFile.xlsx");
        File outputFile = new File("C:\outputFile.csv");

        xlsx(inputFile, outputFile);

        long stopTime = System.currentTimeMillis();
        long elapsedTime = stopTime - startTime;

        System.out.println(elapsedTime);

   }

   private static void xlsx(File inputFile, File outputFile) {

        //for storing data into CSV files
        StringBuffer data = new StringBuffer();

        try {

            Writer w = new OutputStreamWriter(new FileOutputStream(outputFile), "UTF-8");

            // Get the workbook object for XLS file
            XSSFWorkbook workbook = new XSSFWorkbook(new FileInputStream(inputFile));

            // Get first sheet from the workbook
            XSSFSheet sheet = workbook.getSheetAt(0);
            Cell cell;
            Row row;

            // Iterate through each rows from first sheet
            Iterator<Row> rowIterator = sheet.iterator();
            while (rowIterator.hasNext()) 
            {
                row = rowIterator.next();
                // For each row, iterate through each columns
                Iterator<Cell> cellIterator = row.cellIterator();
                while (cellIterator.hasNext()) 
                {
                    cell = cellIterator.next();

                    switch (cell.getCellType()) 
                    {
                        case Cell.CELL_TYPE_BOOLEAN:
                            data.append(cell.getBooleanCellValue() + ",");
                            break;

                        case Cell.CELL_TYPE_NUMERIC:
                            if(DateUtil.isCellDateFormatted(cell)) {
                                Date date = cell.getDateCellValue();
                                System.out.println(date.toString());
                                SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
                                String d = sdf.format(date);
                                System.out.println(d);
                                data.append(d + ",");   
                            }
                            else if(cell.getNumericCellValue() == (int)cell.getNumericCellValue())
                                data.append((int)cell.getNumericCellValue() + ",");
                            else if(cell.getNumericCellValue() == (long)cell.getNumericCellValue())
                                data.append((long)cell.getNumericCellValue() + ",");
                            else
                                data.append(cell.getNumericCellValue() + ",");
                            break;

                        case Cell.CELL_TYPE_STRING:
                                data.append((cell.getStringCellValue()) + ",");
                                break;

                        case Cell.CELL_TYPE_BLANK:
                                data.append("" + ",");
                                break;

                        default:
                                data.append(cell + ",");
                        }

                        //data.append('\n'); 
                }
                data.append("\r\n");
        }

        w.write(data.toString());
        w.close();

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

}

但是，我收到以下错误：

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/poi/UnsupportedFileFormatException
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access0(Unknown Source)
at java.net.URLClassLoader.run(Unknown Source)
at java.net.URLClassLoader.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at xlsxToCsv.xlsxToCsv.xlsx(xlsxToCsv.java:47)
at xlsxToCsv.xlsxToCsv.main(xlsxToCsv.java:28)
Caused by: java.lang.ClassNotFoundException: org.apache.poi.UnsupportedFileFormatException
at java.net.URLClassLoader.run(Unknown Source)
at java.net.URLClassLoader.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 14 more

我包含了以下 jar：

dom4j-1.6.jar
poi-3.9.jar
poi-ooxml-3.11.jar
poi-ooxml-schemas-3.8-20120326.jar
xmlbeans-2.3.0.jar

我已经检查了文件格式是 .xlsx 和目录，但我不明白问题是什么。

如何消除这个错误？

Answer 1

NoClassDefFoundError 当 JVM 在运行时无法找到库时出现。可能是您在文件路径中添加了库，但它在运行时间不可用。

Answer 2

这在 Apache POI FAQ page:

Can I mix POI jars from different versions?

No. This is not supported.

All POI jars in use must come from the same version. A combination such as poi-3.11.jar and poi-ooxml-3.9.jar is not supported, and will fail to work in unpredictable ways.

您将自己列为使用来自不同版本的 poi-3.9.jar 和 poi-ooxml-3.11.jar，将无法正常工作。

您需要确保所有 POI jar 都来自同一版本。我建议您获取 latest POI release from the download page（撰写本文时为 3.12），并使用

中的一组一致的罐子

Answer 3

我也试过同样的错误。这是因为 poi 罐子在 pom.xml 文件中重复。

我收到了这些警告，但我先忽略了这些警告。后来我尝试删除 pom.xml 中重复的 poi 罐子，这解决了问题。

这是我之前收到的警告：

[WARNING] Some problems were encountered while building the effective model for MavenProj:Perfumania:jar:0.0.1-SNAPSHOT [WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: org.apache.poi:poi:jar -> duplicate declaration of version 3.9 @ line 36,

Answer 4

原因是 poi 的版本，poi-ooxml，poi-ooxml-schemas 应该相同，例如您 rpom.xml 文件中的版本应该是 3.6

NoClassDefFoundError: UnsupportedFileFormatException while working with excel sheet using java

NoClassDefFoundError: UnsupportedFileFormatException while working with excel sheet using java

java

excel

xlsx

apache-poi

xssf