使用excel工作簿时发生异常

Question

当我使用poi JAR在excel工作簿中写入一些数据时，代码中出现了以下异常：

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.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at WorkBookDemo.main(WorkBookDemo.java:27)
Caused by: java.lang.ClassNotFoundException: org.apache.poi.UnsupportedFileFormatException
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 13 more

我添加了以下罐子：

>

xmlbeans-2.4.0

poi-ooxml-schemas-3.11

poi-3.11

commons-logging-1.1

dom4j-1.6.1

log4j-1.2.17

import java.io.File;
import java.io.FileOutputStream;

import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

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 WorkBookDemo {

   public static void main(String[] args)
   {
        //Blank workbook
        XSSFWorkbook workbook = new XSSFWorkbook();

        //Create a blank sheet
        XSSFSheet sheet = workbook.createSheet("Employee Data");

        //This data needs to be written (Object[])
        Map<String, Object[]> data = new TreeMap<String, Object[]>();
        data.put("1", new Object[] {"ID", "NAME", "LASTNAME"});
        data.put("2", new Object[] {1, "Amit", "Shukla"});
        data.put("3", new Object[] {2, "Lokesh", "Gupta"});
        data.put("4", new Object[] {3, "John", "Adwards"});
        data.put("5", new Object[] {4, "Brian", "Schultz"});

       //Iterate over data and write to sheet
        Set<String> keyset = data.keySet();
        int rownum = 0;
        for (String key : keyset)
        {
            Row row = sheet.createRow(rownum++);
            Object [] objArr = data.get(key);
            int cellnum = 0;
            for (Object obj : objArr)
            {
                Cell cell = row.createCell(cellnum++);
                if(obj instanceof String)
                    cell.setCellValue((String)obj);
                else if(obj instanceof Integer)
                    cell.setCellValue((Integer)obj);
            }
        }
        try
        {
        //Write the workbook in file system
            FileOutputStream out = new FileOutputStream(new File("exps.xlsx"));
            workbook.write(out);
            out.close();
            System.out.println("exps.xlsx written successfully on disk.");
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

}

Answer 1

FileOutputStream out = new FileOutputStream(new File("exps.xlsx"));

文件输出流是用于将数据写入文件或文件描述符的输出流。文件是否可用或是否可以创建取决于底层平台。特别是某些平台，一次只允许一个FileOutputStream（或其他文件写入对象）打开一个文件进行写入。在这种情况下，如果所涉及的文件已经打开，则此类中的构造函数将失败。

因为您正在显式创建一个文件对象，并将其传递给文件输出流构造函数。它假定文件“exps.xlsx”已经创建。[参考。]

如果不是，您只需在FileOutputStream构造函数中传递文件的名称。

FileOutputStream out = new FileOutputStream("exps.xlsx");

如果文件尚未创建，则会自动创建该文件。

此外，我测试了您给定的代码，并使用了以下Maven依赖项，它成功了。

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>3.10-FINAL</version>
</dependency>
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>3.10</version>
</dependency>

如果您没有使用maven项目，您可以显式地添加上述版本的jar。