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📜  Apache POI –电子表格

📅  最后修改于: 2020-11-18 09:01:33             🧑  作者: Mango

本章说明如何创建电子表格并使用Java对其进行操作。电子表格是Excel文件中的页面；它包含具有特定名称的行和列。

完成本章后，您将能够创建电子表格并对其执行读取操作。

创建一个电子表格

首先，让我们使用前面各章中讨论的引用类创建电子表格。通过遵循上一章，首先创建一个工作簿，然后我们可以继续创建工作表。

以下代码段用于创建电子表格。

//Create Blank workbook
XSSFWorkbook workbook = new XSSFWorkbook();

//Create a blank spreadsheet
XSSFSheet spreadsheet = workbook.createSheet("Sheet Name");

电子表格上的行

电子表格具有网格布局。行和列用特定名称标识。列用字母标识，行用数字标识。

以下代码段用于创建一行。

XSSFRow row = spreadsheet.createRow((short)1);

写入电子表格

让我们考虑一个雇员数据的例子。在此，员工数据以表格形式给出。

Emp Id Emp Name Designation
Tp01 Gopal Technical Manager
TP02 Manisha Proof Reader
Tp03 Masthan Technical Writer
Tp04 Satish Technical Writer
Tp05 Krishna Technical Writer

以下代码用于将以上数据写入电子表格。

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.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class Writesheet {
   public static void main(String[] args) throws Exception {

      //Create blank workbook
      XSSFWorkbook workbook = new XSSFWorkbook(); 

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

      //Create row object
      XSSFRow row;

      //This data needs to be written (Object[])
      Map < String, Object[] > empinfo = 
      new TreeMap < String, Object[] >();
      empinfo.put( "1", new Object[] { "EMP ID", "EMP NAME", "DESIGNATION" });
      empinfo.put( "2", new Object[] { "tp01", "Gopal", "Technical Manager" });
      empinfo.put( "3", new Object[] { "tp02", "Manisha", "Proof Reader" });
      empinfo.put( "4", new Object[] { "tp03", "Masthan", "Technical Writer" });
      empinfo.put( "5", new Object[] { "tp04", "Satish", "Technical Writer" });
      empinfo.put( "6", new Object[] { "tp05", "Krishna", "Technical Writer" });
      
      //Iterate over data and write to sheet
      Set < String > keyid = empinfo.keySet();
      int rowid = 0;

      for (String key : keyid) {
         row = spreadsheet.createRow(rowid++);
         Object [] objectArr = empinfo.get(key);
         int cellid = 0;

         for (Object obj : objectArr) {
            Cell cell = row.createCell(cellid++);
            cell.setCellValue((String)obj);
         }
      }

      //Write the workbook in file system
      FileOutputStream out = new FileOutputStream(new File("Writesheet.xlsx"));
      workbook.write(out);
      out.close();
      System.out.println("Writesheet.xlsx written successfully");
   }
}

将上面的Java代码另存为Writesheet.java ，然后从命令提示符下编译并运行它，如下所示：

$javac Writesheet.java
$java Writesheet

它将编译并执行，以在当前目录中生成一个名为Writesheet.xlsx的Excel文件，您将在命令提示符下获得以下输出。

Writesheet.xlsx written successfully

Writesheet.xlsx文件如下所示。

书写纸

从电子表格中读取

让我们将上述名为Writesheet.xslx的excel文件作为输入。遵守以下代码；它用于从电子表格中读取数据。

import java.io.File;
import java.io.FileInputStream;

import java.util.Iterator;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class Readsheet {
   static XSSFRow row;
   public static void main(String[] args) throws Exception {
      FileInputStream fis = new FileInputStream(new File("WriteSheet.xlsx"));
      
      XSSFWorkbook workbook = new XSSFWorkbook(fis);
      XSSFSheet spreadsheet = workbook.getSheetAt(0);
      Iterator < Row >  rowIterator = spreadsheet.iterator();
      
      while (rowIterator.hasNext()) {
         row = (XSSFRow) rowIterator.next();
         Iterator < Cell >  cellIterator = row.cellIterator();
         
         while ( cellIterator.hasNext()) {
            Cell cell = cellIterator.next();
            
            switch (cell.getCellType()) {
               case Cell.CELL_TYPE_NUMERIC:
                  System.out.print(cell.getNumericCellValue() + " \t\t ");
                  break;
               
               case Cell.CELL_TYPE_STRING:
                  System.out.print(
                  cell.getStringCellValue() + " \t\t ");
                  break;
            }
         }
         System.out.println();
      }
      fis.close();
   }
}

让我们将上面的代码保存在Readsheet.java文件中，然后从命令提示符下编译并运行它，如下所示：

$javac Readsheet.java
$java Readsheet

如果您的系统环境配置了POI库，它将在命令提示符下编译并执行以生成以下输出。

EMP ID   EMP NAME       DESIGNATION 
 tp01     Gopal       Technical Manager 
 tp02     Manisha     Proof Reader 
 tp03     Masthan     Technical Writer 
 tp04     Satish      Technical Writer 
 tp05     Krishna     Technical Writer