Maven依赖

• Excel2003或更早的版本

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>VERSION</version>
</dependency>

• Excel2007或更新的版本

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

Apache POI里面的基本概念

HSSF开头的API在2003或跟老的版本使用
XSSF开头的API在2007或更新的版本使用

• workbook excel文件，分为 HSSFWorkbook 和XSSFWorkbook
• sheet 页，分为HSSFSheet和XSSFSheet
• row 行，分为HSSFRow和XSSFRow
• cell 单元格，分为HSSFCell和XSSFCell

下面给出一个基础的代码

读Excel，一行一行，一格一格读取,假设你有一个这样的文件,有3列，书名，作者，价格

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

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

/**
 * A dirty simple program that reads an Excel file.
 * @author www.codejava.net
 *
 */
public class SimpleExcelReaderExample {
    
    public static void main(String[] args) throws IOException {
        String excelFilePath = "Books.xlsx";
        FileInputStream inputStream = new FileInputStream(new File(excelFilePath));
        
        Workbook workbook = new XSSFWorkbook(inputStream);
        Sheet firstSheet = workbook.getSheetAt(0);
        Iterator<Row> iterator = firstSheet.iterator();
        
        while (iterator.hasNext()) {
            Row nextRow = iterator.next();
            Iterator<Cell> cellIterator = nextRow.cellIterator();
            
            while (cellIterator.hasNext()) {
                Cell cell = cellIterator.next();
                
                switch (cell.getCellType()) {
                    case Cell.CELL_TYPE_STRING:
                        System.out.print(cell.getStringCellValue());
                        break;
                    case Cell.CELL_TYPE_BOOLEAN:
                        System.out.print(cell.getBooleanCellValue());
                        break;
                    case Cell.CELL_TYPE_NUMERIC:
                        System.out.print(cell.getNumericCellValue());
                        break;
                }
                System.out.print(" - ");
            }
            System.out.println();
        }
        
        workbook.close();
        inputStream.close();
    }

}

输出结果

Head First Java - Kathy Serria - 79.0 -
Effective Java - Joshua Bloch - 36.0 -
Clean Code - Robert Martin - 42.0 -
Thinking in Java - Bruce Eckel - 35.0 -

优化代码，使用面向对象特性

创建一个Book对象

public class Book {
    private String title;
    private String author;
    private float price;

    public Book() {
    }

    public String toString() {
        return String.format("%s - %s - %f", title, author, price);
    }

    // getters and setters
}

重构出一个单独的方法获取单元格的值

private Object getCellValue(Cell cell) {
    switch (cell.getCellType()) {
    case Cell.CELL_TYPE_STRING:
        return cell.getStringCellValue();

    case Cell.CELL_TYPE_BOOLEAN:
        return cell.getBooleanCellValue();

    case Cell.CELL_TYPE_NUMERIC:
        return cell.getNumericCellValue();
    }

    return null;
}

读取excel，返回一个List<Book>

public List<Book> readBooksFromExcelFile(String excelFilePath) throws IOException {
    List<Book> listBooks = new ArrayList<>();
    FileInputStream inputStream = new FileInputStream(new File(excelFilePath));

    Workbook workbook = new XSSFWorkbook(inputStream);
    Sheet firstSheet = workbook.getSheetAt(0);
    Iterator<Row> iterator = firstSheet.iterator();

    while (iterator.hasNext()) {
        Row nextRow = iterator.next();
        Iterator<Cell> cellIterator = nextRow.cellIterator();
        Book aBook = new Book();

        while (cellIterator.hasNext()) {
            Cell nextCell = cellIterator.next();
            int columnIndex = nextCell.getColumnIndex();

            switch (columnIndex) {
            case 1:
                aBook.setTitle((String) getCellValue(nextCell));
                break;
            case 2:
                aBook.setAuthor((String) getCellValue(nextCell));
                break;
            case 3:
                aBook.setPrice((double) getCellValue(nextCell));
                break;
            }


        }
        listBooks.add(aBook);
    }

    workbook.close();
    inputStream.close();

    return listBooks;
}

测试代码

public static void main(String[] args) throws IOException {
    String excelFilePath = "Books.xlsx";
    ExcelReaderExample2 reader = new ExcelReaderExample2();
    List<Book> listBooks = reader.readBooksFromExcelFile(excelFilePath);
    System.out.println(listBooks);
}

输出结果

[Head First Java - Kathy Serria - 79.000000, Effective Java - Joshua Bloch - 36.000000,
    Clean Code - Robert Martin - 42.000000, Thinking in Java - Bruce Eckel - 35.000000]

其他API方法

获取一个指定的sheet

Sheet thirdSheet = workbook.getSheetAt(2);

获取sheet的名字

String sheetName = sheet.getSheetName();

获取sheet的个数

int numberOfSheets = workbook.getNumberOfSheets();