Java POI实现Excel导入导出通用方法与样式处理

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.FileInputStream;
import java.io.IOException;

public class POIExample {
    public static void main(String[] args) throws IOException {
        FileInputStream excelFile = new FileInputStream("path/to/your/excel/file.xlsx");
        Workbook workbook = new XSSFWorkbook(excelFile);
        Sheet sheet = workbook.getSheetAt(0);

        for (Row row : sheet) {
            for (Cell cell : row) {
                // 示例：读取第一个单元格的值
                if (cell.getCellType() == CellType.STRING) {
                    System.out.print(cell.getStringCellValue());
                }
            }
        }
        workbook.close();
        excelFile.close();
    }
}

// 示例代码，创建HSSF和XSSF的工作簿
HSSFWorkbook hssfWorkbook = new HSSFWorkbook();
XSSFWorkbook xssfWorkbook = new XSSFWorkbook();

// 示例代码，读取XLSX文件
try (InputStream inp = new FileInputStream("example.xlsx")) {
    Workbook wb = new XSSFWorkbook(inp);
    Sheet sheet = wb.getSheetAt(0);
    // 处理Sheet中的数据
}

// 示例代码，写入数据到单元格
Cell cell = row.createCell(0);
cell.setCellValue("Hello, POI!");

SXSSFWorkbook workbook = new SXSSFWorkbook();
SXSSFSheet sheet = workbook.createSheet();
// 写入大量数据
for (int i = 0; i < 10000; i++) {
    SXSSFRow row = sheet.createRow(i);
    for (int j = 0; j < 10; j++) {
        SXSSFCell cell = row.createCell(j);
        cell.setCellValue("Test Data " + i + j);
    }
}
workbook.dispose(); // 清理临时文件

<!-- Apache POI core dependency -->
<dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi</artifactId>
  <version>5.2.3</version>
</dependency>
<!-- For Excel 2007+ (XSSF) support -->
<dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi-ooxml</artifactId>
  <version>5.2.3</version>
</dependency>

src/
|-- main/
    |-- java/
        |-- com/
            |-- mycompany/
                |-- myapp/
                    |-- model/
                        |-- ExcelData.java
                    |-- dao/
                        |-- ExcelDao.java
                    |-- service/
                        |-- ExcelService.java
                    |-- ExcelApplication.java
    |-- resources/
        |-- application.properties

# Excel文件上传路径
excel.upload.path=/path/to/upload/directory

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

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

public class ExcelReader {

    public static void main(String[] args) throws Exception {
        FileInputStream excelFile = new FileInputStream(new File("/path/to/your/excel/file.xlsx"));
        Workbook workbook = new XSSFWorkbook(excelFile);
        Sheet datatypeSheet = workbook.getSheetAt(0);
        Iterator<Row> iterator = datatypeSheet.iterator();
        iterator.next(); // 跳过标题行

        while (iterator.hasNext()) {
            Row currentRow = iterator.next();
            Iterator<Cell> cellIterator = currentRow.cellIterator();

            while (cellIterator.hasNext()) {
                Cell currentCell = cellIterator.next();
                // 根据单元格类型处理不同格式的数据
                switch (currentCell.getCellType()) {
                    case STRING:
                        System.out.print(currentCell.getStringCellValue() + "\t");
                        break;
                    case NUMERIC:
                        System.out.print(currentCell.getNumericCellValue() + "\t");
                        break;
                    case BOOLEAN:
                        System.out.print(currentCell.getBooleanCellValue() + "\t");
                        break;
                    case FORMULA:
                        System.out.print(currentCell.getCellFormula() + "\t");
                        break;
                    default:
                        System.out.print(" " + "\t");
                }
            }
            System.out.println();
        }
        workbook.close();
        excelFile.close();
    }
}

if (currentCell.getCellType() == CellType.NUMERIC) {
    if (DateUtil.isCellDateFormatted(currentCell)) {
        System.out.print(currentCell.getDateCellValue() + "\t");
    } else {
        System.out.print(currentCell.getNumericCellValue() + "\t");
    }
}

if (currentCell.getCellType() == CellType.BLANK) {
    System.out.print(" " + "\t");
}

if (currentCell.getCellType() == CellType.ERROR) {
    System.out.print("Error: " + currentCell.getErrorCellValue() + "\t");
}

import org.apache.poi.ss.usermodel.*;
import java.text.SimpleDateFormat;
import java.util.Date;

public void writeDataToExcel(Workbook workbook, List<User> users) {
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
    Sheet sheet = workbook.createSheet("Users");

    int rowNum = 0;
    for (User user : users) {
        Row row = sheet.createRow(rowNum++);
        int colNum = 0;
        row.createCell(colNum++).setCellValue(user.getId());
        row.createCell(colNum++).setCellValue(user.getName());
        row.createCell(colNum++).setCellValue(user.getEmail());
        row.createCell(colNum++).setCellValue(user.getAge());
        row.createCell(colNum).setCellValue(dateFormat.format(user.getBirthDate()));
    }
}

// 创建一个Excel文档
Workbook workbook = new XSSFWorkbook(); // 如果需要导出为.xlsx格式
// Workbook workbook = new HSSFWorkbook(); // 如果需要导出为.xls格式

// 创建一个工作表sheet
Sheet sheet = workbook.createSheet("DataExport");

// 假设有一个方法用于填充数据到工作表
writeDataToExcel(workbook, users);

// 将工作簿写入到文件输出流中
try (FileOutputStream outputStream = new FileOutputStream("Users.xlsx")) {
    workbook.write(outputStream);
} catch (IOException e) {
    e.printStackTrace();
} finally {
    try {
        workbook.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

// 创建工作簿和工作表
Workbook workbook = new HSSFWorkbook();
Sheet sheet = workbook.createSheet("Style Example");

// 创建单元格样式
CellStyle style = workbook.createCellStyle();
Font font = workbook.createFont();
font.setFontName("Arial");
font.setFontHeightInPoints((short) 12);
font.setColor(IndexedColors.RED.getIndex());

// 设置边框样式
style.setBorderBottom(BorderStyle.THIN);
style borderBottom Color(IndexedColors.BLACK.getIndex());

// 设置单元格数据类型
style.setDataFormat(workbook.createDataFormat().getFormat("@"));

// 设置对齐方式
style.setAlignment(HorizontalAlignment.CENTER);
style.setVerticalAlignment(VerticalAlignment.CENTER);

// 将样式应用到单元格
Cell cell = sheet.createRow(0).createCell(0);
cell.setCellValue(" Styled Text ");
cell.setCellStyle(style);

public class CellStyleCache {
    private Map<String, CellStyle> styleCache = new HashMap<>();

    public CellStyle getCellStyle(Workbook workbook, String key) {
        CellStyle style = styleCache.get(key);
        if (style == null) {
            style = createCellStyle(workbook, key);
            styleCache.put(key, style);
        }
        return style;
    }

    private CellStyle createCellStyle(Workbook workbook, String key) {
        // 逻辑创建一个样式，该方法类似于前面的样式创建示例
        // ...
    }
}

// 创建SXSSFWorkbook实例
SXSSFWorkbook workbook = new SXSSFWorkbook();

// 创建写入流
FileOutputStream fileOut = new FileOutputStream("large_file.xlsx");
SXSSFSheet sheet = workbook.createSheet("Large Data");

// 使用SXSSFWorkbook和SXSSFSheet添加数据
for (int i = 0; i < 100000; i++) {
    SXSSFRow row = sheet.createRow(i);
    SXSSFCell cell = row.createCell(0);
    cell.setCellValue("Data " + i);
}

// 写入文件并清理临时文件
workbook.write(fileOut);
workbook.dispose();
fileOut.close();