用poi-ooxml导出/读取Excel文件

使用依赖

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>4.1.2</version>
</dependency>

自定义注解

注解使用在实体类上，表示哪些字段的值需要到处到 excel 表格中

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ExcelHeader {
    /**
     * 表头
     * @return
     */
    String value() default "";
    /**
     * 列索引
     * @return
     */
    int columnIndex() default 0;
}

实体类

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {

    @ExcelHeader(value = "账号")
    private String username;

    @ExcelHeader(value = "密码")
    private String password;

    @ExcelHeader(value = "生日")
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private LocalDateTime birthday;

    // 该字段没有添加注解, Excel不导出
    private Integer age;

    public User(String username, String password, LocalDateTime birthday) {
        this.username = username;
        this.password = password;
        this.birthday = birthday;
    }
}

导出代码

@Slf4j
class IdcPoiApplicationTests {

    @Test
    void contextLoads() throws NoSuchFieldException, IllegalAccessException, IOException {
        // 创建模拟数据
        User user1 = new User("admin", "123456", LocalDateTime.now());
        User user2 = new User("test", "123456", LocalDateTime.now());
        List<User> users = Arrays.asList(user1, user2);

        // 文件路径
        String basePath =  "/Users/cuishiying/Documents/spring-cloud-learning/idc-poi/oss/";
        String fileName = new SimpleDateFormat("yyyyMMddHHmmss").format(new Date()).toString() +".xls";

        // 将Excel写入文件
        HSSFWorkbook workbook = exportExcel(users, User.class);
        workbook.setSheetName(0,"sheetName");//设置sheet的Name

        // 无论是通过HttpServletResponse导出还是导出到本地磁盘,本质都是IO操作，所以这里将IO操作提取到外层。
        workbook.write(new File(basePath + File.separator + fileName));
    }

    /**
     *
     * @param data 需要导出的数据
     * @param clz 数据对应的实体类
     * @param <T> 泛型
     * @return Excel文件
     * @throws NoSuchFieldException
     * @throws IllegalAccessException
     */
    public <T> HSSFWorkbook exportExcel(List<T> data, Class<T> clz) throws NoSuchFieldException, IllegalAccessException {

        Field[] fields = clz.getDeclaredFields();
        List<String> headers = new LinkedList<>();
        List<String> variables = new LinkedList<>();

        // 创建工作薄对象
        HSSFWorkbook workbook=new HSSFWorkbook();//这里也可以设置sheet的Name
        // 创建工作表对象
        HSSFSheet sheet = workbook.createSheet();
        // 创建表头
        Row rowHeader = sheet.createRow(0);

        // 表头处理
        //根据实体类的自定义注解来创建表头值
        for (int h = 0; h < fields.length; h++) {
            Field field = fields[h];
            if (field.isAnnotationPresent(ExcelHeader.class)) {
                // 表头
                ExcelHeader annotation = field.getAnnotation(ExcelHeader.class);
                headers.add(annotation.value());
                rowHeader.createCell(h).setCellValue(annotation.value());

                // 每个字段名
                variables.add(field.getName());
            }
        }

        // 数据处理
        for (int i = 0; i < data.size() ; i++) {

            //创建工作表的行(表头占用1行, 这里从第二行开始)
            HSSFRow row = sheet.createRow(i + 1);
            // 获取一行数据
            T t = data.get(i);
            Class<?> aClass = t.getClass();
            // 填充列数据
            for (int j = 0; j < variables.size(); j++) {

                Field declaredField = aClass.getDeclaredField(variables.get(j));
                declaredField.setAccessible(true);

                String key = declaredField.getName();
                Object value = declaredField.get(t);

                row.createCell(j).setCellValue(value.toString());
            }
        }
        log.info("Excel文件创建成功");
        return workbook;
    }

}

读取 excel

	File file = new File("C:\\user\\desktop\\文件.xlsx");
    XSSFWorkbook sheets= new XSSFWorkbook(new FileInputStream());
    //System.out.println(sheets.getNumberOfSheets());  获取总sheet表个数
    for(int i = 0; i < sheets.getNumberOfSheets(); i ++){
    	//获取单个sheet
    	XSSFSheet sheet = sheets.getSheetAt(i);
    	//获取首行
    	XSSFRow title = sheet.getRow(0);
    	
    	for(int j = 1; j < sheet.getPhysicalNumberOfRows(); j ++){
    		//获取单行
    		XSSFRow row = sheet.getRow(j);
    		//获取单个单元格
    		XSSFCell cell= row.getCell(0);
    		//设置单元格格式
    		cell.setCellType(CellType.STRING);
    		
    		...对单元格进行操作
	    }
    }