<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>3.17</version>
</dependency>

implementation group: 'org.apache.poi', name: 'poi', version: '3.17'

@Retention(value = RetentionPolicy.RUNTIME)
@Target(value = ElementType.FIELD)
public @interface Excel {
    String name();//列的名字

    int width() default 6000;//列的寬度

    int index() default -1;//決定生成的順序

    boolean isMust() default true; // 是否為必須值,默認(rèn)是必須的
}

public class GoodsExcelModel {
    @Excel(name = "ID_禁止改動", index = 0, width = 0)
    private Long picId;//picId
    @Excel(name = "產(chǎn)品ID_禁止改動", index = 1, width = 0)
    private Long productId;
    @Excel(name = "型號", index = 3)
    private String productName;//產(chǎn)品型號
    @Excel(name = "系列", index = 2)
    private String seriesName;//系列名字
    @Excel(name = "庫存", index = 5)
    private Long quantity;
    @Excel(name = "屬性值", index = 4)
    private String propValue;
    @Excel(name = "價格", index = 6)
    private Double price;
    @Excel(name = "商品編碼", index = 7, isMust = false)
    private String outerId;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long dbId; // 數(shù)據(jù)庫自增長id

    private Date createTime; // 記錄創(chuàng)建時間
 }

public class ExcelUtil {
    private static final String GET = "get";
    private static final String SET = "set";
    private static Logger logger = LoggerFactory.getLogger(ExcelUtil.class);

    /**
     * 將對象轉(zhuǎn)換成Excel
     *
     * @param objList 需要轉(zhuǎn)換的對象
     * @return 返回是poi中的對象
     */
    public static HSSFWorkbook toExcel(List objList) {
        if (CollectionUtils.isEmpty(objList)) throw new NullPointerException("無效的數(shù)據(jù)");
        Class aClass = objList.get(0).getClass();
        Field[] fields = aClass.getDeclaredFields();
        HSSFWorkbook workbook = new HSSFWorkbook();
        HSSFSheet sheet = workbook.createSheet();
        for (int i = 0; i < objList.size(); i++) {
            HSSFRow row = sheet.createRow(i + 1);//要從第二行開始寫
            HSSFRow topRow = null;
            if (i == 0) topRow = sheet.createRow(0);
            for (Field field : fields) {
                Excel excel = field.getAnnotation(Excel.class);//得到字段是否使用了Excel注解
                if (excel == null) continue;
                HSSFCell cell = row.createCell(excel.index());//設(shè)置當(dāng)前值放到第幾列
                String startName = field.getName().substring(0, 1);
                String endName = field.getName().substring(1, field.getName().length());
                String methodName = new StringBuffer(GET).append(startName.toUpperCase()).append(endName).toString();
                try {
                    Method method = aClass.getMethod(methodName);//根據(jù)方法名獲取方法,用于調(diào)用
                    Object invoke = method.invoke(objList.get(i));
                    if (invoke == null) continue;
                    cell.setCellValue(invoke.toString());
                } catch (NoSuchMethodException e) {
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                } catch (InvocationTargetException e) {
                    e.printStackTrace();
                }
                if (topRow == null) continue;
                HSSFCell topRowCell = topRow.createCell(excel.index());
                topRowCell.setCellValue(excel.name());
                sheet.setColumnWidth(excel.index(), excel.width());
            }
        }

        return workbook;
    }

    /**
     * 將Excel文件轉(zhuǎn)換為指定對象
     *
     * @param file 傳入的Excel
     * @param c    需要被指定的class
     * @return
     * @throws IOException
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
    public static <T> List<T> excelFileToObject(MultipartFile file, Class<T> c) throws IOException, IllegalAccessException, InstantiationException {
        //key為反射得到的下標(biāo),value為對于的set方法
        Map<Integer, String> methodMap = new HashMap<>();
        //保存第一列的值與對應(yīng)的下標(biāo),用于驗(yàn)證用戶是否刪除了該列,key為下標(biāo),value為名字
        Map<Integer, String> startRowNameMap = new HashMap<>();
        //用來記錄當(dāng)前參數(shù)是否為必須的
        Map<Integer, Boolean> fieldIsMustMap = new HashMap<>();
        //得到所有的字段
        Field[] fields = c.getDeclaredFields();
        for (Field field : fields) {
            Excel excel = field.getAnnotation(Excel.class);
            if (excel == null) continue;
            String startName = field.getName().substring(0, 1);
            String endName = field.getName().substring(1, field.getName().length());
            String methodName = new StringBuffer(SET).append(startName.toUpperCase()).append(endName).toString();
            methodMap.put(excel.index(), methodName);
            startRowNameMap.put(excel.index(), excel.name());
            fieldIsMustMap.put(excel.index(), excel.isMust());
        }

        String fileName = file.getOriginalFilename();
        Workbook wb = fileName.endsWith(".xlsx") ? new XSSFWorkbook(file.getInputStream()) : new HSSFWorkbook(file.getInputStream());
        Sheet sheet = wb.getSheetAt(0);
        Row sheetRow = sheet.getRow(0);
        for (Cell cell : sheetRow) {
            Integer columnIndex = cell.getColumnIndex();
            if (cell.getCellTypeEnum() != CellType.STRING) throw new ExcelException("excel校驗(yàn)失敗, 請勿刪除文件中第一行數(shù)據(jù) !!!");
            String value = cell.getStringCellValue();
            String name = startRowNameMap.get(columnIndex);
            if (name == null) throw new ExcelException("excel校驗(yàn)失敗,請勿移動文件中任何列的順序!!!");
            if (!name.equals(value)) throw new ExcelException("excel校驗(yàn)失敗,【" + name + "】列被刪除,請勿刪除文件中任何列 !!!");
        }
        sheet.removeRow(sheetRow);//第一行是不需要被反射賦值的
        List<T> models = new ArrayList<>();
        for (Row row : sheet) {
            if (row == null || !checkRow(row)) continue;
            T obj = c.newInstance();//創(chuàng)建新的實(shí)例化對象
            Class excelModelClass = obj.getClass();
            startRowNameMap.entrySet().forEach(x -> {
                Integer index = x.getKey();
                Cell cell = row.getCell(index);
                String methodName = methodMap.get(index);
                if (StringUtils.isEmpty(methodName)) return;
                List<Method> methods = Lists.newArrayList(excelModelClass.getMethods()).stream()
                        .filter(m -> m.getName().startsWith(SET)).collect(Collectors.toList());
                String rowName = startRowNameMap.get(index);//列的名字
                for (Method method : methods) {
                    if (!method.getName().startsWith(methodName)) continue;
                    //檢測value屬性
                    String value = valueCheck(cell, rowName, fieldIsMustMap.get(index));
                    //開始進(jìn)行調(diào)用方法反射賦值
                    methodInvokeHandler(obj, method, value);
                }
            });
            models.add(obj);
        }
        return models;
    }

    /**
     * 檢測當(dāng)前需要賦值的value
     *
     * @param cell    當(dāng)前循環(huán)行中的列對象
     * @param rowName 列的名字{@link Excel}中的name
     * @param isMust  是否為必須的
     * @return 值
     */
    private static String valueCheck(Cell cell, String rowName, Boolean isMust) {
        //有時候刪除單個數(shù)據(jù)會造成cell為空,也可能是value為空
        if (cell == null && isMust) {
            throw new ExcelException("excel校驗(yàn)失敗,【" + rowName + "】中的數(shù)據(jù)禁止單個刪除");
        }
        if (cell == null) return null;
        cell.setCellType(CellType.STRING);
        String value = cell.getStringCellValue();
        if ((value == null || value.trim().isEmpty()) && isMust) {
            throw new ExcelException("excel校驗(yàn)失敗,【" + rowName + "】中的數(shù)據(jù)禁止單個刪除");
        }
        return value;
    }

    /**
     * 反射賦值的處理的方法
     *
     * @param obj      循環(huán)創(chuàng)建的需要賦值的對象
     * @param method 當(dāng)前對象期中一個set方法
     * @param value  要被賦值的內(nèi)容
     */
    private static void methodInvokeHandler(Object obj, Method method, String value) {
        Class<?> parameterType = method.getParameterTypes()[0];
        try {
            if (parameterType == null) {
                method.invoke(obj);
                return;
            }
            String name = parameterType.getName();
            if (name.equals(String.class.getName())) {
                method.invoke(obj, value);
                return;
            }
            if (name.equals(Long.class.getName())) {
                method.invoke(obj, Long.valueOf(value));
                return;
            }
            if (name.equals(Double.class.getName())) {
                method.invoke(obj, Double.valueOf(value));
            }

        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

    private static boolean checkRow(Row row) {
        try {
            if (row == null) return false;
            short firstCellNum = row.getFirstCellNum();
            short lastCellNum = row.getLastCellNum();
            if (firstCellNum < 0 && lastCellNum < 0) return false;
            if (firstCellNum != 0) {
                for (short i = firstCellNum; i < lastCellNum; i++) {
                    Cell cell = row.getCell(i);
                    String cellValue = cell.getStringCellValue();
                    if (!StringUtils.isBlank(cellValue)) return true;
                }
                return false;
            }
            return true;
        } catch (Exception e) {
            return true;
        }

    }