快速学习POI-自定义工具类

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface ExcelAttribute {
    /** 对应的列名称 */
    String name() default "";
    /** 列序号 */
    int sort();
    /** 字段类型对应的格式 */
    String format() default ""; }

@Getter
@Setter
public class ExcelExportUtil<T> {
    private int rowIndex;
    private int styleIndex;
    private String templatePath;
    private Class clazz;
    private  Field fields[];
    public ExcelExportUtil(Class clazz,int rowIndex,int styleIndex) {
        this.clazz = clazz;
        this.rowIndex = rowIndex;
        this.styleIndex = styleIndex;
        fields = clazz.getDeclaredFields();
   }
    /**
     * 基于注解导出
     */
    public void export(HttpServletResponse response,InputStream is, List<T> objs,String
fileName) throws Exception {
        XSSFWorkbook workbook = new XSSFWorkbook(is);
        Sheet sheet = workbook.getSheetAt(0);
        CellStyle[] styles = getTemplateStyles(sheet.getRow(styleIndex));
        AtomicInteger datasAi = new AtomicInteger(rowIndex);
        for (T t : objs) {
            Row row = sheet.createRow(datasAi.getAndIncrement());
            for(int i=0;i<styles.length;i++) {
                Cell cell = row.createCell(i);
                cell.setCellStyle(styles[i]);
                for (Field field : fields) {
                    if(field.isAnnotationPresent(ExcelAttribute.class)){
                        field.setAccessible(true);
                        ExcelAttribute ea = field.getAnnotation(ExcelAttribute.class);
                        if(i == ea.sort()) {
                            cell.setCellValue(field.get(t).toString());
                       }
                   }
               }
           }
       }
        fileName = URLEncoder.encode(fileName, "UTF-8");
        response.setContentType("application/octet-stream");
        response.setHeader("content-disposition", "attachment;filename=" + new
String(fileName.getBytes("ISO8859-1")));
        response.setHeader("filename", fileName);
        workbook.write(response.getOutputStream());
   }
    public CellStyle[] getTemplateStyles(Row row) {
        CellStyle [] styles = new CellStyle[row.getLastCellNum()];
        for(int i=0;i<row.getLastCellNum();i++) {
            styles[i] = row.getCell(i).getCellStyle();
       }
        return styles;
   }
}

public class ExcelImportUtil<T> {
    private Class clazz;
    private  Field fields[];
    public ExcelImportUtil(Class clazz) {
        this.clazz = clazz;
        fields = clazz.getDeclaredFields();
   }
    /**
     * 基于注解读取excel
     */
    public List<T> readExcel(InputStream is, int rowIndex,int cellIndex) {
        List<T> list = new ArrayList<T>();
        T entity = null;
        try {
            XSSFWorkbook workbook = new XSSFWorkbook(is);
            Sheet sheet = workbook.getSheetAt(0);
            // 不准确
            int rowLength = sheet.getLastRowNum();
            System.out.println(sheet.getLastRowNum());
            for (int rowNum = rowIndex; rowNum <= sheet.getLastRowNum(); rowNum++) {
                Row row = sheet.getRow(rowNum);
                entity = (T) clazz.newInstance();
                System.out.println(row.getLastCellNum());
                for (int j = cellIndex; j < row.getLastCellNum(); j++) {
                    Cell cell = row.getCell(j);
                    for (Field field : fields) {
                        if(field.isAnnotationPresent(ExcelAttribute.class)){
                            field.setAccessible(true);
                            ExcelAttribute ea =
field.getAnnotation(ExcelAttribute.class);
                            if(j == ea.sort()) {
                                field.set(entity, covertAttrType(field, cell));
                           }
                       }
                   }
               }
                list.add(entity);
           }
       } catch (Exception e) {
            e.printStackTrace();
       }
        return list;
   }
    /**
     * 类型转换 将cell 单元格格式转为 字段类型
     *  */
    private Object covertAttrType(Field field, Cell cell) throws Exception {
        String fieldType = field.getType().getSimpleName();
        if ("String".equals(fieldType)) {
            return getValue(cell);
       }else if ("Date".equals(fieldType)) {
            return new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").parse(getValue(cell)) ;
       }else if ("int".equals(fieldType) || "Integer".equals(fieldType)) {
            return Integer.parseInt(getValue(cell));
       }else if ("double".equals(fieldType) || "Double".equals(fieldType)) {
            return Double.parseDouble(getValue(cell));
       }else {
            return null;
       }
   }
    /**
     * 格式转为String
     * @param cell
     * @return
     */
    public String getValue(Cell cell) {
        if (cell == null) {
            return "";
       }
        switch (cell.getCellType()) {
            case STRING:
                return cell.getRichStringCellValue().getString().trim();
            case NUMERIC:
                if (DateUtil.isCellDateFormatted(cell)) {
                    Date dt = DateUtil.getJavaDate(cell.getNumericCellValue());
                    return new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(dt);
               } else {
                    // 防止数值变成科学计数法
                    String strCell = "";
                    Double num = cell.getNumericCellValue();
                    BigDecimal bd = new BigDecimal(num.toString());
                    if (bd != null) {
                        strCell = bd.toPlainString();
                   }
                    // 去除 浮点型 自动加的 .0
                    if (strCell.endsWith(".0")) {
                        strCell = strCell.substring(0, strCell.indexOf("."));
                   }
                    return strCell;
               }
            case BOOLEAN:
                return String.valueOf(cell.getBooleanCellValue());
            default:
                return "";
       }
   }
}

List<User> list = new ExcelImportUtil(User.class).readExcel(is, 1, 2);

  @RequestMapping(value = "/export/{month}", method = RequestMethod.GET)
    public void export(@PathVariable(name = "month") String month) throws Exception {
        //1.构造数据
        List<EmployeeReportResult> list =
userCompanyPersonalService.findByReport(companyId,month+"%");
        //2.加载模板流数据
        Resource resource = new ClassPathResource("excel-template/hr-demo.xlsx");
        FileInputStream fis = new FileInputStream(resource.getFile());
        new ExcelExportUtil(EmployeeReportResult.class,2,2).
                export(response,fis,list,"人事报表.xlsx");
   }