在这里插入图片描述

1 问题背景

2 前言

3 实现思路

后端查询要导出的数据，此处简称data
使用阿里的EasyExcel组件将data写到HttpServletResponse里面，返回指定的响应头、响应内容的类型、字符编码。响应出去的数据是二进制数据，此处简称bytes数据
前端使用前端框架提供的方法，将 bytes数据转成blob，然后生成下载地址，然后进行下载

4 后端实现

<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>easyexcel</artifactId>
			<version>2.1.7</version>
		</dependency>

@Data
public class UserInfoVO {
  @ExcelProperty(value = "用户ID",index = 0)
  private Long id;
  @ExcelProperty(value = "用户姓名",index = 1)
  private String username;
  @ExcelProperty(value = "性别",index = 2)
  private String sex;
}

  @PostMapping("/xx/xxx/xxx")
  public void export(HttpServletResponse reponse) {
        // 设置响应头等
        response.setHeader("Content-Disposition", "attachment;filename=" + "文件名(随便定义).xlsx");
        response.setContentType("application/vnd.ms-excel");
        response.setCharacterEncoding("UTF-8");

        // 查数据，假如要导出UserInfo的列表信息
        List<UserInfoVO> data = selectData();
       // 导出数据 
       EasyExcel.write(response.getOutputStream()).head(UserInfoVO.class).sheet().doWrite(data);
  }

5 设置Excel自适应列宽

public class CustomCellWriteWeightConfig extends AbstractColumnWidthStyleStrategy {

    private Map<Integer, Map<Integer, Integer>> CACHE = new HashMap<>();

    @Override
    protected void setColumnWidth(WriteSheetHolder writeSheetHolder, List<CellData> cellDataList, Cell cell, Head head, Integer integer, Boolean isHead) {
        boolean needSetWidth = isHead || !CollectionUtils.isEmpty(cellDataList);
        if (needSetWidth) {
            Map<Integer, Integer> maxColumnWidthMap = CACHE.get(writeSheetHolder.getSheetNo());
            if (maxColumnWidthMap == null) {
                maxColumnWidthMap = new HashMap<>();
                CACHE.put(writeSheetHolder.getSheetNo(), maxColumnWidthMap);
            }

            Integer columnWidth = this.dataLength(cellDataList, cell, isHead);
            if (columnWidth >= 0) {
                if (columnWidth > 254) {
                    columnWidth = 254;
                }

                Integer maxColumnWidth = maxColumnWidthMap.get(cell.getColumnIndex());
                if (maxColumnWidth == null || columnWidth > maxColumnWidth) {
                    maxColumnWidthMap.put(cell.getColumnIndex(), columnWidth);
                    Sheet sheet = writeSheetHolder.getSheet();
                    sheet.setColumnWidth(cell.getColumnIndex(), columnWidth * 256);
                }

            }
        }
    }

    /**
     * 计算长度
     * @param cellDataList
     * @param cell
     * @param isHead
     * @return
     */
    private Integer dataLength(List<CellData> cellDataList, Cell cell, Boolean isHead) {
        if (isHead) {
            return cell.getStringCellValue().getBytes().length;
        } else {
            CellData cellData = cellDataList.get(0);
            CellDataTypeEnum type = cellData.getType();
            if (type == null) {
                return -1;
            } else {
                switch (type) {
                    case STRING:
                        // 换行符（数据需要提前解析好）
                        int index = cellData.getStringValue().indexOf("\n");
                        return index != -1 ?
                                cellData.getStringValue().substring(0, index).getBytes().length + 1 : cellData.getStringValue().getBytes().length + 1;
                    case BOOLEAN:
                        return cellData.getBooleanValue().toString().getBytes().length;
                    case NUMBER:
                        return cellData.getNumberValue().toString().getBytes().length;
                    default:
                        return -1;
                }
            }
        }
    }
}

EasyExcel.write(response.getOutputStream())
                    .head(SubscriptionOrderExportResp.class)
                    //  注册自适应列宽组件
                    .registerWriteHandler(new CustomCellWriteWeightConfig())
                    .sheet()
                    .doWrite(data);