Vue中实现自定义excel下载

目录

第一种：后端生成excel

第二种：前端合成excel

总结

参考资料

---

最近在工作中遇到一个需求，就是需要在前端实现一个错误模板Excel的下载功能。

实现下载有两种方式，一种是后端生成一个excel，放在服务器指定目录下，然后前端直接去后端拿。第二种是后端传给前端一个json的list，前端用后端传过来的json的list直接在前端合成一个excel。

第一种：后端生成excel

java后端生成excel代码

生成excel工具方法

/**
     * @author: wu linchun
     * @creat: 2021-07-29 9:49
     * @desc: 将list集合转成Excel文件
     * list: 内容list
     * path: 上传的excel路径
     * fileName: 上传的excel名称
     **/
    public static String createExcel(List<? extends Object> list, String path, String fileName) {
        String result = "";
        if (list.size() == 0 || list == null) {
            result = "没有对象信息";
        } else {
            Object o = list.get(0);
            Class<? extends Object> clazz = o.getClass();
            String className = clazz.getSimpleName();
            //这里通过反射获取字段数组
            Field[] fields = clazz.getDeclaredFields();
            File folder = new File(path);
            if (!folder.exists()) {
                folder.mkdirs();
            }
            String name = fileName.concat(".xls");
            WritableWorkbook book = null;
            File file = null;
            try {
                file = new File(path.concat(File.separator).concat(name));
                //创建xls文件
                book = jxl.Workbook.createWorkbook(file);
                WritableSheet sheet = book.createSheet(className, 0);
                //列
                int i = 0;
                //行
                int j = 0;
                for (Field f : fields) {
                    j = 0;
                    //这里把字段名称写入excel第一行中
                    Label label = new Label(i, j, f.getName());
                    sheet.addCell(label);
                    j = 1;
                    for (Object obj : list) {
                        Object temp = getFieldValueByName(f.getName(), obj);
                        String strTemp = "";
                        if (temp != null) {
                            strTemp = temp.toString();
                        }
                        //把每个对象此字段的属性写入这一列excel中
                        sheet.addCell(new Label(i, j, strTemp));
                        j++;
                    }
                    i++;
                }
                book.write();
                result = file.getPath();
            } catch (Exception e) {
                // TODO Auto-generated catch block
                result = "SystemException";
                e.printStackTrace();
            } finally {
                fileName = null;
                name = null;
                folder = null;
                file = null;
                if (book != null) {
                    try {
                        book.close();
                    } catch (WriteException e) {
                        // TODO Auto-generated catch block
                        result = "WriteException";
                        e.printStackTrace();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        result = "IOException";
                        e.printStackTrace();
                    }
                }
            }
        }
        //最后输出文件路径
        return result;
    }

下载文件

 /**
     * @author: wu linchun
     * @creat: 2021-07-29 13:28
     * @desc: 下载错误模板
     **/
    @Override
    public ResponseEntity<Object> downloadErrorModel() throws FileNotFoundException {
        // 这里的fileName是指路径+文件名
        String fileName="move_cms/src/main/resources/static/errorList.xls";
        File file = new File(fileName);
        InputStreamResource resource = new InputStreamResource(new FileInputStream((file)));
        org.springframework.http.HttpHeaders headers = new org.springframework.http.HttpHeaders();
        headers.add("Content-Disposition", String.format("attachment;filename=\"%s\"", file.getName()));
        headers.add("Cache-Control", "no-cache,no-store,must-revalidate");
        headers.add("Pragma", "no-cache");
        headers.add("Expires", "0");

        ResponseEntity<Object> responseEntity = ResponseEntity.ok()
                .headers(headers)
                .contentLength(file.length())
                .contentType(MediaType.parseMediaType("application/text"))
                .body(resource);
        return responseEntity;
    }

下载excel的接口

 /**
     * @author: wu linchun
     * @creat: 2021-07-29 11:41
     * @desc: 下载错误模板
     **/
    @ApiOperation(value = "下载错误模板")
    @GetMapping(value = "/downloadErrorModel")
    @PassToken
    public ResponseEntity<Object> downloadErrorModel() throws FileNotFoundException {
        System.out.println("下载错误模板");
        return welfareGrantService.downloadErrorModel();
    }

在掉/downloadErrorModel这个接口是要注意，只能用超链接 “<a:href />调用，不能使用axios调这个接口。这是由于axios获取的是json

而这个接口返回的是file类型，file会以byte流的形式在http上面传输，因此调/downloadErrorModel这个接口将会接收到byte流，axios默认是接收不了byte的，需要进行一些特殊的设置。可以参考一下这篇：vue使用axios接收流文件_weixin_43869439的博客-CSDN博客

如果使用超链接的方式访问接口进行文件下载的话，则需要获取到后端服务器的ip+port（实际中不建议这么做，因为get请求会暴露ip地址和端口，可通过浏览器f12看到ip地址和端口，不安全）

ip地址可通过 InetAddress.getLocalHost()获取到，端口号直接用@Value从配置文件中拿到。

第二种：前端合成excel

在vue工程中引入两个依赖：file-saver和xlsx

使用“npm install”，安装package.json中新增的依赖

npm install

新增 ExportExcelUtil.js，用来根据list生成excel

/* eslint-disable */
import { saveAs } from 'file-saver'
import XLSX from 'xlsx'

function generateArray(table) {
  var out = [];
  var rows = table.querySelectorAll('tr');
  var ranges = [];
  for (var R = 0; R < rows.length; ++R) {
    var outRow = [];
    var row = rows[R];
    var columns = row.querySelectorAll('td');
    for (var C = 0; C < columns.length; ++C) {
      var cell = columns[C];
      var colspan = cell.getAttribute('colspan');
      var rowspan = cell.getAttribute('rowspan');
      var cellValue = cell.innerText;
      if (cellValue !== "" && cellValue == +cellValue) cellValue = +cellValue;

      //Skip ranges
      ranges.forEach(function (range) {
        if (R >= range.s.r && R <= range.e.r && outRow.length >= range.s.c && outRow.length <= range.e.c) {
          for (var i = 0; i <= range.e.c - range.s.c; ++i) outRow.push(null);
        }
      });

      //Handle Row Span
      if (rowspan || colspan) {
        rowspan = rowspan || 1;
        colspan = colspan || 1;
        ranges.push({
          s: {
            r: R,
            c: outRow.length
          },
          e: {
            r: R + rowspan - 1,
            c: outRow.length + colspan - 1
          }
        });
      };

      //Handle Value
      outRow.push(cellValue !== "" ? cellValue : null);

      //Handle Colspan
      if (colspan)
        for (var k = 0; k < colspan - 1; ++k) outRow.push(null);
    }
    out.push(outRow);
  }
  return [out, ranges];
};

function datenum(v, date1904) {
  if (date1904) v += 1462;
  var epoch = Date.parse(v);
  return (epoch - new Date(Date.UTC(1899, 11, 30))) / (24 * 60 * 60 * 1000);
}

function sheet_from_array_of_arrays(data, opts) {
  var ws = {};
  var range = {
    s: {
      c: 10000000,
      r: 10000000
    },
    e: {
      c: 0,
      r: 0
    }
  };
  for (var R = 0; R != data.length; ++R) {
    for (var C = 0; C != data[R].length; ++C) {
      if (range.s.r > R) range.s.r = R;
      if (range.s.c > C) range.s.c = C;
      if (range.e.r < R) range.e.r = R;
      if (range.e.c < C) range.e.c = C;
      var cell = {
        v: data[R][C]
      };
      if (cell.v == null) continue;
      var cell_ref = XLSX.utils.encode_cell({
        c: C,
        r: R
      });

      if (typeof cell.v === 'number') cell.t = 'n';
      else if (typeof cell.v === 'boolean') cell.t = 'b';
      else if (cell.v instanceof Date) {
        cell.t = 'n';
        cell.z = XLSX.SSF._table[14];
        cell.v = datenum(cell.v);
      } else cell.t = 's';

      ws[cell_ref] = cell;
    }
  }
  if (range.s.c < 10000000) ws['!ref'] = XLSX.utils.encode_range(range);
  return ws;
}

function Workbook() {
  if (!(this instanceof Workbook)) return new Workbook();
  this.SheetNames = [];
  this.Sheets = {};
}

function s2ab(s) {
  var buf = new ArrayBuffer(s.length);
  var view = new Uint8Array(buf);
  for (var i = 0; i != s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
  return buf;
}

export function export_table_to_excel(id) {
  var theTable = document.getElementById(id);
  var oo = generateArray(theTable);
  var ranges = oo[1];

  /* original data */
  var data = oo[0];
  var ws_name = "SheetJS";

  var wb = new Workbook(),
    ws = sheet_from_array_of_arrays(data);

  /* add ranges to worksheet */
  // ws['!cols'] = ['apple', 'banan'];
  ws['!merges'] = ranges;

  /* add worksheet to workbook */
  wb.SheetNames.push(ws_name);
  wb.Sheets[ws_name] = ws;

  var wbout = XLSX.write(wb, {
    bookType: 'xlsx',
    bookSST: false,
    type: 'binary'
  });

  saveAs(new Blob([s2ab(wbout)], {
    type: "application/octet-stream"
  }), "test.xlsx")
}

export function export_json_to_excel({
  multiHeader = [],
  header,
  data,
  filename,
  merges = [],
  autoWidth = true,
  bookType = 'xlsx'
} = {}) {
  /* original data */
  filename = filename || 'excel-list'
  data = [...data]
  data.unshift(header);

  for (let i = multiHeader.length - 1; i > -1; i--) {
    data.unshift(multiHeader[i])
  }

  var ws_name = "SheetJS";
  var wb = new Workbook(),
    ws = sheet_from_array_of_arrays(data);

  if (merges.length > 0) {
    if (!ws['!merges']) ws['!merges'] = [];
    merges.forEach(item => {
      ws['!merges'].push(XLSX.utils.decode_range(item))
    })
  }

  if (autoWidth) {
    /*设置worksheet每列的最大宽度*/
    const colWidth = data.map(row => row.map(val => {
      /*先判断是否为null/undefined*/
      if (val == null) {
        return {
          'wch': 10
        };
      }
      /*再判断是否为中文*/
      else if (val.toString().charCodeAt(0) > 255) {
        return {
          'wch': val.toString().length * 2
        };
      } else {
        return {
          'wch': val.toString().length
        };
      }
    }))
    /*以第一行为初始值*/
    let result = colWidth[0];
    for (let i = 1; i < colWidth.length; i++) {
      for (let j = 0; j < colWidth[i].length; j++) {
        if (result[j]['wch'] < colWidth[i][j]['wch']) {
          result[j]['wch'] = colWidth[i][j]['wch'];
        }
      }
    }
    ws['!cols'] = result;
  }

  /* add worksheet to workbook */
  wb.SheetNames.push(ws_name);
  wb.Sheets[ws_name] = ws;

  var wbout = XLSX.write(wb, {
    bookType: bookType,
    bookSST: false,
    type: 'binary'
  });
  saveAs(new Blob([s2ab(wbout)], {
    type: "application/octet-stream"
  }), `${filename}.${bookType}`);
}

在.vue中添加下载excel方法

// 下载Excel
    downloadExcel () {
      import('@/utils/ExportExcelUtil').then(excel => {
        const filterVal = ['item', 'error']
        const tHeader = ['item', 'error']
        const data = this.formatModelJson(filterVal, this.errList)
        console.log(data)
        console.info(data)
        excel.export_json_to_excel({
          header: tHeader,
          data,
          filename: 'errorList'
        })
      })
    },
    // 格式化JSON
    formatModelJson (filterVal, list) {
      return list.map(v => filterVal.map(j => {
        return v[j]
      }))
    },

errorList是从后端传过来的

exportExcel () {
      getErrorListExcel().then(response => {
        this.errList = response.data
      })
    }

使用created方法，在加载.vue时，就调用/getErrorListExcel接口，获取errorList的值。

created () {
    this.exportExcel()
  },

调用后端接口的api

import axios from 'axios'

export function getErrorListExcel () {
  return axios.get('http://127.0.0.1:8082/login/getErrorListExcel', {
  }).then(response => response).catch(error => error)
}

后端接口设置errorList中的值

 @GetMapping("/getErrorListExcel")
    public List<ErrorItemBO> getErrorListExcel() {
        List<ErrorItemBO> list = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            ErrorItemBO errorItemBO = new ErrorItemBO();
            errorItemBO.setItem("item" + i);
            errorItemBO.setError("error" + i);
            list.add(errorItemBO);
        }
        return list;
    }

总结

如果涉及到文件下载，尽量后端传一个list，然后都在前端合成相应的文件以到达减轻服务器负担的作用。

参考资料

文件上传下载原理：http协议分析及实现 - 等你归去来 - 博客园 (cnblogs.com)