目录

一、安装插件

二、Export2Excel.js

三、Vue导出Excel代码

四、导出数据的获得 （后端）

4.1 DownLoad.java

 4.2 DownLoadController.java

4.3 DownLoadMapper.java

五、错误解决

六、导出结果

前言：本篇博客主要记录课程管理-导出成绩到Excel表格的功能。即在vue中把数据导出成Excel格式的文件。

一、安装插件

npm install -S file-saver xlsx
npm install -D script-loader

二、Export2Excel.js

在src的目录下面加一个excel的文件夹，在excel的文件里面新建一个Export2Excel.js的文件。

Export2Excel.js代码 如下：

require('script-loader!file-saver');
import XLSX from 'xlsx-style'

function generateArray(table) {
    console.log(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;

            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);
                }
            });

            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
                    }
                });
            };

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

            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];

    var data = oo[0];
    var ws_name = "SheetJS";

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

    ws['!merges'] = ranges;

    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'
                                     } = {}) {
    
    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) {
        
        const colWidth = data.map(row => row.map(val => {
            
            if (val == null) {
                return {
                    'wch': 10
                };
            }
            
            else if (val.toString().charCodeAt(0) > 255) {
                return {
                    'wch': val.toString().length * 2
                };
            } else {
                return {
                    'wch': val.toString().length
                };
            }
        }))
        
        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;
    }

    
    wb.SheetNames.push(ws_name);
    wb.Sheets[ws_name] = ws;
    var dataInfo = wb.Sheets[wb.SheetNames[0]];

    const borderAll = {  //单元格外侧框线
        top: {
            style: 'thin'
        },
        bottom: {
            style: 'thin'
        },
        left: {
            style: 'thin'
        },
        right: {
            style: 'thin'
        }
    };
    //给所以单元格加上边框
    for (var i in dataInfo) {
        if (i == '!ref' || i == '!merges' || i == '!cols' || i == 'A1') {
        } else {
            dataInfo[i + ''].s = {
                border: borderAll
            }
        }
    }

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

三、Vue导出Excel代码

    download(){
      console.log(this.currentcourse)
      request.get("/download/load",{
        params:{
          courseid:this.currentcourse,
        }
      }).then(res =>{
        console.log(res.data)
        this.Export2Excel(res.data)
      })
    },

    Export2Excel(dataList) {
      // 这个引入路径就是你刚才创建的那个文件
      import('../excel/Export2Excel').then(excel => {
        const tHeader = ['学号', '姓名', '题目','完成时间']
        // const title = ['', '', '','']; // 这个title和上面数组的数量必须是一致的但是可以是空的
        // 表头对应字段
        const filterVal =['username', 'realname', 'problemname','finishtime'];
        const list = dataList
        const data = this.formatJson(filterVal, list)
          data.map(item => {
            // console.log(item)
            item.map((i, index) => {
              if (!i) {
                item[index] = ''
              }
            })
          })
          // const merges = ['A1:D1'] //合并单元格
          excel.export_json_to_excel({
            // title: title,
            header: tHeader,
            data,
            // merges,
            filename: this.currentcoursename,
            autoWidth: true,
            bookType: 'xlsx'
          })
      })
    },

    formatJson(filterVal, jsonData) {
      return jsonData.map((v) => filterVal.map((j) => v[j]));
    },

四、导出数据的获得 （后端）

4.1 DownLoad.java

导出数据需要四个属性：学号、姓名、题目、完成时间

因此，建立实体类DownLoad.java

package com.sducsrp.csrp.entity;

import lombok.Data;

@Data
public class DownLoad {
    private String username;
    private String realname;
    private String problemname;
    private String finishtime;
}

 4.2 DownLoadController.java

@RestController
@RequestMapping("/download")
public class DownLoadController {

    @Resource
    DownLoadMapper downLoadMapper;

    @GetMapping("/load")
    public Result download(@RequestParam() Integer courseid){
        List downLoads=downLoadMapper.sel(courseid);
        return Result.success(downLoads);
    }
}

4.3 DownLoadMapper.java

查询所需属性需要自然连接四个表，SQL语句为：

    @Select("select username,realname, problemname,finishtime from stucourse NATURAL JOIN user NATURAL JOIN stuproblem NATURAL JOIN problem where stucourse.courseid=#{courseid}")
    List sel(Integer courseid);

五、错误解决

代码写完后，前端编译报错：

* ./cptable in ./node_modules/xlsx-style/dist/cpexcel.js

出现上述原因是因为Excel文件导出时所用的xlsx-style库错误所导致的，这是需要改安装依赖的文件内容，根据提示找到该js文件在807行做修改。将var cpt = require(’./cpt’ + ‘able’)改成var cpt = cptable就可以了。

六、导出结果