踹掉后端，前端导出Excel！

　　前言

　　导出Excel文件这个功能，通常都是在后端实现返回前端一个下载链接，但有时候我们只想导出前端页面上已经有了的数据，不想再调后端导出接口浪费服务器资源，学习本文demo例子，我们踹掉后端，直接在前端导出Excel！

 

　　代码实现

　　1、利用Blob对象构造一个a标签的href链接，从而实现文件下载，Excel支持html格式，因此我们只需要将构造好的html内容放到Blob对象中，即可下载Excel表格

　　2、利用base64编码构造一个a标签的href链接，从而实现文件下载，同上，我们需要将构造好的html内容URI编码拼到base64链接，即可下载Excel表格

    //blob、base64转文件下载，通过A标签模拟点击,设置文件名    /*        万能流  application/octet-stream        word文件  application/msword        excel文件  application/vnd.ms-excel        txt文件  text/plain        图片文件  image/png、jpeg、gif、bmp     */    function downloadByBlob(fileName, text) {        let a = document.createElement("a");        a.href = URL.createObjectURL(new Blob([text], {type: "application/octet-stream"}));        a.download = fileName || 'Blob导出测试.txt';        a.click();        a.remove();        URL.revokeObjectURL(a.href);    }    function downloadByBase64(fileName, text) {        let a = document.createElement('a');        a.href = 'data:application/octet-stream;base64,' + window.btoa(unescape(encodeURIComponent(text)));        a.download = fileName || 'Base64导出测试.txt';        a.click();        a.remove();        URL.revokeObjectURL(a.href);    }

　　封装导出Excel表格方法

    //踹掉后端，前端导出Excel！    function exportExcel(fileName,columns,datas){        //列名        let columnHtml = "";        columnHtml += "<tr style=\"text-align: center;\">\n";        for (let key in columns) {            columnHtml += "<td style=\"background-color:#bad5fd\">"+columns[key]+"</td>\n";        }        columnHtml += "</tr>\n";        //数据        let dataHtml = "";        for (let data of datas) {            dataHtml += "<tr style=\"text-align: center;\">\n";            for (let key in columns) {                dataHtml += "<td>"+data[key]+"</td>\n";            }            dataHtml += "</tr>\n";        }        //完整html        let excelHtml = "<html xmlns:o=\"urn:schemas-microsoft-com:office:office\"\n" +            "      xmlns:x=\"urn:schemas-microsoft-com:office:excel\"\n" +            "      xmlns=\"http://www.w3.org/TR/REC-html40\">\n" +            "<head>\n" +            "   <!-- 加这个，其他单元格带边框 -->" +            "   <xml>\n" +            "        <x:ExcelWorkbook>\n" +            "            <x:ExcelWorksheets>\n" +            "                <x:ExcelWorksheet>\n" +            "                    <x:Name></x:Name>\n" +            "                    <x:WorksheetOptions>\n" +            "                        <x:DisplayGridlines/>\n" +            "                    </x:WorksheetOptions>\n" +            "                </x:ExcelWorksheet>\n" +            "            </x:ExcelWorksheets>\n" +            "        </x:ExcelWorkbook>\n" +            "   </xml>\n" +            "   <style>td{font-family: \"宋体\";}</style>\n" +            "</head>\n" +            "<body>\n" +            "<table border=\"1\">\n" +            "    <thead>\n" +            columnHtml +            "    </thead>\n" +            "    <tbody>\n" +            dataHtml +            "    </tbody>\n" +            "</table>\n" +            "</body>\n" +            "</html>";        //下载        downloadByBlob((fileName || "导出Excel")+".xls",excelHtml);    }

 

　　效果演示

　　导出txt文档

downloadByBlob("downloadByBlob-导出txt文档.txt","downloadByBlob\n导出txt简单测试\n");downloadByBase64("downloadByBase64-导出txt文档.txt","downloadByBase64\n导出txt简单测试\n");

  

 

 

　　导出Excel表格

exportExcel("xx业务Excel导出", {"id": "编号", "name": "名字", "age": "年龄", "time": "参加工作时间"}, [{            "id": "A001",            "name": "张三",            "age": "18",            "time": new Date().toLocaleString()        },{            "id": "A002",            "name": "李四",            "age": "20",            "time": new Date().toLocaleString()        }]);

 

 

　　导出word文档也是一样

 

 

　　后记

　　参考上我们之前的《FreeMarker模板引擎》，先画好我们想要的文档格式然后转成xml，调用我们封装好的方法，将构造好的xml内容转成文件，实现前端导出复杂格式文档！

　　如果有复杂数据，建议还是在后端操作，当然你也可以把数据返回前端在前端导出也行

 

　　前端导出Excel主要是利用Bolb、base64，以及Excel支持html格式的特性，这个特性不仅前端可以利用，后端也一样可以，这里也分享一下后端工具类，原理都是一样的

package cn.huanzi.qch.util;import javax.servlet.http.HttpServletResponse;import java.io.File;import java.io.OutputStream;import java.io.PrintWriter;import java.text.SimpleDateFormat;import java.util.*;/** * Excel工具类 */public class ExcelUtil {    /**     * 导出     * 无需依赖POI     */    /*        示例：        try {            //列名            LinkedHashMap<String, String> columns = new LinkedHashMap<>(4);            columns.put("id","编号");            columns.put("name","名字");            columns.put("age","年龄");            columns.put("time","参加工作时间");            //数据            List<Map<String, Object>> datas = new ArrayList<>(3);            HashMap<String, Object> hashMap = new HashMap<>();            hashMap.put("id","A001");            hashMap.put("name","张三");            hashMap.put("age",18);            hashMap.put("time",new Date());            datas.add(hashMap);            //带换行符：&#10;            HashMap<String, Object> hashMap2 = new HashMap<>();            hashMap2.put("id","A002");            hashMap2.put("name","李四&#10;李四1&#10;李四2");            hashMap2.put("age",20);            hashMap2.put("time",new Date());            datas.add(hashMap2);            HashMap<String, Object> hashMap3 = new HashMap<>();            hashMap3.put("id","A003");            hashMap3.put("name","王五");            hashMap3.put("age",25);            hashMap3.put("time",new Date());            datas.add(hashMap3);            //导出            ExcelUtil.exportByResponse(this.getResponse(),"Excel导出测试",columns,datas);            //ExcelUtil.exportByFile(new File("D:\\XFT User\\Downloads\\Excel导出测试.xls"),columns,datas);        } catch (Exception e) {            e.printStackTrace();        }     */    public static void exportByResponse(HttpServletResponse response, String fileName, LinkedHashMap<String, String> columns, List<Map<String, Object>> datas) throws Exception {        response.addHeader("Content-disposition", "attachment; filename=" + fileName + ".xls");        response.setContentType("application/ms-excel");        StringBuilder sb = exportOfData(columns, datas);        OutputStream out = response.getOutputStream();        out.write(sb.toString().getBytes("UTF-8"));        out.flush();        out.close();    }    public static void exportByFile(File file, LinkedHashMap<String, String> columns, List<Map<String, Object>> datas) {        StringBuilder sb = exportOfData(columns, datas);        try (PrintWriter myFile = new PrintWriter(file,"UTF-8")) {            myFile.println(sb);        } catch (Exception e) {            System.err.println("exportByFile()，操作出错...");            e.printStackTrace();        }        System.out.println(file.getName() + "，操作完成！");    }    //其他单元格无边框    private static StringBuilder exportOfData(LinkedHashMap<String, String> columns, List<Map<String, Object>> datas) {        StringBuilder sb = new StringBuilder("<html xmlns:o=\"urn:schemas-microsoft-com:office:office\"" +                "      xmlns:x=\"urn:schemas-microsoft-com:office:excel\"" +                "      xmlns=\"http://www.w3.org/TR/REC-html40\">");        //加这个，其他单元格带边框        sb.append("<head>" +                "    <xml>" +                "        <x:ExcelWorkbook>" +                "            <x:ExcelWorksheets>" +                "                <x:ExcelWorksheet>" +                "                    <x:Name></x:Name>" +                "                    <x:WorksheetOptions>" +                "                        <x:DisplayGridlines/>" +                "                    </x:WorksheetOptions>" +                "                </x:ExcelWorksheet>" +                "            </x:ExcelWorksheets>" +                "        </x:ExcelWorkbook>" +                "    </xml>" +                "   <style>td{font-family: \"宋体\";}</style>" +                "</head>");        sb.append("<body>");        sb.append("<table border=\"1\">");        //列名        sb.append("<tr style=\"text-align: center;\">");        for (Map.Entry<String, String> entry : columns.entrySet()) {            sb.append("<td style=\"background-color:#bad5fd\">" + entry.getValue() + "</td>");        }        sb.append("</tr>");        //数据        for (Map<String, Object> data : datas) {            sb.append("<tr style=\"text-align: center;\">");            for (Map.Entry<String, String> entry : columns.entrySet()) {                Object dataValue = data.get(entry.getKey());                //如果是日期类型                if (dataValue instanceof java.util.Date) {                    dataValue = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(dataValue);                }                sb.append("<td>" + dataValue.toString() + "</td>");            }            sb.append("</tr>");        }        sb.append("</table>");        sb.append("</body>");        sb.append("</html>");        return sb;    }    //前端导出Excel    /*        示例：         exportExcel("xx业务Excel导出", {"id": "编号", "name": "名字", "age": "年龄", "time": "参加工作时间"}, [{            "id": "A001",            "name": "张三",            "age": "18",            "time": new Date().toLocaleString()        },{            "id": "A002",            "name": "李四",            "age": "20",            "time": new Date().toLocaleString()        }]);     */    /*        //blob、base64转文件下载，通过A标签模拟点击,设置文件名        //万能流  application/octet-stream        //word文件  application/msword        //excel文件  application/vnd.ms-excel        //txt文件  text/plain        //图片文件  image/png、jpeg、gif、bmp        function downloadByBlob(fileName, text) {            let a = document.createElement("a");            a.href = URL.createObjectURL(new Blob([text], {type: "application/octet-stream"}));            a.download = fileName || 'Blob导出测试.txt';            a.click();            a.remove();            URL.revokeObjectURL(a.href);        }        function downloadByBase64(fileName, text) {            let a = document.createElement('a');            a.href = 'data:application/octet-stream;base64,' + window.btoa(unescape(encodeURIComponent(text)));            a.download = fileName || 'Base64导出测试.txt';            a.click();            a.remove();            URL.revokeObjectURL(a.href);        }            //踹掉后端，前端导出Excel！        function exportExcel(fileName,columns,datas){            //列名            let columnHtml = "";            columnHtml += "<tr style=\"text-align: center;\">\n";            for (let key in columns) {                columnHtml += "<td style=\"background-color:#bad5fd\">"+columns[key]+"</td>\n";            }            columnHtml += "</tr>\n";                //数据            let dataHtml = "";            for (let data of datas) {                dataHtml += "<tr style=\"text-align: center;\">\n";                for (let key in columns) {                    dataHtml += "<td>"+data[key]+"</td>\n";                }                dataHtml += "</tr>\n";            }                //完整html            let excelHtml = "<html xmlns:o=\"urn:schemas-microsoft-com:office:office\"\n" +                    "      xmlns:x=\"urn:schemas-microsoft-com:office:excel\"\n" +                    "      xmlns=\"http://www.w3.org/TR/REC-html40\">\n" +                    "<head>\n" +                    "   <!-- 加这个，其他单元格带边框 -->" +                    "   <xml>\n" +                    "        <x:ExcelWorkbook>\n" +                    "            <x:ExcelWorksheets>\n" +                    "                <x:ExcelWorksheet>\n" +                    "                    <x:Name></x:Name>\n" +                    "                    <x:WorksheetOptions>\n" +                    "                        <x:DisplayGridlines/>\n" +                    "                    </x:WorksheetOptions>\n" +                    "                </x:ExcelWorksheet>\n" +                    "            </x:ExcelWorksheets>\n" +                    "        </x:ExcelWorkbook>\n" +                    "   </xml>\n" +                    "   <style>td{font-family: \"宋体\";}</style>\n" +                    "</head>\n" +                    "<body>\n" +                    "<table border=\"1\">\n" +                    "    <thead>\n" +                    columnHtml +                    "    </thead>\n" +                    "    <tbody>\n" +                    dataHtml +                    "    </tbody>\n" +                    "</table>\n" +                    "</body>\n" +                    "</html>";                //下载            downloadByBlob((fileName || "导出Excel")+".xls",excelHtml);        }     */}

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