【Java】【47】导出数据到Excel

前言：

一般后台的报表查询页面，都会有导出数据到Excel表的功能

正文：

JS：

window.open("后台接口地址");

Controller层：

@ApiOperation(value = "导出列表")
@RequestMapping(value = "excel/exportExcel", method = RequestMethod.GET)
public void exportExcel(HttpServletResponse response, QueryVo query) {
    this.theService.exportCsvPointList(response, query);
}

Service层：

@Override
public void exportCsvPointList(HttpServletResponse response, QueryVo query) {
    String title = "积分记录";
    String fileName = title + ".csv";

    //根据查询条件query，查询出对应的数据
    List<Entity> list;

    LinkedHashMap<String, String> headMap = new LinkedHashMap<>();
    headMap.put("phone", "手机号"); //phone为Entity中的字段名，手机号为excel表的表头名称
    headMap.put("name", "姓名");

    ExportCsvUtil.exportCSV(title, fileName, list, headMap, response);
}

工具类：

ExportCsvUtil

package com.bf.base.utils;

import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map.Entry;

/**
 * 下载CSV文件
 */
public class ExportCsvUtil {
    /**
     * @param response 返回体
     * @param list 数据集合
     * @param title 主标题
     * @param map 子标题与对象属性的映射
     * @param fileName 文件名
     */

    public static <T> void exportCSV (String title, , String fileName, List<T> list, LinkedHashMap<String,String> map, HttpServletResponse response) {
        JSONArray array = new JSONArray();
        for (T obj : list) {
            array.add(obj);
        }
        
        // 表格头
        List<String> headList = new ArrayList<>();
        for (Entry<String, String> entry : map.entrySet()) {
            headList.add(entry.getValue());
        }
        
        // 数据
        BufferedWriter csvWtriter = null;
        try {
            List<List<String>> dataList = new ArrayList<List<String>>();
            for (Object obj : array) {
                List<String> rowList = new ArrayList<>();
                JSONObject jo = (JSONObject) JSONObject.toJSON(obj);
                for (Entry<String, String> entry : map.entrySet()) {
                    String value = entry.getValue();
                    String key = entry.getKey();
                    String joValue = jo.get(key) == null ? "" : jo.get(key).toString();
                    rowList.add(joValue);
                }
                dataList.add(rowList);
            }

            // 文件下载，使用如下代码
             response.setContentType("application/csv;charset=gb18030");
             response.setHeader("Content-disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
             ServletOutputStream out = response.getOutputStream();
             csvWtriter = new BufferedWriter(new OutputStreamWriter(out, "gb18030"), 1024);

            /*int num = headList.size() / 2;
            StringBuffer buffer = new StringBuffer();
            for (int i = 0; i < num; i++) {
                buffer.append(" ,");
            }
            csvWtriter.write(buffer.toString() + title + buffer.toString());
            csvWtriter.newLine();*/

            // 写入文件头部
            writeRow(headList, csvWtriter);

            // 写入文件内容
            for (List<String> row : dataList) {
                writeRow(row, csvWtriter);
            }
            csvWtriter.flush();
            csvWtriter.close();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                csvWtriter.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 写一行数据
     * @param row 数据列表
     * @param csvWriter
     * @throws IOException
     */
    private static void writeRow(List<String> row, BufferedWriter csvWriter) throws IOException {
        for (String data : row) {
            StringBuffer sb = new StringBuffer();
            String rowStr = sb.append(""").append(data).append("",").toString();
            csvWriter.write(rowStr);
        }
        csvWriter.newLine();
    }
}