java excel导出

package com.ruoyi.primary.utils;

import cn.hutool.core.collection.CollUtil;

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.lang.reflect.Field;
import java.math.BigDecimal;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.*;

import javax.servlet.ServletOutputStream;
import javax.servlet.ServletResponse;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletResponse;

public class ExportTools{

    private StringBuffer content = new StringBuffer();

    /**
     * 导出excel(利用反射机制)
     * <br>
     * String[] title = {"订单号","商品名称","商品价格","创建时间"};<br>
     * String[] field = {"orderNum","productName","productPrice","createTime"};<br>
     * ExportTools.export("sellJoin", title, field, list, respone);<br>
     * <br>
     * 支持字段规则转换
     * <br>
     * 后追加 buyNum[&个]
     * <br>
     * 除法 investMoney[/100]
     * <br>
     * 乘法 investMoney[*100]
     * <br>
     * 类型转换 capitalType[1_金豆,2_钱包,3_其他]
     * <br>
     * @param filename 导出文件名称
     * @param title 列标题
     * @param field 要导出的对象属性字段，（与列标题要 一一对应）
     * @param pesponse
     */
    public static void export(String filename, String[] title,String[] field,List<? extends Object> list,
                              HttpServletResponse pesponse){
        new ExportTools().exportExcel(filename, title, field, list, pesponse);
    }

    /**
     * 导出excel(利用反射机制)例：
     * <br>
     * String[] title = {"订单号","商品名称","商品价格","创建时间"};<br>
     * String[] field = {"orderNum","productName","productPrice","createTime"};<br>
     * ExportTools.export("sellJoin", title, field, list, respone);<br>
     * <br>
     * 支持字段规则转换
     * <br>
     * 后追加 buyNum[&个]
     * <br>
     * 除法 investMoney[/100]
     * <br>
     * 乘法 investMoney[*100]
     * <br>
     * 类型转换 capitalType[1_金豆,2_钱包,3_其他]
     * <br>
     * @param filename 导出文件名称
     * @param title 列标题
     * @param field 要导出的对象属性字段，（与列标题要 一一对应）
     * @param list 导出数据list集合
     * @param pesponse
     */
    public void exportExcel(String filename, String[] title,String[] field,List<? extends Object> list,
                            HttpServletResponse pesponse){
        setTitle(title);
        try{
            for (int i = 0; i < list.size(); i++) {
                for (int j = 0; j < field.length; j++) {
                    Object t = list.get(i);
                    Field[] fields = t.getClass().getDeclaredFields();
                    for ( Field fd : fields ){
                        fd.setAccessible( true );
                        String fieldStr = field[j];
                        String fieldName = "";
                        //转换规则
                        Integer typeCode = 0;
                        Map<Integer, String> ruleMap = new HashMap<Integer, String>();//类型转换规则
                        if(fieldStr.indexOf("[") > 1){
                            fieldName = fieldStr.substring(0, fieldStr.indexOf("["));
                            String splits = fieldStr.substring(fieldStr.indexOf("[")+1,fieldStr.indexOf("]"));
                            if(splits.indexOf(",") > -1){//替换
                                typeCode = 1;
                                String[] split = splits.split(",");
                                for(String s : split){
                                    String[] types = s.split("_");
                                    ruleMap.put(Integer.parseInt(types[0]), types[1]);
                                }
                            }else if(splits.indexOf("&") > -1){//连接
                                typeCode = 2;
                                ruleMap.put(1, splits.substring(splits.indexOf("&")+1,splits.length()));
                            }else if(splits.indexOf("/") > -1){//除法
                                typeCode = 3;
                                ruleMap.put(1, splits.substring(splits.indexOf("/")+1,splits.length()));
                            }else if(splits.indexOf("*") > -1){//乘法
                                typeCode = 4;
                                ruleMap.put(1, splits.substring(splits.indexOf("*")+1,splits.length()));
                            }
                        }else{
                            fieldName = fieldStr;
                        };

                        //取值
                        if(fieldName.equals(fd.getName())){
                            Object value = new Object();
                            if("java.util.Date".equals(fd.getType().getName())){
                                value = formatDate(fd.get(t));
                            }else if("java.math.BigDecimal".equals(fd.getType().getName())){
                                value = fd.get(t);
                            }else{
                                value = fd.get(t);
                            }
                            //需要做转换
                            if(typeCode != 0){
                                switch (typeCode) {
                                    case 1:
                                        value = ruleMap.get(value);
                                        break;
                                    case 2:
                                        value = value + ruleMap.get(1);
                                        break;
                                    case 3:
                                        if(null == value || "".equals(value.toString())) value = 0;
                                        value = new BigDecimal(value.toString()).divide(new BigDecimal(ruleMap.get(1)),2,BigDecimal.ROUND_HALF_UP);
                                        break;
                                    case 4:
                                        if(null == value || "".equals(value.toString())) value = 0;
                                        value = new BigDecimal(value.toString()).multiply(new BigDecimal(ruleMap.get(1)));
                                        break;
                                    default:
                                        break;
                                }
                            }
                            setField(value);
                            break;
                        }
                    }
                }
                content.append("\n");
            }
            downloadFileCsv(getFileName(filename), content.toString(), pesponse);
        }catch ( Exception e ){
            System.err.println("导出文件:"+filename+" 出错");
            e.printStackTrace();
        }
    }

    /**
     * 生成excel
     * @param filename
     * @param content
     * @param response
     * @throws IOException
     */
    public void downloadFileCsv(String filename, String content, HttpServletResponse response) throws IOException {
        response.addHeader("Content-Disposition", "attachment; filename=\"" + new String(filename.getBytes(), "UTF-8") + "\"");
        OutputStreamWriter ow = new OutputStreamWriter(response.getOutputStream(), "UTF-16LE");
        ow.write(0xFEFF);
        ow.write(content);
        if (null != ow) {
            ow.flush();
            ow.close();
        }
    }

    /**
     * 设置标题
     * @param title
     */
    private void setTitle(String[] title){
        for (int i = 0; i < title.length; i++) {
            content.append((title[i] == null || "null".equals(title[i].toString())
                    ? "" : title[i].toString()) + "\t");
        }
        content.append("\n");
    }

    /**
     * 设置列表数据
     * @param value
     */
    private void setField(Object value){
        content.append((value == null || "null".equals(value.toString())
                ? "" : value.toString()) + "\t");
    }

    /**
     * 生成当前时间的后缀文件名
     * @param fileName
     * @return
     */
    private String getFileName(String fileName){
        SimpleDateFormat dateFormat = new SimpleDateFormat("MMddHHmm");
        return fileName + dateFormat.format(new Date()) +".csv";
    }

    /**
     * 时间类型转化
     * @return
     * Date:2017年10月25日上午11:53:10
     */
    private String formatDate(Object obj){
        if(obj == null){
            return "";
        }
        DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return format.format((Date)obj);
    }
}