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利用java如何实现把对象数组导出从Excel文件

利用java如何实现把对象数组导出从Excel文件？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。

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一、导入相关jar包，pom依赖如下：

  
   org.apache.poi
   poi
   RELEASE

二、开始撸代码

1.如果导出功能使用的比较多，可以将其做成一个工具类，对我下面贴出的代码进行改造

//结果返回的是写入的记录数（以下用的是自己业务场景数据）
　　public int downLoadToExcel(OutputStream outputStream,List paimaiMoneyVOList) {
　　　　　//文档对象
  HSSFWorkbook wb = new HSSFWorkbook();
  int rowNum = 0;
  Sheet sheet = wb.createSheet("excel的标题");
  Row row0 = sheet.createRow(rowNum++);
　　　　//因为场景不同，titil不同，可以在外面写成数组当参数传进来
  row0.createCell(0).setCellValue("第一列属性名");
  row0.createCell(1).setCellValue("第二列属性名");
  row0.createCell(2).setCellValue("第三列属性名");
  row0.createCell(3).setCellValue("第四列属性名");
  row0.createCell(4).setCellValue("第五列属性名");
  row0.createCell(5).setCellValue("第六列属性名");
　　　　 if (paimaiMoneyVOList != null && paimaiMoneyVOList.size() > 0) {
   for (PaimaiMoneyVO paimaiMoneyVO : paimaiMoneyVOList) {
    Row row = sheet.createRow(rowNum++);
    row.createCell(0).setCellValue(paimaiMoneyVO.getPaimaiId());
    row.createCell(1).setCellValue(paimaiMoneyVO.getTitle());
    row.createCell(2).setCellValue(paimaiMoneyVO.getUsername());
    row.createCell(3).setCellValue(paimaiMoneyVO.getMoney()+"元");
    row.createCell(4).setCellValue("升价拍"); 
    row.createCell(5).setCellValue(bidder);
   }
  }
  try {
   wb.write(outputStream);
   LogEnum.LAW_WARE.info("表数据写入到excel表成功,一共写入了"+(rowNum - 1)+"条数据");
   outputStream.close();
  } catch (IOException e) {
   LogEnum.LAW_WARE.error("流关闭异常！", e);
  } finally {
   if (outputStream != null) {
    try {
     outputStream.close();
    } catch (IOException e) {
     LogEnum.LAW_WARE.error("流关闭异常！", e);
    }
   }
  }
  return rowNum - 1;
 }

2.“工具类”写好后，下面就开始使用它了，从上面的函数参数可以看到，我们需要传过去两个对象，一个是输出流OutPutStream，通过流的方式把excel想要到浏览器，

另外一个就是我们需要导出的对象数组，好了，不解释太多，看代码。（下面的方法写在action层，通过struts.xml配置访问即可实现下载）

public void exportBail(){
  this.fileName = "excel文件名";
  try {
   List paimaiMoneyVOList = new ArrayList<>();
　　　　　　//下面是我的业务场景获取对象数组
   if(paimaiMoneySearchParam!=null){
    paimaiMoneySearchParam.setVendorId(WebHelper.getVenderId());
    paimaiMoneySearchParam.setPageSize(Constants.AUCTION_WARE_PAGE_SIZE);
    paimaiMoneySearchParam.setPage(page);
    PaimaiMoneyDto paimaiMoneyDto = auctionWareService1.searchPopPaimaiMoneyList(paimaiMoneySearchParam);
    if(paimaiMoneyDto!=null){
     int count = paimaiMoneyDto.getCount();
     int totalPage = count/ Constants.AUCTION_WARE_PAGE_SIZE + (count% Constants.AUCTION_WARE_PAGE_SIZE > 0?1:0);
     for(int i=1;i<=totalPage;i++){
      paimaiMoneySearchParam.setPage(i);
      PaimaiMoneyDto paimaiMoneyResultResult = auctionWareService1.searchPopPaimaiMoneyList(paimaiMoneySearchParam);
      if(paimaiMoneyResultResult!=null){
       paimaiMoneyVOList.addAll(paimaiMoneyResultResult.getList());
      }
     }
    }
   }
   OutputStream outputStream = response.getOutputStream();
   response.reset();//清空输出流
   //下面是对中文文件名的处理
   response.setCharacterEncoding("UTF-8");//设置相应内容的编码格式
　　　　　　　//解析浏览器
   final String userAgent = request.getHeader("USER-AGENT").toLowerCase();
   if(userAgent.contains("firefox")){ //火狐浏览器
    fileName = new String(fileName.getBytes(), "ISO8859-1");
   }else{
    fileName = URLEncoder.encode(fileName, "UTF-8"); //其他浏览器
　　　　　　　　　 fileName = fileName.Replace("+", "%20"); //encode后替换，解决空格问题（其中%20是空格在UTF-8下的编码 ，如果不这么写，浏览器会用+代替空格）
   }
   response.setHeader("Content-Disposition", "attachment;filename=" +fileName + ".xls");//指定输出文件名
   response.setContentType("application/msexcel");//定义输出类型
   int rouNum = ensurePriceListToExcel(outputStream,paimaiMoneyVOList);
   LogEnum.LAW_WARE.info("【RiseAuctionAction.downLoadEnsurePriceExcel】导出成功,一共更新了{"+rouNum+"}条记录");
  } catch (Exception e) {
   LogEnum.LAW_WARE.error("【RiseAuctionAction.downLoadEnsurePriceExcel】导出失败,error is {}", e);
  }
 }

三、拓展（详细的工具类开发）

如果你觉得上面写的太简单了，可以继续往下看，我把它整理出了“万能”的工具类，供大家参考。

package com.jd.pop.auction.util.excel;
import com.jd.common.web.result.Result;
import com.jd.pop.auction.util.excel.annotations.ExcelColumn;
import com.jd.pop.auction.util.excel.annotations.ExcelMapping;
import com.jd.pop.auction.util.excel.annotations.apt.ExcelColumnAPT;
import com.jd.pop.auction.util.excel.annotations.apt.ExcelMappingAPT;
import org.apache.log4j.Logger;
import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.hssf.util.HSSFColor;
import org.apache.poi.ss.util.CellRangeAddress;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
public class GenerateExcel {
 private final static Logger LOG = Logger.getLogger(GenerateExcel.class);
 private HSSFWorkbook workbook;
 private HSSFCellStyle headStyle;
 private HSSFFont headCellFont;
 private HSSFCellStyle theadStyle;
 private HSSFFont theadCellFont;
 private HSSFCellStyle tbodyStyle;
 private HSSFFont tbodyCellFont;
 private HSSFFont stringFont;
 private static final short COLUMN_WIDTH = 15;
 private static final short ROW_HEIGHT = 400;
 public GenerateExcel() {
  this.workbook = new HSSFWorkbook();
  //标题
  this.headStyle = workbook.createCellStyle();
  headStyle.setFillForegroundColor(HSSFColor.GREY_50_PERCENT.index);
  headStyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
//  headStyle.setBorderBottom(HSSFCellStyle.BORDER_THIN);
//  headStyle.setBorderLeft(HSSFCellStyle.BORDER_THIN);
//  headStyle.setBorderRight(HSSFCellStyle.BORDER_THIN);
//  headStyle.setBorderTop(HSSFCellStyle.BORDER_THIN);
  headStyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);

//  headStyle.setWrapText(true);
  this.headCellFont = workbook.createFont();
  headCellFont.setFontHeightInPoints((short)13);
  headCellFont.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);
  headStyle.setFont(headCellFont);
  this.theadStyle = workbook.createCellStyle();
  theadStyle.setFillForegroundColor(HSSFColor.WHITE.index);
  theadStyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
  theadStyle.setBorderBottom(HSSFCellStyle.BORDER_THIN);
  theadStyle.setBorderLeft(HSSFCellStyle.BORDER_THIN);
  theadStyle.setBorderRight(HSSFCellStyle.BORDER_THIN);
  theadStyle.setBorderTop(HSSFCellStyle.BORDER_THIN);
  theadStyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);
  theadCellFont = workbook.createFont();
  theadCellFont.setColor(HSSFColor.BLACK.index);
  theadCellFont.setFontHeightInPoints((short) 12);
  theadCellFont.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);
  theadStyle.setFont(theadCellFont);
  tbodyStyle = workbook.createCellStyle();
  tbodyStyle.setFillForegroundColor(HSSFColor.WHITE.index);
  tbodyStyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
  tbodyStyle.setBorderBottom(HSSFCellStyle.BORDER_THIN);
  tbodyStyle.setBorderLeft(HSSFCellStyle.BORDER_THIN);
  tbodyStyle.setBorderRight(HSSFCellStyle.BORDER_THIN);
  tbodyStyle.setBorderTop(HSSFCellStyle.BORDER_THIN);
  tbodyStyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);
  tbodyStyle.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
  tbodyCellFont = workbook.createFont();
  tbodyCellFont.setBoldweight(HSSFFont.BOLDWEIGHT_NORMAL);
  tbodyStyle.setFont(tbodyCellFont);
  stringFont = workbook.createFont();
  stringFont.setColor(HSSFColor.BLACK.index);
 }
 public  Result export(List titles, Field[] fields, Class clazz, Collection dataset, OutputStream out, boolean pager) {
  Result result = new Result(false);
  if(pager){
  }else{
   HSSFSheet sheet = workbook.createSheet( "第一页");
   sheet.setDefaultColumnWidth(COLUMN_WIDTH);
   sheet.setDefaultRowHeight(ROW_HEIGHT);
   //标题
   for (int i = 0; i  it = dataset.iterator();
   int index = titles.size();
   while (it.hasNext()) {
    index++;
    row = sheet.createRow(index);
    T t = (T) it.next();
    for (short i = 0; i < fields.length; i++) {
     HSSFCell cell = row.createCell(i);
     cell.setCellStyle(tbodyStyle);
     Field field = fields[i];
     try {
      String textValue;
      if(field.isAnnotationPresent(ExcelMapping.class)){
       textValue = new ExcelMappingAPT().getColumnValue(field,t,clazz);
      }else{
       textValue = new ExcelColumnAPT().getColumnValue(field,t,clazz);
      }
      cell.setCellValue(textValue);
     } catch (NoSuchMethodException e) {
      String errorMsg = field.getName() +"字段，第"+ index+ "条数据， NoSuchMethodException 反射错误！";
      LOG.error(errorMsg,e);
      result.addDefaultModel(errorMsg);
      return result;
     } catch (IllegalAccessException e) {
      String errorMsg = field.getName() +"字段，第"+ index+ "条数据， IllegalAccessException ";
      LOG.error(errorMsg,e);
      result.addDefaultModel(errorMsg);
      return result;
     } catch (InvocationTargetException e) {
      String errorMsg = field.getName() +"字段，第"+ index+ "条数据， InvocationTargetException ";
      LOG.error(errorMsg,e);
      result.addDefaultModel(errorMsg);
      return result;
     }
    }
   }
  }
  try {
   workbook.write(out);
   result.setSuccess(true);
   return result;
  } catch (IOException e) {
   String errorMsg = "将导出数据写入输出流失败!";
   LOG.error("将导出数据写入输出流失败！ ",e);
   result.addDefaultModel(errorMsg);
   return result;
  }finally {
   try {
    out.close();
   } catch (IOException e) {
    String errorMsg = "关闭输出流异常!";
    LOG.error("关闭输出流异常！ ",e);
    result.addDefaultModel(errorMsg);
    return result;
   }
  }
 }
}
public class ExportExcelUtils {
 private final static Logger LOG = Logger.getLogger(ExportExcelUtils.class);
 public static  Result export(List titles,List sourceList, OutputStream out, boolean pager){
  Result result = new Result(false);
  if(CollectionUtils.isEmpty(sourceList)){
   result.addDefaultModel("ExportExcelUtils's param sourceList is empty!");
   LOG.error("ExportExcelUtils's param sourceList is empty!");
   return result;
  }
  if( out == null){
   LOG.error("ExportExcelUtils's param OutputStream is null!");
   result.addDefaultModel("ExportExcelUtils's param OutputStream is null!");
   return result;
  }
  Class clazz = null;
  Field[] fieldArr = null;
  try{
   //得到需要转换的列名
   clazz = sourceList.get(0).getClass();
   Field[] fields = clazz.getDeclaredFields();
   List fieldList = new ArrayList();
   for(Field field:Arrays.asList(fields)){
    field.setAccessible(true);
    if(field.isAnnotationPresent(ExcelColumn.class)){
     fieldList.add(field);
    }else if(field.isAnnotationPresent(ExcelMapping.class)){
     fieldList.add(field);
    }
   }
   if(CollectionUtils.isEmpty(fieldList)){
    LOG.error("实体类中无需要导出的字段!");
    result.addDefaultModel("实体类中无需要导出的字段！");
    return result;
   }
   fieldArr = fieldList.toArray(new Field[fieldList.size()]);
  }catch(Exception e){
   LOG.error("数据拼装异常!");
   result.addDefaultModel("数据拼装异常!");
   return result;
  }
  //生成excel
  GenerateExcel ge = new GenerateExcel();
  return ge.export(titles,fieldArr,clazz,sourceList,out,false);
 }

}

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