java中使用poi导出Excel大批量数据到客户端
在java web系统应用中我们经常会用到大批量数据的导出，动辄就上几十万几百万的数据让我们的程序感觉压力很大，甚至都出现无法导出的情况，如内存溢出等。
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在这里给大家提供一种思路：分多个文件导出，在生成文件的过程中注意回收内存，
System.out.println("---------------------");File directory=null;String zipPath=null;String taskId = datas[0];String diffFlag = datas[1];try {directory = new File(String.valueOf(System.currentTimeMillis()));directory.mkdir();String directoryPath = directory.getAbsolutePath();StringBuffer buffer = new StringBuffer("select t.id,t.phone,t.diff_flag from ");buffer.append(" dcs_task_user_diff_" + taskId + " t where t.diff_flag='" + diffFlag + "' and rownum <=1000000");Connection connection = GetDBConnection.getConnection();Statement createStatement = null;createStatement = connection.createStatement();ResultSet resultSet = createStatement.executeQuery(buffer.toString());int p=0; int i=0; int j=0; HSSFWorkbook workbook=null; File file=null; HSSFSheet createSheet=null; FileOutputStream fileOutputStream=null; int countPerFile = 50000;int countPerSheet =5000;while (resultSet.next()) {if(i%countPerFile==0){int countfile=(i/countPerFile+1);String fileName=directoryPath+File.separator+countfile+".xls";System.out.println("创建第"+fileName);workbook=new HSSFWorkbook();file=new File(fileName);j=0;}if(j%countPerSheet==0){int sheetCount=(j/countPerSheet+1);System.out.println(" 创建第"+sheetCount+"个sheet");createSheet=workbook.createSheet(sheetCount+"sheet");System.gc();p=0;HSSFRow createRow = createSheet.createRow(p);createRow.createCell(0).setCellValue(new HSSFRichTextString("编号"));createRow.createCell(1).setCellValue(new HSSFRichTextString("手机号"));p++;}HSSFRow createRow = createSheet.createRow(p);createRow.createCell(0).setCellValue(new HSSFRichTextString(resultSet.getString("id")));createRow.createCell(1).setCellValue(new HSSFRichTextString(resultSet.getString("phone")));i=i+1;j=j+1;p++;if(j%countPerSheet==0||j==1){fileOutputStream = new FileOutputStream(file);workbook.write(fileOutputStream);fileOutputStream.flush();}if(j%countPerFile==0){workbook.write(fileOutputStream);fileOutputStream.flush();fileOutputStream.close();}}if(fileOutputStream!=null){fileOutputStream = new FileOutputStream(file);workbook.write(fileOutputStream);fileOutputStream.flush();}GetDBConnection.destroyConnection(connection, createStatement);System.out.println(file.getAbsolutePath());} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();} zipPath= JasperExportHelper.CreateZipFile(directory.getAbsolutePath(), directory.getAbsolutePath()+".zip");System.out.println(zipPath);return zipPath;?