public class POITest2 {public static void main(String[] args) throws Exception{String xlsFile = "c:/poiSXSSFDBBigData.xlsx";        //输出文件Workbook wb = new SXSSFWorkbook();                //创建excel文件，内存只有100条记录【关键语句】Sheet sheet = wb.createSheet("我的第一个工作簿");        //建立新的sheet对象Row nRow = null;Cell nCell   = null;//使用jdbc链接数据库Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();      String url = "jdbc:oracle:thin:@127.0.0.1:1521:ORCL";String user = "itheima";String password = "itheima";Connection conn = DriverManager.getConnection(url, user,password);   Statement stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);   String sql = "SELECT * FROM CONTRACT_PRODUCT_C";       //100万测试数据ResultSet rs = stmt.executeQuery(sql);                          //bug 要分次读取，否则记录过多long  startTime = System.currentTimeMillis();    //开始时间System.out.println("strat execute time: " + startTime);//contextint rowNo = 0;int colNo = 0;while(rs.next()) {for(int i=0;i<5000;i++){colNo = 0;nRow = sheet.createRow(rowNo++);nCell = nRow.createCell(colNo++);nCell.setCellValue(rs.getString(colNo));nCell = nRow.createCell(colNo++);nCell.setCellValue(rs.getString(colNo));if(rowNo%100==0){System.out.println("row no: " + rowNo);}}Thread.sleep(1);            //休息一下，防止对CPU占用}long finishedTime = System.currentTimeMillis();    //处理完成时间System.out.println("finished execute  time: " + (finishedTime - startTime)/1000 + "s");FileOutputStream fOut = new FileOutputStream(xlsFile);wb.write(fOut);fOut.flush();fOut.close();long stopTime = System.currentTimeMillis();        //写文件时间System.out.println("write xlsx file time: " + (stopTime - startTime)/1000 + "s");close(rs, stmt, conn);}//close resourceprivate static  void close(ResultSet rs, Statement stmt, Connection conn ) throws SQLException{rs.close();   stmt.close();   conn.close();}    }