1.首先從網上找一個到工具類，我這里是ExcelUtils，如下
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package com.org.util;import org.apache.poi.xssf.streaming.SXSSFCell;
import org.apache.poi.xssf.streaming.SXSSFRow;
import org.apache.poi.xssf.streaming.SXSSFSheet;import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;public class ExcelUtils {// 導出 Excelpublic static Integer exportExcel(SXSSFSheet sheet, List<Object> dataList, Integer currentRow) throws IntrospectionException, InvocationTargetException, IllegalAccessException {if (null == dataList || dataList.size() == 0) {return -1;}// 反射Object object = dataList.get(0);Class<?> clazz = object.getClass();Field[] fields = clazz.getDeclaredFields();//如果是第一行，創建表頭if (0 == currentRow) {SXSSFRow row = sheet.createRow(currentRow++);for (int i = 0; i < fields.length; i++) {SXSSFCell cell = row.createCell(i);cell.setCellValue(fields[i].getName());//設置單元格的值為字段名}}//填充數據for (Object item : dataList) {SXSSFRow row = sheet.createRow(currentRow++);for (int i = 0; i < fields.length; i++) {SXSSFCell cell = row.createCell(i);// get MethodPropertyDescriptor propertyDescriptor = new PropertyDescriptor(fields[i].getName(), item.getClass());Method getMethod = propertyDescriptor.getReadMethod();// valueObject value = getMethod.invoke(item);cell.setCellValue(value.toString());//設置單元格的值為字段值的字符表現形式}}return currentRow;}
}public class DataBaseTest {private static final ConcurrentHashMap<Integer, FutureTask<Integer>> taskList = new ConcurrentHashMap<>();public static void main(String[] args) throws ExecutionException, InterruptedException, IOException {// mapperSqlSession sqlSession = MyBatisUtils.getSqlSession();UserMapper userMapper = sqlSession.getMapper(UserMapper.class);// 查出總數int totalNum = userMapper.getTotalNum();// 10個線程數int taskNum = 10;// 總數據量int avg = (int) Math.floor(totalNum / taskNum);int[] startRows = calcStartRowIndex(totalNum, taskNum);// ExcelSXSSFWorkbook workbook = new SXSSFWorkbook();SXSSFSheet sheet = workbook.createSheet();for (int i = 0; i < taskNum; i++) {final int temp = i;FutureTask<Integer> futureTask = new FutureTask<>(new Callable<Integer>() {@Overridepublic Integer call() throws Exception {System.out.println("開始執行任務" + temp + "...");HashMap<String, Object> map = new HashMap<>();List<User> userList = null;// 分頁查詢if (temp == taskNum - 1) {// 如果是最后一個線程map.put("startIndex", startRows[temp] - 1); //9001-1// 計算起始位置到最后的數量map.put("num", totalNum - startRows[temp] + 1); //10001-9001+1userList = userMapper.getListByPage(map);} else {//如果是前九個線程的花執行下面的操作map.put("startIndex", startRows[temp] == 0 ? 0 : startRows[temp] - 1);map.put("num", avg);userList = userMapper.getListByPage(map);}List<Object> dataList = new ArrayList<>();for (User user : userList) {dataList.add(user);}Integer currentRow = ExcelUtils.exportExcel(sheet, dataList, startRows[temp]);System.out.println("任務" + temp + "執行結束...");return currentRow;}});taskList.putIfAbsent(i, futureTask);}int taskIndex = 0;while (true) {FutureTask<Integer> futureTask = taskList.remove(taskIndex++);if (null != futureTask) {futureTask.run();Integer currentRow = futureTask.get();}if (taskList.size() == 0) {// 寫入磁盤System.out.println("開始寫入磁盤");FileOutputStream fileOutputStream = new FileOutputStream(new File("c:\\users\\che\\desktop\\test01.xlsx"));workbook.write(fileOutputStream);break;}}}// 計算每一趟起始位置public static int[] calcStartRowIndex(int totalNum, int taskNum) {int[] resultArray = new int[taskNum];int avg = (int) Math.floor(totalNum / taskNum);for (int i = 0; i < taskNum; i++) {if (i == 0) {resultArray[i] = i * avg;} else {resultArray[i] = i * avg + 1;}}return resultArray;}public static void addDataSource() {SqlSession sqlSession = MyBatisUtils.getSqlSession();try {UserMapper userMapper = sqlSession.getMapper(UserMapper.class);for (int i = 0; i < 10000; i++) {User user = new User("T" + i, i, "男", "10086", "qwe@qq.com", "日本京都");System.out.println(user);userMapper.addUser(user);}sqlSession.commit();} catch (Exception e) {e.printStackTrace();} finally {
// sqlSession.close();}}
}具體代碼示例包在次處
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