多线程事务怎么回滚？说用Transactional可以回去等通知了！

　　背景介绍
　　1，最近有一个大数据量插入的操作入库的业务场景，需要先做一些其他修改操作，然后在执行插入操作，由于插入数据可能会很多，用到多线程去拆分数据并行处理来提高响应时间，如果有一个线程执行失败，则全部回滚。
　　2，在spring中可以使用 @Transactional 注解去控制事务，使出现异常时会进行回滚，在多线程中，这个注解则不会生效，如果主线程需要先执行一些修改数据库的操作，当子线程在进行处理出现异常时，主线程修改的数据则不会回滚，导致数据错误。
　　3，下面用一个简单示例演示多线程事务。 公用的类和方法/**  * 平均拆分list方法.  * @param source  * @param n  * @param   * @return  */ public static  List> averageAssign(List source,int n){     List> result=new ArrayList>();     int remaider=source.size()%n;     int number=source.size()/n;     int offset=0;//偏移量     for(int i=0;i value=null;         if(remaider>0){             value=source.subList(i*number+offset, (i+1)*number+offset+1);             remaider--;             offset++;         }else{             value=source.subList(i*number+offset, (i+1)*number+offset);         }         result.add(value);     }     return result; } /**  线程池配置  * @version V1.0  */ public class ExecutorConfig {     private static int maxPoolSize = Runtime.getRuntime().availableProcessors();     private volatile static ExecutorService executorService;     public static ExecutorService getThreadPool() {         if (executorService == null){             synchronized (ExecutorConfig.class){                 if (executorService == null){                     executorService =  newThreadPool();                 }             }         }         return executorService;     }      private static  ExecutorService newThreadPool(){         int queueSize = 500;         int corePool = Math.min(5, maxPoolSize);         return new ThreadPoolExecutor(corePool, maxPoolSize, 10000L, TimeUnit.MILLISECONDS,             new LinkedBlockingQueue<>(queueSize),new ThreadPoolExecutor.AbortPolicy());     }     private ExecutorConfig(){} } /** 获取sqlSession  * @author 86182  * @version V1.0  */ @Component public class SqlContext {     @Resource     private SqlSessionTemplate sqlSessionTemplate;      public SqlSession getSqlSession(){         SqlSessionFactory sqlSessionFactory = sqlSessionTemplate.getSqlSessionFactory();         return sqlSessionFactory.openSession();     } }示例事务不成功操作  /**  * 测试多线程事务.  * @param employeeDOList  */ @Override @Transactional public void saveThread(List employeeDOList) {     try {         //先做删除操作,如果子线程出现异常,此操作不会回滚         this.getBaseMapper().delete(null);         //获取线程池         ExecutorService service = ExecutorConfig.getThreadPool();         //拆分数据,拆分5份         List> lists=averageAssign(employeeDOList, 5);         //执行的线程         Thread []threadArray = new Thread[lists.size()];         //监控子线程执行完毕,再执行主线程,要不然会导致主线程关闭,子线程也会随着关闭         CountDownLatch countDownLatch = new CountDownLatch(lists.size());         AtomicBoolean atomicBoolean = new AtomicBoolean(true);         for (int i =0;i list  = lists.get(i);             threadArray[i] =  new Thread(() -> {                 try {                  //最后一个线程抛出异常                     if (!atomicBoolean.get()){                         throw new ServiceException(＂001＂,＂出现异常＂);                     }                     //批量添加,mybatisPlus中自带的batch方法                     this.saveBatch(list);                 }finally {                     countDownLatch.countDown();                 }              });         }         for (int i = 0; i  employeeDOList = new ArrayList<>(size);         for (int i = 0; i employeeDOList) throws SQLException {     // 获取数据库连接,获取会话(内部自有事务)     SqlSession sqlSession = sqlContext.getSqlSession();     Connection connection = sqlSession.getConnection();     try {         // 设置手动提交         connection.setAutoCommit(false);         //获取mapper         EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);         //先做删除操作         employeeMapper.delete(null);         //获取执行器         ExecutorService service = ExecutorConfig.getThreadPool();         List> callableList  = new ArrayList<>();         //拆分list         List> lists=averageAssign(employeeDOList, 5);         AtomicBoolean atomicBoolean = new AtomicBoolean(true);         for (int i =0;i list  = lists.get(i);             //使用返回结果的callable去执行,             Callable callable = () -> {                 //让最后一个线程抛出异常                 if (!atomicBoolean.get()){                     throw new ServiceException(＂001＂,＂出现异常＂);                 }               return employeeMapper.saveBatch(list);             };             callableList.add(callable);         }         //执行子线程        List> futures = service.invokeAll(callableList);         for (Future future:futures) {         //如果有一个执行不成功,则全部回滚             if (future.get()<=0){                 connection.rollback();                  return;             }         }         connection.commit();         System.out.println(＂添加完毕＂);     }catch (Exception e){         connection.rollback();         log.info(＂error＂,e);         throw new ServiceException(＂002＂,＂出现异常＂);     }finally {          connection.close();      } } // sql   INSERT INTO  employee (employee_id,age,employee_name,birth_date,gender,id_number,creat_time,update_time,status)  values            (      #{item.employeeId},      #{item.age},      #{item.employeeName},      #{item.birthDate},      #{item.gender},      #{item.idNumber},      #{item.creatTime},      #{item.updateTime},      #{item.status}          )        
　　数据库中一条数据：
　　测试结果：抛出异常，
　　删除操作的数据回滚了，数据库中的数据依旧存在，说明事务成功了。
　　成功操作示例：  @Resource SqlContext sqlContext; /**  * 测试多线程事务.  * @param employeeDOList  */ @Override public void saveThread(List employeeDOList) throws SQLException {     // 获取数据库连接,获取会话(内部自有事务)     SqlSession sqlSession = sqlContext.getSqlSession();     Connection connection = sqlSession.getConnection();     try {         // 设置手动提交         connection.setAutoCommit(false);         EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);         //先做删除操作         employeeMapper.delete(null);         ExecutorService service = ExecutorConfig.getThreadPool();         List> callableList  = new ArrayList<>();         List> lists=averageAssign(employeeDOList, 5);         for (int i =0;i list  = lists.get(i);             Callable callable = () -> employeeMapper.saveBatch(list);             callableList.add(callable);         }         //执行子线程        List> futures = service.invokeAll(callableList);         for (Future future:futures) {             if (future.get()<=0){                 connection.rollback();                  return;             }         }         connection.commit();         System.out.println(＂添加完毕＂);     }catch (Exception e){         connection.rollback();         log.info(＂error＂,e);         throw new ServiceException(＂002＂,＂出现异常＂);        // throw new ServiceException(ExceptionCodeEnum.EMPLOYEE_SAVE_OR_UPDATE_ERROR);     } }
　　测试结果：
　　数据库中数据：
　　删除的删除了，添加的添加成功了，测试成功。