大家好，我是力哥。
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；
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；
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 <T> * @return */ public static <T> List<List<T>> averageAssign(List<T> source,int n){ List<List<T>> result=newArrayList<List<T>>(); int remaider=source.size()%n; int number=source.size()/n; int offset=0;//偏移量 for(int i=0;i<n;i++){ List<T> 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 { privatestaticintmaxPoolSize= Runtime.getRuntime().availableProcessors(); privatevolatilestatic ExecutorService executorService; publicstatic ExecutorService getThreadPool() { if (executorService == null){ synchronized (ExecutorConfig.class){ if (executorService == null){ executorService = newThreadPool(); } } } return executorService; } private static ExecutorService newThreadPool(){ intqueueSize=500; intcorePool= Math.min(5, maxPoolSize); returnnew ThreadPoolExecutor(corePool, maxPoolSize, 10000L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>(queueSize),newThreadPoolExecutor.AbortPolicy()); } privateExecutorConfig(){ } }/** 获取sqlSession * @version V1.0 */ @Component public class SqlContext { @Resource private SqlSessionTemplate sqlSessionTemplate; public SqlSession getSqlSession(){ SqlSessionFactorysqlSessionFactory= sqlSessionTemplate.getSqlSessionFactory(); return sqlSessionFactory.openSession(); } }示例事务不成功操作
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/** * 测试多线程事务. * @param employeeDOList */ @Override @Transactional(rollbackFor = Exception.class) public void saveThread(List<EmployeeDO> 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 ExecutorServiceservice= ExecutorConfig.getThreadPool(); //拆分数据,拆分5份 List<List<EmployeeDO>> lists=averageAssign(employeeDOList,2); //执行的线程 Thread []threadArray = newThread[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 CountDownLatchcountDownLatch=newCountDownLatch(lists.size()); AtomicBooleanatomicBoolean=newAtomicBoolean(false); for (inti=0;i<lists.size();i++){ List<EmployeeDO> list = lists.get(i); threadArray[i] = newThread(() -> { try { if (!atomicBoolean.get()){ thrownew 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 (inti=0; i <lists.size(); i++){ service.execute(threadArray[i]); } //当子线程执行完毕时,主线程再往下执行 countDownLatch.await(); System.out.println("添加完毕"); }catch (Exception e){ log.info("error",e); thrownew ServiceException("002","出现异常"); } }//测试用例 @RunWith(SpringRunner.class) @SpringBootTest(classes = { ThreadTest01.class, MainApplication.class}) public class ThreadTest01 { @Resource private EmployeeBO employeeBO; /** * 测试多线程事务. * @throws InterruptedException */ @Test public void MoreThreadTest2() throws InterruptedException { intsize=10; List<EmployeeDO> employeeDOList = new ArrayList<>(size); for (inti=0; i<size;i++){ EmployeeDOemployeeDO=newEmployeeDO(); employeeDO.setEmployeeName("lol"+i); employeeDO.setAge(18); employeeDO.setGender(1); employeeDO.setIdNumber(i+"XX"); employeeDO.setCreatTime(Calendar.getInstance().getTime()); employeeDOList.add(employeeDO); } try { employeeBO.saveThread(employeeDOList); System.out.println("添加成功"); }catch (Exception e){ e.printStackTrace(); } } }测试结果：
可以发现子线程组执行时,所有线程执行失败抛出异常,但是主线程中执行的删除操作,没有回滚,Transactional注解没有生效.
使用sqlSession控制手动提交事务
@Resource SqlContext sqlContext; /** * 测试多线程事务. * @param employeeDOList */ @Override public void saveThread(List<EmployeeDO> employeeDOList)throws SQLException { // 获取数据库连接,获取会话(内部自有事务) SqlSessionsqlSession= sqlContext.getSqlSession(); Connectionconnection= sqlSession.getConnection(); try { // 设置手动提交 connection.setAutoCommit(false); //获取mapper EmployeeMapperemployeeMapper= sqlSession.getMapper(EmployeeMapper.class); //先做删除操作 employeeMapper.delete(null); //获取执行器 ExecutorServiceservice= ExecutorConfig.getThreadPool(); List<Callable<Integer>> callableList = newArrayList<>(); //拆分list List<List<EmployeeDO>> lists=averageAssign(employeeDOList, 5); for (inti=0;i<lists.size();i++){ AtomicBooleanatomicBoolean=newAtomicBoolean(true); if (i==lists.size()-1){ atomicBoolean.set(false); } List<EmployeeDO> list = lists.get(i); //使用返回结果的callable去执行, Callable<Integer> callable = () -> { if (!atomicBoolean.get()){ thrownew ServiceException("001","出现异常"); } return employeeMapper.saveBatch(list); }; callableList.add(callable); } //执行子线程 List<Future<Integer>> futures = service.invokeAll(callableList); for (Future<Integer> 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); thrownew ServiceException("002","出现异常"); }finally { connection.close(); } }// sql <insert id="saveBatch" parameterType="List"> INSERT INTO employee(employee_id,age,employee_name,birth_date,gender,id_number,creat_time,update_time,status) values <foreach collection="list" item="item" index="index" separator=","> ( #{ item.employeeId}, #{ item.age}, #{ item.employeeName}, #{ item.birthDate}, #{ item.gender}, #{ item.idNumber}, #{ item.creatTime}, #{ item.updateTime}, #{ item.status} ) </foreach> </insert>数据库中一条数据：
篇幅限制下面就只能给大家展示小册部分内容了。整理了一份核心面试笔记包括了：Java面试、Spring、JVM、MyBatis、Redis、MySQL、并发编程、微服务、Linux、Springboot、SpringCloud、MQ、Kafc
需要全套面试笔记及答案
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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<EmployeeDO> employeeDOList)throws SQLException { // 获取数据库连接,获取会话(内部自有事务) SqlSessionsqlSession= sqlContext.getSqlSession(); Connectionconnection= sqlSession.getConnection(); try { // 设置手动提交 connection.setAutoCommit(false); EmployeeMapperemployeeMapper= sqlSession.getMapper(EmployeeMapper.class); //先做删除操作 employeeMapper.delete(null); ExecutorServiceservice= ExecutorConfig.getThreadPool(); List<Callable<Integer>> callableList = newArrayList<>(); List<List<EmployeeDO>> lists=averageAssign(employeeDOList, 5); for (inti=0;i<lists.size();i++){ List<EmployeeDO> list = lists.get(i); Callable<Integer> callable = () -> employeeMapper.saveBatch(list); callableList.add(callable); } //执行子线程 List<Future<Integer>> futures = service.invokeAll(callableList); for (Future<Integer> 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); thrownew ServiceException("002","出现异常"); // throw new ServiceException(ExceptionCodeEnum.EMPLOYEE_SAVE_OR_UPDATE_ERROR); } }数据库中数据：
删除的删除了,添加的添加成功了,测试成功.
