背景介紹

1，最近有一個大數據量插入的操作入庫的業務場景，需要先做一些其他修改操作，然后在執行插入操作，由于插入數據可能會很多，用到多線程去拆分數據并行處理來提高響應時間，如果有一個線程執行失敗，則全部回滾。

2，在spring中可以使用@Transactional注解去控制事務，使出現異常時會進行回滾，在多線程中，這個注解則不會生效，如果主線程需要先執行一些修改數據庫的操作，當子線程在進行處理出現異常時，主線程修改的數據則不會回滾，導致數據錯誤。

3，下面用一個簡單示例演示多線程事務。

公用的類和方法

/**
?*?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;
}
/**??線程池配置
?*?@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(){}
}
/**?獲取sqlSession
?*?@author?86182
?*?@version?V1.0
?*/
@Component
public?class?SqlContext?{
????@Resource
????private?SqlSessionTemplate?sqlSessionTemplate;

????public?SqlSession?getSqlSession(){
????????SqlSessionFactory?sqlSessionFactory?=?sqlSessionTemplate.getSqlSessionFactory();
????????return?sqlSessionFactory.openSession();
????}
}

示例事務不成功操作

??/**
?*?測試多線程事務.
?*?@param?employeeDOList
?*/
@Override
@Transactional
public?void?saveThread(List?employeeDOList)?{
????try?{
????????//先做刪除操作,如果子線程出現異常,此操作不會回滾
????????this.getBaseMapper().delete(null);
????????//獲取線程池
????????ExecutorService?service?=?ExecutorConfig.getThreadPool();
????????//拆分數據,拆分5份
????????List>?lists=averageAssign(employeeDOList,?5);
????????//執行的線程
????????Thread?[]threadArray?=?new?Thread[lists.size()];
????????//監控子線程執行完畢,再執行主線程,要不然會導致主線程關閉,子線程也會隨著關閉
????????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?{
?????????????????//最后一個線程拋出異常
????????????????????if?(!atomicBoolean.get()){
????????????????????????throw?new?ServiceException("001","出現異常");
????????????????????}
????????????????????//批量添加,mybatisPlus中自帶的batch方法
????????????????????this.saveBatch(list);
????????????????}finally?{
????????????????????countDownLatch.countDown();
????????????????}

????????????});
????????}
????????for?(int?i?=?0;?i?

	數據庫中存在一條數據：

	
//測試用例
@RunWith(SpringRunner.class)
@SpringBootTest(classes?=?{?ThreadTest01.class,?MainApplication.class})
public?class?ThreadTest01?{

????@Resource
????private?EmployeeBO?employeeBO;

????/**
?????*???測試多線程事務.
?????*?@throws?InterruptedException
?????*/
????@Test
????public??void?MoreThreadTest2()?throws?InterruptedException?{
????????int?size?=?10;
????????List?employeeDOList?=?new?ArrayList<>(size);
????????for?(int?i?=?0;?i

	測試結果：

	

	可以發現子線程組執行時，有一個線程執行失敗，其他線程也會拋出異常，但是主線程中執行的刪除操作，沒有回滾，@Transactional注解沒有生效。

	使用sqlSession控制手動提交事務
?@Resource
??SqlContext?sqlContext;
?/**
?*?測試多線程事務.
?*?@param?employeeDOList
?*/
@Override
public?void?saveThread(List?employeeDOList)?throws?SQLException?{
????//?獲取數據庫連接,獲取會話(內部自有事務)
????SqlSession?sqlSession?=?sqlContext.getSqlSession();
????Connection?connection?=?sqlSession.getConnection();
????try?{
????????//?設置手動提交
????????connection.setAutoCommit(false);
????????//獲取mapper
????????EmployeeMapper?employeeMapper?=?sqlSession.getMapper(EmployeeMapper.class);
????????//先做刪除操作
????????employeeMapper.delete(null);
????????//獲取執行器
????????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);
????????????//使用返回結果的callable去執行,
????????????Callable?callable?=?()?->?{
????????????????//讓最后一個線程拋出異常
????????????????if?(!atomicBoolean.get()){
????????????????????throw?new?ServiceException("001","出現異常");
????????????????}
??????????????return?employeeMapper.saveBatch(list);
????????????};
????????????callableList.add(callable);
????????}
????????//執行子線程
???????List>?futures?=?service.invokeAll(callableList);
????????for?(Future?future:futures)?{
????????//如果有一個執行不成功,則全部回滾
????????????if?(future.get()<=0){
????????????????connection.rollback();
?????????????????return;
????????????}
????????}
????????connection.commit();
????????System.out.println("添加完畢");
????}catch?(Exception?e){
????????connection.rollback();
????????log.info("error",e);
????????throw?new?ServiceException("002","出現異常");
????}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}
?????????)
?????
?

	數據庫中一條數據：

	

	測試結果：拋出異常，

	

	刪除操作的數據回滾了，數據庫中的數據依舊存在，說明事務成功了。

	

	成功操作示例：
?@Resource
SqlContext?sqlContext;
/**
?*?測試多線程事務.
?*?@param?employeeDOList
?*/
@Override
public?void?saveThread(List?employeeDOList)?throws?SQLException?{
????//?獲取數據庫連接,獲取會話(內部自有事務)
????SqlSession?sqlSession?=?sqlContext.getSqlSession();
????Connection?connection?=?sqlSession.getConnection();
????try?{
????????//?設置手動提交
????????connection.setAutoCommit(false);
????????EmployeeMapper?employeeMapper?=?sqlSession.getMapper(EmployeeMapper.class);
????????//先做刪除操作
????????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);
????????}
????????//執行子線程
???????List>?futures?=?service.invokeAll(callableList);
????????for?(Future?future:futures)?{
????????????if?(future.get()<=0){
????????????????connection.rollback();
?????????????????return;
????????????}
????????}
????????connection.commit();
????????System.out.println("添加完畢");
????}catch?(Exception?e){
????????connection.rollback();
????????log.info("error",e);
????????throw?new?ServiceException("002","出現異常");
???????//?throw?new?ServiceException(ExceptionCodeEnum.EMPLOYEE_SAVE_OR_UPDATE_ERROR);
????}
}


	測試結果：

	

	數據庫中數據：

	刪除的刪除了，添加的添加成功了，測試成功。

	

	編輯：黃飛

	?