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點(diǎn)擊關(guān)注公眾號，Java干貨 及時送達(dá)

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Spring Cloud 2022 正式發(fā)布！

背景介紹

1，最近有一個大數(shù)據(jù)量插入的操作入庫的業(yè)務(wù)場景，需要先做一些其他修改操作，然后在執(zhí)行插入操作，由于插入數(shù)據(jù)可能會很多，用到多線程去拆分?jǐn)?shù)據(jù)并行處理來提高響應(yīng)時間，如果有一個線程執(zhí)行失敗，則全部回滾。

2，在spring中可以使用@Transactional注解去控制事務(wù)，使出現(xiàn)異常時會進(jìn)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(zhí)行一些修改數(shù)據(jù)庫的操作，當(dāng)子線程在進(jìn)行處理出現(xiàn)異常時，主線程修改的數(shù)據(jù)則不會回滾，導(dǎo)致數(shù)據(jù)錯誤。

3，下面用一個簡單示例演示多線程事務(wù)。

公用的類和方法

      
      /**
?*?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=new?ArrayList<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;
}
/**??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();
????}
}

另外，如果你近期準(zhǔn)備面試跳槽，建議在 Java面試庫小程序在線刷題，涵蓋 2000+?道 Java 面試題，幾乎覆蓋了所有主流技術(shù)面試題。

示例事務(wù)不成功操作

      
      ??/**
?*?測試多線程事務(wù).
?*?@param?employeeDOList
?*/
@Override
@Transactional
public?void?saveThread(List<EmployeeDO>?employeeDOList)?{
????try?{
????????//先做刪除操作,如果子線程出現(xiàn)異常,此操作不會回滾
????????this.getBaseMapper().delete(null);
????????//獲取線程池
????????ExecutorService?service?=?ExecutorConfig.getThreadPool();
????????//拆分?jǐn)?shù)據(jù),拆分5份
????????List<List<EmployeeDO>>?lists=averageAssign(employeeDOList,?5);
????????//執(zhí)行的線程
????????Thread?[]threadArray?=?new?Thread[lists.size()];
????????//監(jiān)控子線程執(zhí)行完畢,再執(zhí)行主線程,要不然會導(dǎo)致主線程關(guān)閉,子線程也會隨著關(guān)閉
????????CountDownLatch?countDownLatch?=?new?CountDownLatch(lists.size());
????????AtomicBoolean?atomicBoolean?=?new?AtomicBoolean(true);
????????for?(int?i?=0;i<lists.size();i++){
????????????if?(i==lists.size()-1){
????????????????atomicBoolean.set(false);
????????????}
????????????List<EmployeeDO>?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(xiàn)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?<lists.size();?i++){
????????????service.execute(threadArray[i]);
????????}
????????//當(dāng)子線程執(zhí)行完畢時,主線程再往下執(zhí)行
????????countDownLatch.await();
????????System.out.println("添加完畢");
????}catch?(Exception?e){
????????log.info("error",e);
????????throw?new?ServiceException("002","出現(xiàn)異常");
????}finally?{
?????????connection.close();
?????}
}

數(shù)據(jù)庫中存在一條數(shù)據(jù)：

Spring Boot 基礎(chǔ)就不介紹了，推薦下這個實(shí)戰(zhàn)教程：https://github.com/javastacks/spring-boot-best-practice

      
      //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(wù).
?????*?@throws?InterruptedException
?????*/
????@Test
????public??void?MoreThreadTest2()?throws?InterruptedException?{
????????int?size?=?10;
????????List<EmployeeDO>?employeeDOList?=?new?ArrayList<>(size);
????????for?(int?i?=?0;?i<size;i++){
????????????EmployeeDO?employeeDO?=?new?EmployeeDO();
????????????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();
????????}
????}
}

測試結(jié)果：

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

點(diǎn)擊關(guān)注公眾號，Java干貨 及時送達(dá)

使用sqlSession控制手動提交事務(wù)

      
      ?@Resource
??SqlContext?sqlContext;
?/**
?*?測試多線程事務(wù).
?*?@param?employeeDOList
?*/
@Override
public?void?saveThread(List<EmployeeDO>?employeeDOList)?throws?SQLException?{
????//?獲取數(shù)據(jù)庫連接,獲取會話(內(nèi)部自有事務(wù))
????SqlSession?sqlSession?=?sqlContext.getSqlSession();
????Connection?connection?=?sqlSession.getConnection();
????try?{
????????//?設(shè)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(zhí)行器
????????ExecutorService?service?=?ExecutorConfig.getThreadPool();
????????List<Callable<Integer>>?callableList??=?new?ArrayList<>();
????????//拆分list
????????List<List<EmployeeDO>>?lists=averageAssign(employeeDOList,?5);
????????AtomicBoolean?atomicBoolean?=?new?AtomicBoolean(true);
????????for?(int?i?=0;i<lists.size();i++){
????????????if?(i==lists.size()-1){
????????????????atomicBoolean.set(false);
????????????}
????????????List<EmployeeDO>?list??=?lists.get(i);
????????????//使用返回結(jié)果的callable去執(zhí)行,
????????????Callable<Integer>?callable?=?()?->?{
????????????????//讓最后一個線程拋出異常
????????????????if?(!atomicBoolean.get()){
????????????????????throw?new?ServiceException("001","出現(xiàn)異常");
????????????????}
??????????????return?employeeMapper.saveBatch(list);
????????????};
????????????callableList.add(callable);
????????}
????????//執(zhí)行子線程
???????List<Future<Integer>>?futures?=?service.invokeAll(callableList);
????????for?(Future<Integer>?future:futures)?{
????????//如果有一個執(zhí)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(xiàn)異常");
????}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>

數(shù)據(jù)庫中一條數(shù)據(jù)：

測試結(jié)果：拋出異常，

刪除操作的數(shù)據(jù)回滾了，數(shù)據(jù)庫中的數(shù)據(jù)依舊存在，說明事務(wù)成功了。

另外，如果你近期準(zhǔn)備面試跳槽，建議在 Java面試庫小程序在線刷題，涵蓋 2000+?道 Java 面試題，幾乎覆蓋了所有主流技術(shù)面試題。

成功操作示例：

      ?@Resource
SqlContext?sqlContext;
/**
?*?測試多線程事務(wù).
?*?@param?employeeDOList
?*/
@Override
public?void?saveThread(List<EmployeeDO>?employeeDOList)?throws?SQLException?{
????//?獲取數(shù)據(jù)庫連接,獲取會話(內(nèi)部自有事務(wù))
????SqlSession?sqlSession?=?sqlContext.getSqlSession();
????Connection?connection?=?sqlSession.getConnection();
????try?{
????????//?設(shè)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<Callable<Integer>>?callableList??=?new?ArrayList<>();
????????List<List<EmployeeDO>>?lists=averageAssign(employeeDOList,?5);
????????for?(int?i?=0;i<lists.size();i++){
????????????List<EmployeeDO>?list??=?lists.get(i);
????????????Callable<Integer>?callable?=?()?->?employeeMapper.saveBatch(list);
????????????callableList.add(callable);
????????}
????????//執(zhí)行子線程
???????List<Future<Integer>>?futures?=?service.invokeAll(callableList);
????????for?(Future<Integer>?future:futures)?{
????????????if?(future.get()<=0){
????????????????connection.rollback();
?????????????????return;
????????????}
????????}
????????connection.commit();
????????System.out.println("添加完畢");
????}catch?(Exception?e){
????????connection.rollback();
????????log.info("error",e);
????????throw?new?ServiceException("002","出現(xiàn)異常");
???????//?throw?new?ServiceException(ExceptionCodeEnum.EMPLOYEE_SAVE_OR_UPDATE_ERROR);
????}
}

測試結(jié)果：

數(shù)據(jù)庫中數(shù)據(jù)：

刪除的刪除了，添加的添加成功了，測試成功。

版權(quán)聲明：本文為CSDN博主「weixin_43225491」的原創(chuàng)文章，遵循CC 4.0 BY-SA版權(quán)協(xié)議，轉(zhuǎn)載請附上原文出處鏈接及本聲明。原文鏈接：https://blog.csdn.net/weixin_43225491/article/details/117705686

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支付寶一面:多線程事務(wù)怎么回滾?說用 @Transactional 可以回去等...

背景介紹

公用的類和方法

示例事務(wù)不成功操作