支付寶：多線程事務怎麼回滾？說用 -Transactional 可以回去等通知了！
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，然後在執行插入操作，由於插入數據可能會很多，用到多線程去拆分數據並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註解去控制事務，使出現異常時會進行回滾，在多線程中，這個註解則不會生效，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 <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();
}
}示例事務不成功操作
/**
* 測試多線程事務.
* @param employeeDOList
*/
@Override
@Transactional
public void saveThread(List<EmployeeDO> 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<List<EmployeeDO>> 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,子線程也會隨着關閉
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 {
//最後一個線程拋出異常
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 <lists.size(); i++){
service.execute(threadArray[i]);
}
//當子線程執行完畢時,主線程再往下執行
countDownLatch.await();
System.out.println("添加完畢");
}catch (Exception e){
log.info("error",e);
throw new ServiceException("002","出現異常");
}finally {
connection.close();
}
}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<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註解沒有生效。
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<EmployeeDO> 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<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);
//使用返回結果的callable去執行,
Callable<Integer> callable = () -> {
//讓最後一個線程拋出異常
if (!atomicBoolean.get()){
throw new ServiceException("001","出現異常");
}
return employeeMapper.saveBatch(list);
};
callableList.add(callable);
}
//執行子線程
List<Future<Integer>> futures = service.invokeAll(callableList);
for (Future<Integer> 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 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<EmployeeDO> 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<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。
本文由 Readfog 進行 AMP 轉碼，版權歸原作者所有。
來源：https://mp.weixin.qq.com/s/qT63K3G0-ncIV5gRkVR5AA