spring 使用多线程，保证事务一致性

1、背景

最近接受到接口优化的任务，查看代码逻辑后发现在批量处理数据耗时长，想到使用多线程处理批量数据，又要保持原来的事务一致性。

2、实现方法

（1）、创建多线程事务管理

java 复制代码

@Component
@Slf4j
public class MultiThreadingTransactionManager {
    /**
     * 数据源事务管理器
     */
    @Autowired
    private DataSourceTransactionManager dataSourceTransactionManager;
    @Autowired
    private ThreadPoolTaskExecutor executorService;
    private long timeout = 120;

    /**
     * 用于判断子线程业务是否处理完成
     * 处理完成时threadCountDownLatch的值为0
     */
    private CountDownLatch threadCountDownLatch;

    /**
     * 用于等待子线程全部完成后,子线程统一进行提交和回滚
     * 进行提交和回滚时mainCountDownLatch的值为0
     */
    private final CountDownLatch mainCountDownLatch = new CountDownLatch(1);

    /**
     * 是否提交事务,默认是true,当子线程有异常发生时,设置为false,回滚事务
     */
    private final AtomicBoolean isSubmit = new AtomicBoolean(true);

    public boolean execute(List<Runnable> runnableList,String factorySchema) {
        isSubmit.set(true);
        setThreadCountDownLatch(runnableList.size());
        runnableList.forEach(runnable -> executorService.execute(() -> executeThread(factorySchema,runnable, threadCountDownLatch, mainCountDownLatch, isSubmit)));
        // 等待子线程全部执行完毕
        try {
            // 若计数器变为零了,则返回 true
            boolean isFinish = threadCountDownLatch.await(timeout, TimeUnit.SECONDS);
            if (!isFinish) {
                // 如果还有为执行完成的就回滚
                isSubmit.set(false);
                log.info("存在子线程在预期时间内未执行完毕,任务将全部回滚");
            }
        } catch (Exception exception) {
            log.info("主线程发生异常,异常为: " + exception.getMessage());
        } finally {
            // 计数器减1,代表该主线程执行完毕
            mainCountDownLatch.countDown();
        }
        // 返回结果,是否执行成功,事务提交即为执行成功,事务回滚即为执行失败
        return isSubmit.get();
    }

    private void executeThread(String factorySchema,Runnable runnable, CountDownLatch threadCountDownLatch, CountDownLatch mainCountDownLatch, AtomicBoolean isSubmit) {
        log.info("子线程: [" + Thread.currentThread().getName() + "]");
        // 判断别的子线程是否已经出现错误,错误别的线程已经出现错误,那么所有的都要回滚,这个子线程就没有必要执行了
        if (!isSubmit.get()) {
            log.info("整个事务中有子线程执行失败需要回滚, 子线程: [" + Thread.currentThread().getName() + "] 终止执行");
            // 计数器减1,代表该子线程执行完毕
            threadCountDownLatch.countDown();
            return;
        }
        //动态数据源切换
        SchemaContextHolder.setSchema(factorySchema);
        // 开启事务
        DefaultTransactionDefinition defaultTransactionDefinition = new DefaultTransactionDefinition();
        TransactionStatus transactionStatus = dataSourceTransactionManager.getTransaction(defaultTransactionDefinition);
        try {
            // 执行业务逻辑
            runnable.run();
        } catch (Exception exception) {
            // 发生异常需要进行回滚,设置isSubmit为false
            isSubmit.set(false);
            log.info("子线程: [" + Thread.currentThread().getName() + "]执行业务发生异常,异常为: " + exception.getMessage());
        } finally {
            // 计数器减1,代表该子线程执行完毕
            threadCountDownLatch.countDown();
        }
        try {
            // 等待主线程执行
            mainCountDownLatch.await();
        } catch (Exception exception) {
            log.info("子线程: [" + Thread.currentThread().getName() + "]等待提交或回滚异常,异常为: " + exception.getMessage());
        }
        try {
            // 提交
            if (isSubmit.get()) {
                dataSourceTransactionManager.commit(transactionStatus);
                log.info("子线程: [" + Thread.currentThread().getName() + "]进行事务提交");
            } else {
                dataSourceTransactionManager.rollback(transactionStatus);
                log.info("子线程: [" + Thread.currentThread().getName() + "]进行事务回滚");
            }
        } catch (Exception exception) {
            log.info("子线程: [" + Thread.currentThread().getName() + "]进行事务提交或回滚出现异常,异常为:" + exception.getMessage());
        }
    }

    private void setThreadCountDownLatch(int num) {
        this.threadCountDownLatch = new CountDownLatch(num);
    }
}

（2）、测试类

java 复制代码

@RestController
@RequestMapping("test")
public class TestController {
    @Autowired
    TestService testService;
    @Autowired
    MultiThreadingTransactionManager multiThreadingTransactionManager;
    @RequestMapping("test")
    public String test(){
        List<TestBean> list = new ArrayList<>();
        list.add(new TestBean("2",1));
        list.add(new TestBean("3",2));
        List<Runnable> runnableList = new ArrayList<>();
        list.forEach(testBean -> runnableList.add(() -> {
                testService.insert(testBean);
        }));
        boolean isSuccess = multiThreadingTransactionManager.execute(runnableList,"db9771");
        System.out.println(isSuccess);

        return "ok";
    };
}

3、总结

大体思路，就是所有子线程在各自线程内开启事务，执行业务逻辑后，判断是否抛错，一旦抛错，会把全局AtomicBoolean置为false，因为其具有原子性所以不会有线程不安全问题。所有子线程完业务代码会等待主线程，全部子线程执行业务结束后，主线程等待结束，判断AtomicBoolean是什么状态，一旦false,所有子线程回滚，否则提交。