使用线程池时，多线程之间上下文参数传递失效解决办法

Posted 2023-01-13 抓手

问题描述

在执行业务代码时，有时候需要异步处理一些业务，在异步线程中获取当前登录的用户信息失败。因为用户信息是在过滤器或拦截器中解析出来并设置到ThreadLocal中的，子线程是无法获取到ThreadLocal中的值的。
虽然可以使用InheritableThreadLocal替代ThreadLocal，但是只能在新创建的线程中使用。对于线程池也会失效，因为线程池中的线程是由线程池创建好并可重复利用，这时InheritableThreadLocal的值传递就失去意义了。

解决办法

自定义线程池和线程池执行器，重写submit方法，抓取主线程中的用户信息然后在子线程中回放，在子线程执行完业务逻辑后，清除用户信息。

定义当前登录用户信息类

import lombok.Data;

/**
 * @author 向振华
 * @date 2023/01/12 10:40
 */
public class CurrentUser 

    private CurrentUser() 
    

    public static final ThreadLocal<UserInfo> CURRENT_USER = new ThreadLocal<>();

    public static UserInfo get() 
        return CURRENT_USER.get();
    

    public static void set(UserInfo userInfo) 
        CURRENT_USER.set(userInfo);
    

    public static void clear() 
        CURRENT_USER.remove();
    

    @Data
    public static class UserInfo 
        private Long userId;
        private String name;
        private String mobile;
    

定义可传递上下文信息的ThreadPoolExecutor

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.*;

/**
 * @author 向振华
 * @date 2023/01/12 10:40
 */
@Slf4j
public class TransmittableThreadPoolExecutor extends ThreadPoolExecutor 

    public TransmittableThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) 
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
    

    public TransmittableThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory) 
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory);
    

    public TransmittableThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler) 
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);
    

    public TransmittableThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) 
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
    

    @Override
    public void execute(Runnable task) 
        super.execute(this.wrapRunnable(task));
    

    @Override
    public <T> Future<T> submit(Runnable task, T result) 
        return super.submit(this.wrapRunnable(task), result);
    

    @Override
    public <T> Future<T> submit(Callable<T> task) 
        return super.submit(this.wrapCallable(task));
    

    @Override
    public Future<?> submit(Runnable task) 
        return super.submit(this.wrapRunnable(task));
    

    public Runnable wrapRunnable(final Runnable runnable) 
        final CurrentUser.UserInfo userInfo = CurrentUser.get();
        return () -> 
            CurrentUser.set(userInfo);
            try 
                runnable.run();
             catch (Exception e) 
                log.error("异常 ", e);
                throw e;
             finally 
                CurrentUser.clear();
            
        ;
    

    public <T> Callable<T> wrapCallable(final Callable<T> callable) 
        final CurrentUser.UserInfo userInfo = CurrentUser.get();
        return () -> 
            CurrentUser.set(userInfo);
            try 
                return callable.call();
             catch (Exception e) 
                log.error("异常 ", e);
                throw e;
             finally 
                CurrentUser.clear();
            
        ;
    

定义线程池获取工具类

import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;

import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author 向振华
 * @date 2023/01/12 10:40
 */
@Component
public class ExecutorUtils implements ApplicationListener<ContextRefreshedEvent> 

    private static ExecutorService asyncExecutorService;

    private ExecutorUtils() 
    

    public static ExecutorService getAsyncExecutorService() 
        return asyncExecutorService;
    

    /**
     * 初始化线程池
     */
    private static void init() 
        if (asyncExecutorService == null) 
            AtomicInteger threadNumber = new AtomicInteger(0);
            asyncExecutorService = new TransmittableThreadPoolExecutor(
                    3,
                    3,
                    60,
                    TimeUnit.SECONDS,
                    new ArrayBlockingQueue<>(16),
                    new ThreadFactory() 
                        @Override
                        public Thread newThread(Runnable r) 
                            return new Thread(r, "async-exec-" + threadNumber.getAndIncrement());
                        
                    ,
                    new RejectedExecutionHandler() 
                        @Override
                        public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) 
                            if (!executor.isShutdown()) 
                                try 
                                    //尝试阻塞式加入任务队列
                                    executor.getQueue().put(r);
                                 catch (InterruptedException e) 
                                    //保持线程的中端状态
                                    Thread.currentThread().interrupt();
                                
                            
                        
                    );
        
    

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) 
        init();
    

使用方法

开启异步调用： 

ExecutorUtils.getAsyncExecutorService().submit(() -> testService.doSomething());

注意：需要提前在过滤器或拦截器中解析出用户信息并设置到CurrentUser类中，或者提前在主线程中设置用户信息。然后可以在主线程、子线程直接获取用户信息：

CurrentUser.UserInfo userInfo = CurrentUser.get();

其他解决办法

使用阿里的开源工具：transmittable-thread-local

GitHub - alibaba/transmittable-thread-local: 📌 TransmittableThreadLocal (TTL), the missing Java™ std lib(simple & 0-dependency) for framework/middleware, provide an enhanced InheritableThreadLocal that transmits values between threads even using thread pooling components.