How to enable request scope in async task executor

We ran into the same problem - needed to execute code in the background using @Async, so it was unable to use any Session- or RequestScope beans. We solved it the following way:

• Create a custom TaskPoolExecutor that stores scoped information with the tasks
• Create a special Callable (or Runnable) that uses the information to set and clear the context for the background thread
• Create an override configuration to use the custom executor

Note: this will only work for Session and Request scoped beans, and not for security context (as in Spring Security). You'd have to use another method to set the security context if that is what you're after.

Note2: For brevity, only shown the Callable and submit() implementation. You can do the same for the Runnable and execute().

Here is the code:

Executor:

public class ContextAwarePoolExecutor extends ThreadPoolTaskExecutor {
    @Override
    public <T> Future<T> submit(Callable<T> task) {
        return super.submit(new ContextAwareCallable(task, RequestContextHolder.currentRequestAttributes()));
    }

    @Override
    public <T> ListenableFuture<T> submitListenable(Callable<T> task) {
        return super.submitListenable(new ContextAwareCallable(task, RequestContextHolder.currentRequestAttributes()));
    }
}

Callable:

public class ContextAwareCallable<T> implements Callable<T> {
    private Callable<T> task;
    private RequestAttributes context;

    public ContextAwareCallable(Callable<T> task, RequestAttributes context) {
        this.task = task;
        this.context = context;
    }

    @Override
    public T call() throws Exception {
        if (context != null) {
            RequestContextHolder.setRequestAttributes(context);
        }

        try {
            return task.call();
        } finally {
            RequestContextHolder.resetRequestAttributes();
        }
    }
}

Configuration:

@Configuration
public class ExecutorConfig extends AsyncConfigurerSupport {
    @Override
    @Bean
    public Executor getAsyncExecutor() {
        return new ContextAwarePoolExecutor();
    }
}

There is no way to get a request scoped object in an child async thread, since the original parent request processing thread may have already committed the response to the client and all the request objects are destroyed. One way to handle such scenarios is to use custom scope, like SimpleThreadScope.

one problem with SimpleThreadScope is that the child threads will not inherit parents scope variables, because it uses simple ThreadLocal internally. To overcome that implement a custom scope which is exactly similar to SimpleThreadScope but uses InheritableThreadLocal internally. For more info reg this Spring MVC: How to use a request-scoped bean inside a spawned thread?

The easiest way is to use a task decorator like this:

static class ContextCopyingDecorator implements TaskDecorator {
    @Nonnull
    @Override
    public Runnable decorate(@Nonnull Runnable runnable) {
        RequestAttributes context =
                RequestContextHolder.currentRequestAttributes();
        Map<String, String> contextMap = MDC.getCopyOfContextMap();
        return () -> {
            try {
                RequestContextHolder.setRequestAttributes(context);
                MDC.setContextMap(contextMap);
                runnable.run();
            } finally {
                MDC.clear();
                RequestContextHolder.resetRequestAttributes();
            }
        };
    }
}

To add this decorator to the task executor, all you need is to add it in the configuration routine:

@Override
@Bean
public Executor getAsyncExecutor() {
    ThreadPoolTaskExecutor poolExecutor = new ThreadPoolTaskExecutor();
    poolExecutor.setTaskDecorator(new ContextCopyingDecorator());
    poolExecutor.initialize();
    return poolExecutor;
}

There is no need for an additional holder or a custom thread-pool task executor.

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A small update for 2021: Using current versions of Spring Boot, the mere existence of a bean of type TaskDecorator will suffice. Upon creating the context, the task decorator will be used to decorate the executors that Spring Boot creates.