How to Preserve Request Scope in Asynchronous Task Execution?

Preserving Request Scope in Asynchronous Task Execution

In an application utilizing asynchronous web services, where the server responds with an acknowledgment while commencing asynchronous processing via an AsyncTaskExecutor, it becomes crucial to enable the request scope. This is essential to access bean classes annotated with @Scope(WebApplicationContext.SCOPE_REQUEST).

Typically, in such scenarios, an exception occurs due to the request scope not being active within the SimpleAsyncTaskExecutor, which operates outside of the DispatcherServlet. To resolve this issue, consider the following solution:

1. Create a Custom Task Executor: Define a custom executor that extends Spring's ThreadPoolTaskExecutor and intercepts execution of submitted tasks.
2. Encapsulate Request Context: Create a specialized Callable (or Runnable) that uses the request context information to set and clear the context on the background thread.
3. Override Execution Configuration: Override the default executor configuration to utilize the custom executor.

Note: This approach only supports Session and Request scoped beans, not security context (e.g., Spring Security). For security context handling, separate measures should be implemented.

Example Implementation:

Executor:

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

Callable:

<code class="java">public class ContextAwareCallable<T> implements Callable<T> {
    private Callable<T> task;
    private RequestAttributes context;
    @Override
    public T call() throws Exception {
        if (context != null) {
            RequestContextHolder.setRequestAttributes(context);
        }
        try {
            return task.call();
        } finally {
            RequestContextHolder.resetRequestAttributes();
        }
    }
}</code>

Configuration:

<code class="java">@Configuration
public class ExecutorConfig extends AsyncConfigurerSupport {
    @Override
    @Bean
    public Executor getAsyncExecutor() {
        return new ContextAwarePoolExecutor();
    }
}</code>

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