How to access request-scoped beans within asynchronous task execution?

How to Maintain Request Scope in Asynchronous Task Execution

In web applications, it is common to perform asynchronous operations that require the use of beans with request scope. Enabling request scope in asynchronous task execution can be achieved by implementing a custom task executor.

Problem:

You have asynchronous web services that initiate processing in an AsyncTaskExecutor. However, you need to access classes annotated with @Scope(value = WebApplicationContext.SCOPE_REQUEST, proxyMode = ScopedProxyMode.TARGET_CLASS) within this processing. However, you receive an exception because the request scope is not active in the SimpleAsyncTaskExecutor.

Solution:

To enable request scope in the asynchronous task execution, we will implement the following steps:

1. Create a Custom TaskExecutor:

   <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>

2. Implement a Context-Aware Callable:

   <code class="java">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();
           }
       }
   }</code>

3. Configure the Custom TaskExecutor:

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

Explanation:

The ContextAwarePoolExecutor intercepts submitted tasks and wraps them in ContextAwareCallable instances. These callables set the current request context before executing the actual task and reset it afterwards. This ensures that the request-scoped beans are accessible during the asynchronous execution.

Note:

• This solution works for both session-scoped and request-scoped beans but not for security contexts.
• A runnable implementation can be created and used in place of the callable implementation for the execute() method.

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