Accessing scoped proxy beans within Threads of

问题:

I have a web application running in tomcat where I'm using a ThreadPool (Java 5 ExecutorService) to run IO intensive operations in parallel to improve performance. I would like to have some of the beans used within each pooled thread be in the request scope, but the Threads in the ThreadPool do not have access to the spring context and get a proxy failure. Any ideas on how to make the spring context available to the threads in the ThreadPool to resolve the proxy failures?

I'm guessing there must be a way to register/unregister each thread in the ThreadPool with spring for each task, but haven't had any luck finding how to do this.

Thanks!

回答1:

I am using the following super class for my tasks that need to have access to request scope. Basically you can just extend it and implement your logic in onRun() method.

import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;

/**
 * @author Eugene Kuleshov
 */
public abstract class RequestAwareRunnable implements Runnable {
  private final RequestAttributes requestAttributes;
  private Thread thread;

  public RequestAwareRunnable() {
    this.requestAttributes = RequestContextHolder.getRequestAttributes();
    this.thread = Thread.currentThread();
  }

  public void run() {
    try {
      RequestContextHolder.setRequestAttributes(requestAttributes);
      onRun();
    } finally {
      if (Thread.currentThread() != thread) {
        RequestContextHolder.resetRequestAttributes();
      }
      thread = null;
    }
  }

  protected abstract void onRun();
}

回答2:

I also wish I had 1000 votes to give to the currently accepted answer. I had been stumped on how to do this for some time. Based on it, here is my solution using the Callable interface in case you want to use some of the new @Async stuff in Spring 3.0.

public abstract class RequestContextAwareCallable<V> implements Callable<V> {

    private final RequestAttributes requestAttributes;
    private Thread thread;

    public RequestContextAwareCallable() {
        this.requestAttributes = RequestContextHolder.getRequestAttributes();
        this.thread = Thread.currentThread();
    }

    public V call() throws Exception {
        try {
            RequestContextHolder.setRequestAttributes(requestAttributes);
            return onCall();
        } finally {
            if (Thread.currentThread() != thread) {
                RequestContextHolder.resetRequestAttributes();
            }
            thread = null;
        }
    }

    public abstract V onCall() throws Exception;
}

回答3:

Could you try it the other way round? Use a data container that's stored in request scope and give it to the thread pool (perhaps put it into a queue, so that the thread pool can take one data container at a time, work on it, mark it as "done" and continue with the next one).

回答4:

Spring has a ThreadPoolTaskExecutor class that you can use to manage your thread pool from Spring. However, it looks like you'd have to do some work to make the Spring context available to each thread.

I'm not sure if it will work even if you do wire it up this way though. Spring uses a token in thread local to locate objects in request (or session) scope, so if you're trying to access a request scope bean from a different thread, it's likely that token won't be there.