Local Thread linked with RequestScope

问题

I have a web service built with VRaptor that uses CDI (weld 2.1.2.Final). I need to parallelize some of the processing made by the server (statistical analysis of industrial alarms). I'm doing that using a ExecutorService and Callable instances, unfortunately I need one Request Scoped dependence inside my Threads. Because of that dependence I'm facing this error:

WELD-001303: No active contexts for scope type javax.enterprise.context.RequestScoped

Is there a way to link the Threads to the Request where they were created using CDI?

*I know that I shouldn't be opening threads in the server, but this is the currently most viable option

回答1:

Pass it as constructor argument of the callable.

public class YourTask implements Callable<String> {

    private YourData data;

    public YourTask(YourData data) {
        this.data = data;
    }

    @Override
    public String call() {
        // Just use data.
    }

}

@Inject
private YourRequestScopedBean bean;

public void submit() {
    YourTask task = new YourTask(bean.getData());
    // ...
}

Note: do not pass the bean itself as it's basically a proxy whose instance doesn't exist in other thread.

See also:

• FacesContext.getCurrentInstance() returns null in Runnable class

---

Unrelated to the concrete problem, manually managing threads in a Java EE container, even though when done via a properly programmed ExecutorService, is frowned upon. It indicates you aren't aware of possibilities of Java EE's EJB scheduling and timer APIs. You may find the examples in this answer useful: Is it safe to start a new thread in a JSF managed bean?

来源：https://stackoverflow.com/questions/34815608/local-thread-linked-with-requestscope