Spring promoting request scoped bean to child threads (HttpServletRequest)

问题

I tried a lot of things now but i seem to miss a piece of the puzzle. Here is the story: I have a request scoped bean that reads some SessionContext from the HttpServletRequest. This attribute is set in a filter. So this is working absolutely fine while the code runs on the correct thread.

@Component
@Scope(value = WebApplicationContext.SCOPE_REQUEST, proxyMode = ScopedProxyMode.INTERFACES)
public class SessionContextProviderImpl implements SessionContextProvider<SessionContext> {
    private final HttpServletRequest _request;

    @Autowired
    public SessionContextProviderImpl(HttpServletRequest request) {
        _request = request;
    }

    @Override
    public SessionContext get() {
        return (SessionContext) _request.getAttribute(Constants.SESSION_CONTEXT_IDENTIFIER);
    }
}

Now I started using java 8s new feature CompletableFuture and i have three of those features computing stuff in parallel while the request thread waits for the result. What i want to do is to promote/hand over/propagate the bean or request in a way that it can be used on child threads that have been spawned from the original http thread. In particular I would like to get the SessionContext from the HttpServletRequest from inside an asynchronous supplied CompletableFuture.

what i tried is this (replaced implementation of get):

final HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
request.getAttribute(Constants.SESSION_CONTEXT_IDENTIFIER);

But this has obviously the same result as the request scoped bean. Well "getRequest" returns null instead of an exception thrown.

As a third approach I tried this original post:

ConfigurableBeanFactory cbf = (ConfigurableBeanFactory) beanFactory;

org.springframework.beans.factory.config.Scope simpleThreadScope = new SimpleThreadScope();

cbf.registerScope("simpleThreadScope", simpleThreadScope);

And i set the scope of the SessionContextProviderImpl to be "simpleThreadScope". Unfortunately this did not work either and threw an exception that it is used outside of a request scope.

The environment I am using: Jersey together with spring injection.

Maybe anyone has some idea?

regards

回答1:

For any future adventurers:

I took some time to dig through the Spring code and found RequestContextHolder that has a inheritableRequestAttributesHolder. If you look at the documentation of what that is (inheriting from: InheritableThreadLocal) one can read the following:

Inheritable thread-local variables are used in preference to ordinary thread-local variables when the per-thread-attribute being maintained in the variable (e.g., User ID, Transaction ID) must be automatically transmitted to any child threads that are created.

So the RequestContextHolder has a field for that and actually setRequestAttributes supports a flag to use inheritableRequestAttributesHolder. Furthermore if you look at RequestContextListener -> requestInitialized you find that it is called without the flag (= false). So what I ended up doing is this:

public class InheritableRequestContextListener extends RequestContextListener {
    private static final String REQUEST_ATTRIBUTES_ATTRIBUTE =
        InheritableRequestContextListener.class.getName() + ".REQUEST_ATTRIBUTES";

    @Override
    public void requestInitialized(ServletRequestEvent requestEvent) {
        if (!(requestEvent.getServletRequest() instanceof HttpServletRequest)) {
            throw new IllegalArgumentException(
                    "Request is not an HttpServletRequest: " + requestEvent.getServletRequest());
        }
        HttpServletRequest request = (HttpServletRequest) requestEvent.getServletRequest();
        ServletRequestAttributes attributes = new ServletRequestAttributes(request);
        request.setAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE, attributes);
        LocaleContextHolder.setLocale(request.getLocale());
        RequestContextHolder.setRequestAttributes(attributes, true);
    }
}

And voila, I can access SessionContextProvider in child threads.

回答2:

In my case using OrderedRequestContextFilter resolve the issue. You have to also set threadContextInheritable flag to true like this :

@Bean
public RequestContextFilter requestContextFilter() {
    OrderedRequestContextFilter filter = new OrderedRequestContextFilter();
    filter.setThreadContextInheritable(true);
    return filter;
}

来源：https://stackoverflow.com/questions/37540466/spring-promoting-request-scoped-bean-to-child-threads-httpservletrequest