Guice 在执行 CompletableFuture 时抛出 OutOfScopeException

Question

在请求范围的线程中，CompletableFutures 必须由执行程序中的任务运行完成。提供的供应商使用会话范围内的域特定服务 MessageService。该服务由 Guice 注入。

public class MessageProcessingPage {
    private MessageService messageService;

    @Inject
    public MessagProcessingPage (MessageService messageService) {
        this.messageService = messageService;
    }

    // Called by request scoped thread.
    public void onProcessMessagesButton () {
        ExecutorService executorService = Executors.newFixedThreadPool(3);
        CompletableFuture.supplyAsync(
        // Called from a thread from the threadpool.
        () -> {return messageService.retrieveMessageMetadataSet(x, y);}
        , executorService);

        ...

    }

    ...
}

MessageService 有一个（会话范围的）MessageRestClient 被注入。

@SessionScoped
public class MessageService {
    private MessageRestClient messageRestClient;

    @Inject
    public MessageRestClient (MessageRestClient messageRestClient) {
        this.messageRestClient = messageRestClient;
    }

    public MessageMetaDataSet retrieveMessageMetadataSet(x, y) {
        List<MessageMetaData> listOfMetaData = messageRestClient.retrieve(x, y, z);
        ...
    }

    ...
}

@SessionScoped
public class MessageRestClient {
    ...
}

Guice 在尝试注入 MessageRestClient 时遇到了麻烦。

java.util.concurrent.CompletionException: com.google.inject.ProvisionException: Unable to provision, see the following errors:

1) Error in custom provider, com.google.inject.OutOfScopeException: Cannot access scoped [MessageRestClient]. Either we are not currently inside an HTTP Servlet request, or you may have forgotten to apply com.google.inject.servlet.GuiceFilter as a servlet filter for this request.

我在 ServletScopes 中读到一个方法：public static <T> Callable<T> transferRequest(Callable<T> callable) 但我看不到使用它的方法，因为没有 Callables 参与进来。你能帮我解决一下吗？

Answer 1

在 Guice 中处理 servlet 请求时，GuiceFilter 已负责设置正确的上下文（通过 ThreadLocal），以便它可以知道您在哪个请求中因此，正确应用范围。用 SessionScope 注释的类的实例实际上是代理可以从 Guice 访问该请求和会话信息并采取相应的行动。

您发送给 CompletableFuture 的任务在不受 Guice 控制的单独线程中运行。 Guice 可以从中获取该信息的地方没有 ThreadLocal，因此，没有 Request 和 Session 信息，什么意思，没有 [SessionScope .由于代理对会话一无所知，因此它会抛出您遇到的错误。

ServletScopes.transferRequest 方法应该注入所需的信息，以便作用域起作用。应该像这样工作（但从未尝试过）：

   Callable<MessageMetaDataSet> c = ServletScopes.transferRequest(
               () -> messageService.retrieveMessageMetadataSet(x, y));

   CompletableFuture.supplyAsync(
    () -> c.call()
    , executorService);

Answer 2

尽早尝试：Guice @Inject 一切正常：



    import java.util.concurrent.CompletableFuture;

    public class AsyncFire {

        public static > void execAsync(Class asyncClass) {
            T asyncInstance = AsyncInjector.getInjector().getInstance(asyncClass); <b>//magic</b>
            CompletableFuture completableFuture = CompletableFuture.supplyAsync(asyncInstance); //business logic
            completableFuture.exceptionally(asyncInstance); //if error
            completableFuture.thenAccept(asyncInstance); //if success
        }

    }



    public class ExampleAsync extends Async {

        @Inject <b>//it works</b>
        private EntityManager entityManager;

        @Inject <b>//it works</b>
        private DAO dao; //your

    }



    import java.util.function.Consumer;
    import java.util.function.Function;
    import java.util.function.Supplier;

    public abstract class Async implements Supplier, Consumer, Function {
        //...
    }



    import com.google.inject.Guice;
    import com.google.inject.Injector;
    import com.google.inject.persist.PersistService;

    public final class AsyncInjector {

        private static Injector injector = null; 

        public static Injector getInjector() {
            if (injector == null) {
                synchronized (AsyncInjector.class) {
                    if (injector == null) {
                        injector = Guice.createInjector(new MyGuiceModule()); <b>//your guice module</b>
                        PersistService service = injector.getInstance(PersistService.class);
                        service.start();
                    }
                }
            }
            return injector;
        }

    }

希望这对某人有所帮助！

Guice 在执行 CompletableFuture 时抛出 OutOfScopeException

Guice throwing OutOfScopeException when executing CompletableFuture

java

guice

completable-future