为什么@Asynchronous和Future类不起作用

Question

我正在尝试调用返回Future Object的异步方法，我认为它将打印YYY，然后是XXX，因为XXX在一个1秒长的方法中。然而，在部署代码后，它不能正常工作，我用10个对象尝试了同样的事情，它们按顺序打印。错误在哪里？

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package testfuture;


import java.net.InetAddress;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import javax.ejb.Asynchronous;

import javax.ejb.Schedule;
import javax.ejb.Singleton;
import javax.ejb.TransactionManagement;
import javax.ejb.TransactionManagementType;

@Singleton
@TransactionManagement(TransactionManagementType.BEAN)
public class TestFuture {

    @Schedule(minute = "*/1", hour = "*", persistent = false)
    public void start()  {

                try{
                    Future<String> r = inparallelMethod(5) ;
                    System.out.print("YYY");
                    r.get();
                }
                catch ( InterruptedException ie )
                {
                    System.out.print(ie.getMessage());
                }
                catch (ExecutionException e)
                {
                     System.out.print(e.getMessage());
                }


        }

    @Asynchronous
    public Future<String> inparallelMethod(int i) throws InterruptedException
    {

        Thread.sleep(1000);
        System.out.print("XXX");
        return null;
    }


}

Answer 1

因为你在实例化的类中“通过”容器管理调用异步方法来调用inparallelMethod。

您必须在另一个bean中定义异步方法，@Inject该bean并调用该方法。

@Singleton
@TransactionManagement(TransactionManagementType.BEAN)    
public class TestFuture {

    @Inject
    AsyncService service;

    @Schedule(minute = "*/1", hour = "*", persistent = false)
    public void start()  {

                try{
                    Future<String> r = service.inparallelMethod(5) ;
                    System.out.print("YYY");
                    r.get();
                }
                catch ( InterruptedException ie )
                {
                    System.out.print(ie.getMessage());
                }
                catch (ExecutionException e)
                {
                     System.out.print(e.getMessage());
                }


        }
}

@Stateless
public class AsyncService {

    @Asynchronous
    public Future<String> inparallelMethod(int i) throws InterruptedException
    {

        Thread.sleep(1000);
        System.out.print("XXX");
        return null;
    }


}

我张贴的代码使异步工作，但你的代码在非常差的测试异步方案，在java-ee内的Thread.sleep是一个非常糟糕的做法，因为线程是由容器管理的，你不知道哪个线程你真的在睡觉！