先看一个基本的例子
@Path("/produce") public class EventGenerator { @Inject private Logger logger; @Inject private Event<MyEvent> events; @Path("/cdiBean/{eventsNum}") @GET public String generateEvents(@PathParam("eventsNum") int numberOfEventsToGenerate) { for (int i = 0; i < numberOfEventsToGenerate; i++) { MyEvent event = new MyEvent(i); logger.info("Generating Event: " + event); events.fire(event); } return "Finished. Generated " + numberOfEventsToGenerate + " events."; } }MyEvent只是一些事件对象,它在这里不是很重要。
public class EventConsumer { @Inject private Logger logger; public void consumeEvent(@Observes MyEvent myEvent) throws InterruptedException { logger.info("Receiving event: " + myEvent); TimeUnit.MILLISECONDS.sleep(500); } }请注意,我写一个线程睡眠来模拟一些长时间运行的事件接收器模拟复杂费时的处理过程。
14:15:59,196 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=0] 14:15:59,197 [com.piotrnowicki.EventConsumer] (http-/127.0.0.1:8080-1) Receiving event: MyEvent[seqNo=0] 14:15:59,697 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=1] 14:15:59,698 [com.piotrnowicki.EventConsumer] (http-/127.0.0.1:8080-1) Receiving event: MyEvent[seqNo=1] 14:16:00,199 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=2] 14:16:00,200 [com.piotrnowicki.EventConsumer] (http-/127.0.0.1:8080-1) Receiving event: MyEvent[seqNo=2]通过观察,我们可以得到结论,其cdi event默认就是同步的。下面我们将折腾异步的。
我们的生产者保持不变
@Path("/produce") public class EventGenerator { @Path("/cdiBean/{eventsNum}") @GET public String generateEvents(@PathParam("eventsNum") int numberOfEventsToGenerate) { ... } }现在你把接受者设置为 @Singleton EJB,并且标记oberves方法为@Asynchronous
@Singleton public class EventConsumer { @Asynchronous public void consumeEvent(@Observes MyEvent myEvent) throws InterruptedException { ... } }你将得到以下结果
14:21:19,341 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=0] 14:21:19,343 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=1] 14:21:19,343 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=2] 14:21:19,347 [com.piotrnowicki.EventConsumer] (EJB default – 2) Receiving event: MyEvent[seqNo=1] 14:21:19,848 [com.piotrnowicki.EventConsumer] (EJB default – 1) Receiving event: MyEvent[seqNo=0] 14:21:20,350 [com.piotrnowicki.EventConsumer] (EJB default – 3) Receiving event: MyEvent[seqNo=2]事件一个接一个被Singleton EJB在单独的线程处理(看看时间事件处理。), 其实这里的consumeEvent是隐式的write:
这种方法是和解决方案1非常相似的,但是,它提供了高得多的吞吐量,因为所有的事件平行处理。produce仍然不变。
@Path("/produce") public class EventGenerator { @Path("/cdiBean/{eventsNum}") @GET public String generateEvents(@PathParam("eventsNum") int numberOfEventsToGenerate) { ... } }我们的接收者的OB上有@Lock(READ);这使得能够在同一时间服务于多个事件(而在一中是Lock(Write)):
@Singleton public class EventConsumer { @Asynchronous @Lock(LockType.READ) public void consumeEvent(@Observes MyEvent myEvent) throws InterruptedException { ... } }result:
14:24:44,202 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=0] 14:24:44,204 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=1] 14:24:44,205 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=2] 14:24:44,207 [com.piotrnowicki.EventConsumer] (EJB default – 4) Receiving event: MyEvent[seqNo=0] 14:24:44,207 [com.piotrnowicki.EventConsumer] (EJB default – 6) Receiving event: MyEvent[seqNo=2] 14:24:44,207 [com.piotrnowicki.EventConsumer] (EJB default – 5) Receiving event: MyEvent[seqNo=1]
因此,我们结论是,这样的写法给你更大的吞吐量.
异步:是
Ob方法是线程安全的:不是
public class EventConsumer { public void consumeEvent(@Observes(during = TransactionPhase.AFTER_COMPLETION) MyEvent myEvent) { ... } }
现在我们只需要确认我们在Event Generator方法运行的事务。我们可以通过改变我们的CDI Bean成为EJB @Stateless 和使用其隐含的事务--REQUIRED TransactionAttribute:
@Stateless @Path("/produce") public class EventGenerator { @Path("/cdiBean/{eventsNum}") @GET public String generateEvents(@PathParam("eventsNum") int numberOfEventsToGenerate) { ... } }
结果:
14:39:06,776 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=0] 14:39:06,776 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=1] 14:39:06,776 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=2] 14:39:06,778 [com.piotrnowicki.EventConsumer] (http-/127.0.0.1:8080-1) Receiving event: MyEvent[seqNo=2] 14:39:07,279 [com.piotrnowicki.EventConsumer] (http-/127.0.0.1:8080-1) Receiving event: MyEvent[seqNo=1] 14:39:07,780 [com.piotrnowicki.EventConsumer] (http-/127.0.0.1:8080-1) Receiving event: MyEvent[seqNo=0]EJB Event Generator启动一个事务,CDI bean的观察者将在事务完成后,才可以调用。
Asynchronous: yes
Thread-safe observer method: yes
@Stateless @Path("/produce") public class EventGenerator { @Path("/cdiBean/{eventsNum}") @GET public String generateEvents(@PathParam("eventsNum") int numberOfEventsToGenerate) { ... } }
但是更改了观察者方法
@Singleton public class EventConsumer { @Asynchronous @Lock(LockType.READ) public void consumeEvent(@Observes(during = TransactionPhase.AFTER_COMPLETION) MyEvent myEvent) throws InterruptedException { ... } }
result
14:44:09,363 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=0] 14:44:09,464 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=1] 14:44:09,564 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=2] 14:44:09,670 [com.piotrnowicki.EventConsumer] (EJB default – 8) Receiving event: MyEvent[seqNo=2] 14:44:09,670 [com.piotrnowicki.EventConsumer] (EJB default – 2) Receiving event: MyEvent[seqNo=1] 14:44:09,670 [com.piotrnowicki.EventConsumer] (EJB default – 1) Receiving event: MyEvent[seqNo=0]我们在这里使用的两个特点 - 一是该事件消费者的方法是异步的,第二个是生产者事务完成之前,消费者将不会通知。
Solution 2 (@Observes) 15:01:34,318 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=0] 15:01:34,320 [com.piotrnowicki.EventConsumer] (EJB default – 3) Receiving event: MyEvent[seqNo=0] 15:01:34,419 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=1] 15:01:34,420 [com.piotrnowicki.EventConsumer] (EJB default – 6) Receiving event: MyEvent[seqNo=1] 15:01:34,520 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=2] 15:01:34,521 [com.piotrnowicki.EventConsumer] (EJB default – 9) Receiving event: MyEvent[seqNo=2] Solution 4 (@Observes(during = TransactionPhase.AFTER_COMPLETION)) 15:00:41,126 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=0] 15:00:41,226 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=1] 15:00:41,326 [com.piotrnowicki.EventGenerator] (http-/127.0.0.1:8080-1) Generating Event: MyEvent[seqNo=2] 15:00:41,432 [com.piotrnowicki.EventConsumer] (EJB default – 10) Receiving event: MyEvent[seqNo=2] 15:00:41,432 [com.piotrnowicki.EventConsumer] (EJB default – 4) Receiving event: MyEvent[seqNo=1] 15:00:41,432 [com.piotrnowicki.EventConsumer] (EJB default – 5) Receiving event: MyEvent[seqNo=0]
@Stateless @Path("/produce") public class EventGenerator { // ... @Resource private SessionContext sctx; @Path("/cdiBean/{eventsNum}") @GET public String generateEvents(@PathParam("eventsNum") int numberOfEventsToGenerate) { for (int i = 0; i < numberOfEventsToGenerate; i++) { sctx.getBusinessObject(EventGenerator.class).fireEvent(new MyEvent(i)); } return "Finished. Generated " + numberOfEventsToGenerate + " events."; } @Asynchronous public void fireEvent(final MyEvent event) { events.fire(event); } }仔细看看EJB使用sessioncontext。在此情况下,因为我们希望在容器派遣我们方法的调用,并添加了它的异步性质。我们不希望使之成为本地呼叫,所以我们拒绝使用隐含此对象。
public class EventConsumer { public void consumeEvent(@Observes MyEvent myEvent) throws InterruptedException { ... } }
00:40:32,820 [com.piotrnowicki.EventGenerator] (EJB default – 2) Generating Event: MyEvent[seqNo=1] 00:40:32,820 [com.piotrnowicki.EventGenerator] (EJB default – 3) Generating Event: MyEvent[seqNo=2] 00:40:32,820 [com.piotrnowicki.EventGenerator] (EJB default – 1) Generating Event: MyEvent[seqNo=0] 00:40:32,821 [com.piotrnowicki.EventConsumer] (EJB default – 1) Receiving event: MyEvent[seqNo=0] 00:40:32,821 [com.piotrnowicki.EventConsumer] (EJB default – 2) Receiving event: MyEvent[seqNo=1] 00:40:32,821 [com.piotrnowicki.EventConsumer] (EJB default – 3) Receiving event: MyEvent[seqNo=2]Asynchronous: yes