Micronaut Context Events

2023-02-27 17:25 更新

Micronaut 通過上下文支持一個通用的事件系統(tǒng)。 ApplicationEventPublisher API 發(fā)布事件，ApplicationEventListener API 用于監(jiān)聽事件。事件系統(tǒng)不限于 Micronaut 發(fā)布的事件，支持用戶創(chuàng)建的自定義事件。

發(fā)布活動

ApplicationEventPublisher API 支持任何類型的事件，盡管 Micronaut 發(fā)布的所有事件都擴(kuò)展了 ApplicationEvent。

要發(fā)布事件，請使用依賴項注入獲取 ApplicationEventPublisher 的實例，其中通用類型是事件類型，并使用您的事件對象調(diào)用 publishEvent 方法。

發(fā)布事件

Java Groovy Kotlin

public class SampleEvent {
    private String message = "Something happened";

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

import io.micronaut.context.event.ApplicationEventPublisher;
import jakarta.inject.Inject;
import jakarta.inject.Singleton;

@Singleton
public class SampleEventEmitterBean {

    @Inject
    ApplicationEventPublisher<SampleEvent> eventPublisher;

    public void publishSampleEvent() {
        eventPublisher.publishEvent(new SampleEvent());
    }

}

class SampleEvent {
    String message = "Something happened"
}

import io.micronaut.context.event.ApplicationEventPublisher
import jakarta.inject.Inject
import jakarta.inject.Singleton

@Singleton
class SampleEventEmitterBean {

    @Inject
    ApplicationEventPublisher<SampleEvent> eventPublisher

    void publishSampleEvent() {
        eventPublisher.publishEvent(new SampleEvent())
    }

}

data class SampleEvent(val message: String = "Something happened")

import io.micronaut.context.event.ApplicationEventPublisher
import jakarta.inject.Inject
import jakarta.inject.Singleton

@Singleton
class SampleEventEmitterBean {

    @Inject
    internal var eventPublisher: ApplicationEventPublisher<SampleEvent>? = null

    fun publishSampleEvent() {
        eventPublisher!!.publishEvent(SampleEvent())
    }

}

默認(rèn)情況下發(fā)布事件是同步的！ publishEvent 方法將在所有偵聽器都已執(zhí)行后才會返回。如果這項工作很耗時，請將其移至線程池。

監(jiān)聽事件

要偵聽事件，請注冊一個實現(xiàn) ApplicationEventListener 的 bean，其中通用類型是事件的類型。

使用 ApplicationEventListener 監(jiān)聽事件

Java Groovy Kotlin

import io.micronaut.context.event.ApplicationEventListener;
import io.micronaut.docs.context.events.SampleEvent;
import jakarta.inject.Singleton;

@Singleton
public class SampleEventListener implements ApplicationEventListener<SampleEvent> {
    private int invocationCounter = 0;

    @Override
    public void onApplicationEvent(SampleEvent event) {
        invocationCounter++;
    }

    public int getInvocationCounter() {
        return invocationCounter;
    }
}

import io.micronaut.context.ApplicationContext;
import io.micronaut.docs.context.events.SampleEventEmitterBean;
import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class SampleEventListenerSpec {

    @Test
    public void testEventListenerIsNotified() {
        try (ApplicationContext context = ApplicationContext.run()) {
            SampleEventEmitterBean emitter = context.getBean(SampleEventEmitterBean.class);
            SampleEventListener listener = context.getBean(SampleEventListener.class);
            assertEquals(0, listener.getInvocationCounter());
            emitter.publishSampleEvent();
            assertEquals(1, listener.getInvocationCounter());
        }
    }
}

import io.micronaut.context.event.ApplicationEventListener
import io.micronaut.docs.context.events.SampleEvent
import jakarta.inject.Singleton

@Singleton
class SampleEventListener implements ApplicationEventListener<SampleEvent> {
    int invocationCounter = 0

    @Override
    void onApplicationEvent(SampleEvent event) {
        invocationCounter++
    }
}

import io.micronaut.context.ApplicationContext
import io.micronaut.docs.context.events.SampleEventEmitterBean
import spock.lang.Specification

class SampleEventListenerSpec extends Specification {

    void "test event listener is notified"() {
        given:
        ApplicationContext context = ApplicationContext.run()
        SampleEventEmitterBean emitter = context.getBean(SampleEventEmitterBean)
        SampleEventListener listener = context.getBean(SampleEventListener)

        expect:
        listener.invocationCounter == 0

        when:
        emitter.publishSampleEvent()

        then:
        listener.invocationCounter == 1

        cleanup:
        context.close()
    }
}

import io.micronaut.context.event.ApplicationEventListener
import io.micronaut.docs.context.events.SampleEvent
import jakarta.inject.Singleton

@Singleton
class SampleEventListener : ApplicationEventListener<SampleEvent> {
    var invocationCounter = 0

    override fun onApplicationEvent(event: SampleEvent) {
        invocationCounter++
    }
}

import io.kotest.matchers.shouldBe
import io.kotest.core.spec.style.AnnotationSpec
import io.micronaut.context.ApplicationContext
import io.micronaut.docs.context.events.SampleEventEmitterBean

class SampleEventListenerSpec : AnnotationSpec() {

    @Test
    fun testEventListenerWasNotified() {
        val context = ApplicationContext.run()
        val emitter = context.getBean(SampleEventEmitterBean::class.java)
        val listener = context.getBean(SampleEventListener::class.java)
        listener.invocationCounter.shouldBe(0)
        emitter.publishSampleEvent()
        listener.invocationCounter.shouldBe(1)

        context.close()
    }
}

可以覆蓋 supports 方法以進(jìn)一步闡明要處理的事件。

或者，如果您不想實現(xiàn)接口或不使用 StartupEvent 和 ShutdownEvent 等內(nèi)置事件之一，請使用 @EventListener 注釋：

使用@EventListener 監(jiān)聽事件

Java Groovy Kotlin

import io.micronaut.docs.context.events.SampleEvent;
import io.micronaut.context.event.StartupEvent;
import io.micronaut.context.event.ShutdownEvent;
import io.micronaut.runtime.event.annotation.EventListener;

@Singleton
public class SampleEventListener {
    private int invocationCounter = 0;

    @EventListener
    public void onSampleEvent(SampleEvent event) {
        invocationCounter++;
    }

    @EventListener
    public void onStartupEvent(StartupEvent event) {
        // startup logic here
    }

    @EventListener
    public void onShutdownEvent(ShutdownEvent event) {
        // shutdown logic here
    }

    public int getInvocationCounter() {
        return invocationCounter;
    }
}

import io.micronaut.docs.context.events.SampleEvent
import io.micronaut.context.event.StartupEvent
import io.micronaut.context.event.ShutdownEvent
import io.micronaut.runtime.event.annotation.EventListener

@Singleton
class SampleEventListener {
    int invocationCounter = 0

    @EventListener
    void onSampleEvent(SampleEvent event) {
        invocationCounter++
    }

    @EventListener
    void onStartupEvent(StartupEvent event) {
        // startup logic here
    }

    @EventListener
    void onShutdownEvent(ShutdownEvent event) {
        // shutdown logic here
    }
}

import io.micronaut.docs.context.events.SampleEvent
import io.micronaut.context.event.StartupEvent
import io.micronaut.context.event.ShutdownEvent
import io.micronaut.runtime.event.annotation.EventListener

@Singleton
class SampleEventListener {
    var invocationCounter = 0

    @EventListener
    internal fun onSampleEvent(event: SampleEvent) {
        invocationCounter++
    }

    @EventListener
    internal fun onStartupEvent(event: StartupEvent) {
        // startup logic here
    }

    @EventListener
    internal fun onShutdownEvent(event: ShutdownEvent) {
        // shutdown logic here
    }
}

如果您的偵聽器執(zhí)行的工作可能需要一段時間，請使用 @Async 注釋在單獨的線程上運行該操作：

使用@EventListener 異步監(jiān)聽事件

Java Groovy Kotlin

import io.micronaut.docs.context.events.SampleEvent;
import io.micronaut.runtime.event.annotation.EventListener;
import io.micronaut.scheduling.annotation.Async;

@Singleton
public class SampleEventListener {
    private AtomicInteger invocationCounter = new AtomicInteger(0);

    @EventListener
    @Async
    public void onSampleEvent(SampleEvent event) {
        invocationCounter.getAndIncrement();
    }

    public int getInvocationCounter() {
        return invocationCounter.get();
    }
}

import io.micronaut.context.ApplicationContext;
import io.micronaut.docs.context.events.SampleEventEmitterBean;
import org.junit.Test;

import static java.util.concurrent.TimeUnit.SECONDS;
import static org.awaitility.Awaitility.await;
import static org.hamcrest.Matchers.equalTo;
import static org.junit.Assert.assertEquals;

public class SampleEventListenerSpec {

    @Test
    public void testEventListenerIsNotified() {
        try (ApplicationContext context = ApplicationContext.run()) {
            SampleEventEmitterBean emitter = context.getBean(SampleEventEmitterBean.class);
            SampleEventListener listener = context.getBean(SampleEventListener.class);
            assertEquals(0, listener.getInvocationCounter());
            emitter.publishSampleEvent();
            await().atMost(5, SECONDS).until(listener::getInvocationCounter, equalTo(1));
        }
    }
}

import io.micronaut.docs.context.events.SampleEvent
import io.micronaut.runtime.event.annotation.EventListener
import io.micronaut.scheduling.annotation.Async

@Singleton
class SampleEventListener {
    AtomicInteger invocationCounter = new AtomicInteger(0)

    @EventListener
    @Async
    void onSampleEvent(SampleEvent event) {
        invocationCounter.getAndIncrement()
    }
}

import io.micronaut.context.ApplicationContext
import io.micronaut.docs.context.events.SampleEventEmitterBean
import spock.lang.Specification
import spock.util.concurrent.PollingConditions

class SampleEventListenerSpec extends Specification {

    void "test event listener is notified"() {
        given:
        def context = ApplicationContext.run()
        def emitter = context.getBean(SampleEventEmitterBean)
        def listener = context.getBean(SampleEventListener)

        expect:
        listener.invocationCounter.get() == 0

        when:
        emitter.publishSampleEvent()

        then:
        new PollingConditions(timeout: 5).eventually {
            listener.invocationCounter.get() == 1
        }

        cleanup:
        context.close()
    }
}

import io.micronaut.docs.context.events.SampleEvent
import io.micronaut.runtime.event.annotation.EventListener
import io.micronaut.scheduling.annotation.Async
import java.util.concurrent.atomic.AtomicInteger

@Singleton
open class SampleEventListener {

    var invocationCounter = AtomicInteger(0)

    @EventListener
    @Async
    open fun onSampleEvent(event: SampleEvent) {
        println("Incrementing invocation counter...")
        invocationCounter.getAndIncrement()
    }
}

import io.kotest.assertions.timing.eventually
import io.kotest.matchers.shouldBe
import io.kotest.core.spec.style.AnnotationSpec
import io.micronaut.context.ApplicationContext
import io.micronaut.docs.context.events.SampleEventEmitterBean
import org.opentest4j.AssertionFailedError
import kotlin.time.DurationUnit
import kotlin.time.ExperimentalTime
import kotlin.time.toDuration

@ExperimentalTime
class SampleEventListenerSpec : AnnotationSpec() {

    @Test
    suspend fun testEventListenerWasNotified() {
        val context = ApplicationContext.run()
        val emitter = context.getBean(SampleEventEmitterBean::class.java)
        val listener = context.getBean(SampleEventListener::class.java)
        listener.invocationCounter.get().shouldBe(0)
        emitter.publishSampleEvent()

        eventually(5.toDuration(DurationUnit.SECONDS), AssertionFailedError::class) {
            println("Current value of counter: " + listener.invocationCounter.get())
            listener.invocationCounter.get().shouldBe(1)
        }

        context.close()
    }
}

默認(rèn)情況下，事件偵聽器在計劃的執(zhí)行程序上運行。您可以根據(jù)需要在配置文件（例如 application.yml）中配置此線程池：

配置定時任務(wù)線程池

Properties Yaml Toml Groovy Hocon JSON

micronaut.executors.scheduled.type=scheduled
micronaut.executors.scheduled.core-pool-size=30

micronaut:
  executors:
    scheduled:
      type: scheduled
      core-pool-size: 30

[micronaut]
  [micronaut.executors]
    [micronaut.executors.scheduled]
      type="scheduled"
      core-pool-size=30

micronaut {
  executors {
    scheduled {
      type = "scheduled"
      corePoolSize = 30
    }
  }
}

{
  micronaut {
    executors {
      scheduled {
        type = "scheduled"
        core-pool-size = 30
      }
    }
  }
}

{
  "micronaut": {
    "executors": {
      "scheduled": {
        "type": "scheduled",
        "core-pool-size": 30
      }
    }
  }
}

以上內(nèi)容是否對您有幫助：

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