最近在做公司的業(yè)務需要用到事件通知，比如啟動成功打印日志，通知其他業(yè)務做相應的操作，就用到了Spring的事件通知機制。

1. Spring的事件通知

Spring的事件通知本質(zhì)上就是發(fā)布-訂閱，即生產(chǎn)者-消費者；體現(xiàn)了觀察者設計模式或者回調(diào)通知，那么Spring的事件是如何使用的？

有3要素：發(fā)布者-->事件-->監(jiān)聽者

2. Spring事件通知使用

Spring的事件必須依賴Spring容器，所以我在寫demo的時候，需要Spring-boot-starter。

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <version>2.1.1.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.4</version>
        </dependency>
    </dependencies>

2.1 Spring的事件

Spring的事件定義在ApplicationEvent類中，我們可以根據(jù)自己的需要自定義事件實體javabean。

@Data
public class TestSpringEvent extends ApplicationEvent {
    /**
     * Create a new ApplicationEvent.
     *
     * @param source the object on which the event initially occurred (never {@code null})
     */
    public TestSpringEvent(Object source) {
        super(source);
    }
 
    private Integer code;
    private String message;
 
}

跟蹤源碼：

public abstract class ApplicationEvent extends EventObject {
 
	/** use serialVersionUID from Spring 1.2 for interoperability. */
	private static final long serialVersionUID = 7099057708183571937L;
 
	/** System time when the event happened. */
	private final long timestamp; 
 
	/**
	 * Create a new ApplicationEvent.
	 * @param source the object on which the event initially occurred (never {@code null})
	 */
	public ApplicationEvent(Object source) {
		super(source);
		this.timestamp = System.currentTimeMillis();
	}
 
 
	/**
	 * Return the system time in milliseconds when the event happened.
	 */
	public final long getTimestamp() {
		return this.timestamp;
	} 
}

可以看出ApplicationEvent有屬性時間戳，即事件的產(chǎn)生的時間，并有Object source屬性，這個source是有特定意義的，官方的doc是The object on which the Event initially occurred.即發(fā)布事件的實體類。

進一步跟蹤

public class EventObject implements java.io.Serializable { 
    private static final long serialVersionUID = 5516075349620653480L; 
    /**
     * The object on which the Event initially occurred.
     */
    protected transient Object  source;
 
    /**
     * Constructs a prototypical Event.
     *
     * @param    source    The object on which the Event initially occurred.
     * @exception  IllegalArgumentException  if source is null.
     */
    public EventObject(Object source) {
        if (source == null)
            throw new IllegalArgumentException("null source");
 
        this.source = source;
    }
 
    /**
     * The object on which the Event initially occurred.
     *
     * @return   The object on which the Event initially occurred.
     */
    public Object getSource() {
        return source;
    }
 
    /**
     * Returns a String representation of this EventObject.
     *
     * @return  A a String representation of this EventObject.
     */
    public String toString() {
        return getClass().getName() + "[source=" + source + "]";
    }
}

定義了一個事件發(fā)生的不能序列化的對象

2.2 事件監(jiān)聽

2.2.1 接口方式實現(xiàn)

Spring事件的監(jiān)聽由ApplicationListener定義，我們寫2個，來測試監(jiān)聽它執(zhí)行的順序

@Component
public class TestApplicationListener implements ApplicationListener<TestSpringEvent> { 
    //@Async
    public void onApplicationEvent(TestSpringEvent event) {
        System.out.println("code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage());
    }
}
 
@Component
public class TestApplicationListenerCopy implements ApplicationListener<TestSpringEvent> { 
    //@Async
    public void onApplicationEvent(TestSpringEvent event) {
        System.out.println("2：code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage());
    }
}

跟蹤代碼，可以看出ApplicationListener是一個函數(shù)式接口

@FunctionalInterface
public interface ApplicationListener<E extends ApplicationEvent> extends EventListener { 
	/**
	 * Handle an application event.
	 * @param event the event to respond to
	 */
	void onApplicationEvent(E event); 
}

Spring事件監(jiān)聽器的默認是單線程同步執(zhí)行，異步執(zhí)行需要加上Spring的@Async注解，或者自定義線程池實現(xiàn).

2.2.2 注解實現(xiàn)

也可以使用@EventListener

package com.feng.spring.listener; 
import com.feng.spring.event.TestSpringEvent;
import org.springframework.context.event.EventListener;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;
 
@Component
public class TestApplicationListener2{
 
    //@Async
    @EventListener
    public void onApplicationEvent(TestSpringEvent event) {
        System.out.println("step2：code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage());
    }
}
 
@Component
public class TestApplicationListener2Copy {
 
    //@Async
    @EventListener
    public void onApplicationEvent(TestSpringEvent event) {
        System.out.println("step3:code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage());
    }
}

同理寫2個實現(xiàn)

2.3 事件發(fā)布

Spring的事件的發(fā)布定義在ApplicationEventPublisher類中，而ApplicationContext繼承了這個類，因此ApplicationContext具有發(fā)布事件的能力，而且已經(jīng)注入Spring的bean容器中，可直接獲取。

public class SpringEventMain {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
        context.scan(SpringEventMain.class.getCanonicalName());
        context.refresh();
 
        TestSpringEvent testSpringEvent = new TestSpringEvent(new SpringEventMain());
        testSpringEvent.setCode(10000);
        testSpringEvent.setMessage("---------My Spring task event------------");
        context.publishEvent(testSpringEvent);
    }
}

注意：

new TestSpringEvent(new SpringEventMain())

這里的source是傳入發(fā)布事件的實例對象。

運行后打印如下日志：

/software/jdk1.8.0_191/bin/java -javaagent:/software/ideaIde/lib/idea_rt.jar=36631:/software/ideaIde/bin -Dfile.encoding=UTF-8 -classpath /software/jdk1.8.0_191/jre/lib/charsets.jar:/software/jdk1.8.0_191/jre/lib/deploy.jar:/software/jdk1.8.0_191/jre/lib/ext/cldrdata.jar:/software/jdk1.8.0_191/jre/lib/ext/dnsns.jar:/software/jdk1.8.0_191/jre/lib/ext/jaccess.jar:/software/jdk1.8.0_191/jre/lib/ext/jfxrt.jar:/software/jdk1.8.0_191/jre/lib/ext/localedata.jar:/software/jdk1.8.0_191/jre/lib/ext/nashorn.jar:/software/jdk1.8.0_191/jre/lib/ext/sunec.jar:/software/jdk1.8.0_191/jre/lib/ext/sunjce_provider.jar:/software/jdk1.8.0_191/jre/lib/ext/sunpkcs11.jar:/software/jdk1.8.0_191/jre/lib/ext/zipfs.jar:/software/jdk1.8.0_191/jre/lib/javaws.jar:/software/jdk1.8.0_191/jre/lib/jce.jar:/software/jdk1.8.0_191/jre/lib/jfr.jar:/software/jdk1.8.0_191/jre/lib/jfxswt.jar:/software/jdk1.8.0_191/jre/lib/jsse.jar:/software/jdk1.8.0_191/jre/lib/management-agent.jar:/software/jdk1.8.0_191/jre/lib/plugin.jar:/software/jdk1.8.0_191/jre/lib/resources.jar:/software/jdk1.8.0_191/jre/lib/rt.jar:/home/huahua/IdeaProjects/feng/spring-event/target/classes:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-starter/2.1.1.RELEASE/spring-boot-starter-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot/2.1.1.RELEASE/spring-boot-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-context/5.1.3.RELEASE/spring-context-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-aop/5.1.3.RELEASE/spring-aop-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-beans/5.1.3.RELEASE/spring-beans-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-expression/5.1.3.RELEASE/spring-expression-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.1.1.RELEASE/spring-boot-autoconfigure-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.1.1.RELEASE/spring-boot-starter-logging-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar:/home/huahua/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar:/home/huahua/.m2/repository/org/slf4j/slf4j-api/1.7.25/slf4j-api-1.7.25.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.11.1/log4j-to-slf4j-2.11.1.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-api/2.11.1/log4j-api-2.11.1.jar:/home/huahua/.m2/repository/org/slf4j/jul-to-slf4j/1.7.25/jul-to-slf4j-1.7.25.jar:/home/huahua/.m2/repository/javax/annotation/javax.annotation-api/1.3.2/javax.annotation-api-1.3.2.jar:/home/huahua/.m2/repository/org/springframework/spring-core/5.1.3.RELEASE/spring-core-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-jcl/5.1.3.RELEASE/spring-jcl-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/yaml/snakeyaml/1.23/snakeyaml-1.23.jar:/home/huahua/.m2/repository/org/projectlombok/lombok/1.18.4/lombok-1.18.4.jar com.feng.spring.SpringEventMain
17:54:05.347 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [/home/huahua/IdeaProjects/feng/spring-event/target/classes/com/feng/spring/listener/TestApplicationListener.class]
17:54:05.352 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [/home/huahua/IdeaProjects/feng/spring-event/target/classes/com/feng/spring/listener/TestApplicationListener2.class]
17:54:05.353 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [/home/huahua/IdeaProjects/feng/spring-event/target/classes/com/feng/spring/listener/TestApplicationListener3.class]
17:54:05.353 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [/home/huahua/IdeaProjects/feng/spring-event/target/classes/com/feng/spring/listener/TestApplicationListenerCopy.class]
17:54:05.358 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@64b8f8f4
17:54:05.380 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
17:54:05.438 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
17:54:05.440 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
17:54:05.443 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
17:54:05.444 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalCommonAnnotationProcessor'
17:54:05.451 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'testApplicationListener'
17:54:05.466 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'testApplicationListener2'
17:54:05.470 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'testApplicationListener3'
17:54:05.471 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'testApplicationListenerCopy'
17:54:05.490 [main] DEBUG org.springframework.context.event.EventListenerMethodProcessor - 1 @EventListener methods processed on bean 'testApplicationListener2': {public void com.feng.spring.listener.TestApplicationListener2.onApplicationEvent(com.feng.spring.event.TestSpringEvent)=@org.springframework.context.event.EventListener(condition=, value=[], classes=[])}
17:54:05.491 [main] DEBUG org.springframework.context.event.EventListenerMethodProcessor - 1 @EventListener methods processed on bean 'testApplicationListener3': {public void com.feng.spring.listener.TestApplicationListener3.onApplicationEvent(com.feng.spring.event.TestSpringEvent)=@org.springframework.context.event.EventListener(condition=, value=[], classes=[])}
step2:code is: 10000, message is: ---------My Spring task event------------
step3:code is: 10000, message is: ---------My Spring task event------------
code is: 10000, message is: ---------My Spring task event------------
2：code is: 10000, message is: ---------My Spring task event------------

Process finished with exit code 0

說明Spring事件發(fā)布訂閱成功。同時使用注解的監(jiān)聽比實現(xiàn)類監(jiān)聽先監(jiān)聽，如果我們需要監(jiān)聽的執(zhí)行順序怎么辦？比如某些監(jiān)聽器先執(zhí)行？

2.4 Spring順序監(jiān)聽器

上面的示例，其實都是注解或者都是實現(xiàn)類，監(jiān)聽器是沒有順序的。如果我們要實現(xiàn)順序監(jiān)聽呢？我么需要Ordered接口的實現(xiàn)，Spring提供的實現(xiàn)或者暴露的實現(xiàn)接口如下

如果需要執(zhí)行順序，Spring提供SmartApplicationListener與GenericApplicationListener可供選擇。

其中GenericApplicationListener，Spring官方推薦我們提供adapter實現(xiàn)

/**
 * Extended variant of the standard {@link ApplicationListener} interface,
 * exposing further metadata such as the supported event and source type.
 *
 * <p>As of Spring Framework 4.2, this interface supersedes the Class-based
 * {@link SmartApplicationListener} with full handling of generic event types.
 *
 * @author Stephane Nicoll
 * @since 4.2
 * @see SmartApplicationListener
 * @see GenericApplicationListenerAdapter
 */

/**
 * Extended variant of the standard {@link ApplicationListener} interface,
 * exposing further metadata such as the supported event and source type.
 *
 * <p>As of Spring Framework 4.2, this interface supersedes the Class-based
 * {@link SmartApplicationListener} with full handling of generic event types.
 *
 * @author Stephane Nicoll
 * @since 4.2
 * @see SmartApplicationListener
 * @see GenericApplicationListenerAdapter
 */
public interface GenericApplicationListener extends ApplicationListener<ApplicationEvent>, Ordered {
 
	/**
	 * Determine whether this listener actually supports the given event type.
	 * @param eventType the event type (never {@code null})
	 */
	boolean supportsEventType(ResolvableType eventType);
 
	/**
	 * Determine whether this listener actually supports the given source type.
	 * <p>The default implementation always returns {@code true}.
	 * @param sourceType the source type, or {@code null} if no source
	 */
	default boolean supportsSourceType(@Nullable Class<?> sourceType) {
		return true;
	}
 
	/**
	 * Determine this listener's order in a set of listeners for the same event.
	 * <p>The default implementation returns {@link #LOWEST_PRECEDENCE}.
	 */
	@Override
	default int getOrder() {
		return LOWEST_PRECEDENCE;
	} 
}

其實ApplicationListener在Spring中提供了很多默認實現(xiàn)，其中就有SmartApplicationListener，智能監(jiān)聽器。

下面來試試

 */
public interface SmartApplicationListener extends ApplicationListener<ApplicationEvent>, Ordered {
 
	/**
	 * Determine whether this listener actually supports the given event type.
	 * @param eventType the event type (never {@code null})
	 */
      //supportsEventType與supportsSourceType同時true，監(jiān)聽器才會執(zhí)行
      //監(jiān)聽器支持的事件類型
	boolean supportsEventType(Class<? extends ApplicationEvent> eventType);
 
	/**
	 * Determine whether this listener actually supports the given source type.
	 * <p>The default implementation always returns {@code true}.
	 * @param sourceType the source type, or {@code null} if no source
	 */
      //supportsEventType與supportsSourceType同時true，監(jiān)聽器才會執(zhí)行
      //監(jiān)聽事件發(fā)布的類
	default boolean supportsSourceType(@Nullable Class<?> sourceType) {
		return true;
	}
 
	/**
	 * Determine this listener's order in a set of listeners for the same event.
	 * <p>The default implementation returns {@link #LOWEST_PRECEDENCE}.
	 */
	@Override
	default int getOrder() {
		return LOWEST_PRECEDENCE;
	} 
}

3個實現(xiàn)方法。支持的類型，支持的事件類，執(zhí)行順序

package com.feng.spring.listener; 
import com.feng.spring.SpringEventMain;
import com.feng.spring.event.TestSpringEvent;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.event.SmartApplicationListener;
import org.springframework.stereotype.Component;
 
@Component
public class OrderedListener implements SmartApplicationListener {
    public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
        return eventType== TestSpringEvent.class;
    }
 
    public boolean supportsSourceType(Class<?> sourceType) {
        return SpringEventMain.class==sourceType;
    }
 
    public int getOrder() {
        return 5;
    }
 
    public void onApplicationEvent(ApplicationEvent event) {
        System.out.println("my execute step is 555555555555555555555555555");
    }
} 
 
@Component
public class OrderedListenerCopy implements SmartApplicationListener {
    public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
        return eventType== TestSpringEvent.class;
    }
 
    public boolean supportsSourceType(Class<?> sourceType) {
        return SpringEventMain.class==sourceType;
    }
 
    public int getOrder() {
        return 6;
    }
 
    public void onApplicationEvent(ApplicationEvent event) {
        System.out.println("my execute step is 6666666666666666666666666666");
    }
}

同理寫2個，執(zhí)行結(jié)果如下：

/software/jdk1.8.0_191/bin/java -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:46603,suspend=y,server=n -javaagent:/software/ideaIde/lib/rt/debugger-agent.jar -Dfile.encoding=UTF-8 -classpath /software/jdk1.8.0_191/jre/lib/charsets.jar:/software/jdk1.8.0_191/jre/lib/deploy.jar:/software/jdk1.8.0_191/jre/lib/ext/cldrdata.jar:/software/jdk1.8.0_191/jre/lib/ext/dnsns.jar:/software/jdk1.8.0_191/jre/lib/ext/jaccess.jar:/software/jdk1.8.0_191/jre/lib/ext/jfxrt.jar:/software/jdk1.8.0_191/jre/lib/ext/localedata.jar:/software/jdk1.8.0_191/jre/lib/ext/nashorn.jar:/software/jdk1.8.0_191/jre/lib/ext/sunec.jar:/software/jdk1.8.0_191/jre/lib/ext/sunjce_provider.jar:/software/jdk1.8.0_191/jre/lib/ext/sunpkcs11.jar:/software/jdk1.8.0_191/jre/lib/ext/zipfs.jar:/software/jdk1.8.0_191/jre/lib/javaws.jar:/software/jdk1.8.0_191/jre/lib/jce.jar:/software/jdk1.8.0_191/jre/lib/jfr.jar:/software/jdk1.8.0_191/jre/lib/jfxswt.jar:/software/jdk1.8.0_191/jre/lib/jsse.jar:/software/jdk1.8.0_191/jre/lib/management-agent.jar:/software/jdk1.8.0_191/jre/lib/plugin.jar:/software/jdk1.8.0_191/jre/lib/resources.jar:/software/jdk1.8.0_191/jre/lib/rt.jar:/home/huahua/IdeaProjects/feng/spring-event/target/classes:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-starter/2.1.1.RELEASE/spring-boot-starter-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot/2.1.1.RELEASE/spring-boot-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-context/5.1.3.RELEASE/spring-context-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-aop/5.1.3.RELEASE/spring-aop-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-beans/5.1.3.RELEASE/spring-beans-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-expression/5.1.3.RELEASE/spring-expression-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.1.1.RELEASE/spring-boot-autoconfigure-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.1.1.RELEASE/spring-boot-starter-logging-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar:/home/huahua/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar:/home/huahua/.m2/repository/org/slf4j/slf4j-api/1.7.25/slf4j-api-1.7.25.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.11.1/log4j-to-slf4j-2.11.1.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-api/2.11.1/log4j-api-2.11.1.jar:/home/huahua/.m2/repository/org/slf4j/jul-to-slf4j/1.7.25/jul-to-slf4j-1.7.25.jar:/home/huahua/.m2/repository/javax/annotation/javax.annotation-api/1.3.2/javax.annotation-api-1.3.2.jar:/home/huahua/.m2/repository/org/springframework/spring-core/5.1.3.RELEASE/spring-core-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-jcl/5.1.3.RELEASE/spring-jcl-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/yaml/snakeyaml/1.23/snakeyaml-1.23.jar:/home/huahua/.m2/repository/org/projectlombok/lombok/1.18.4/lombok-1.18.4.jar:/software/ideaIde/lib/idea_rt.jar com.feng.spring.SpringEventMain
Connected to the target VM, address: '127.0.0.1:46603', transport: 'socket'
18:37:51.002 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [/home/huahua/IdeaProjects/feng/spring-event/target/classes/com/feng/spring/listener/OrderedListener.class]
18:37:51.009 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [/home/huahua/IdeaProjects/feng/spring-event/target/classes/com/feng/spring/listener/OrderedListenerCopy.class]
18:37:51.017 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@37d31475
18:37:51.055 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
18:37:51.129 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
18:37:51.132 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
18:37:51.135 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
18:37:51.136 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalCommonAnnotationProcessor'
18:37:51.145 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'orderedListener'
18:37:51.154 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'orderedListenerCopy'
my execute step is 555555555555555555555555555
my execute step is 6666666666666666666666666666
Disconnected from the target VM, address: '127.0.0.1:46603', transport: 'socket'

Process finished with exit code 0

實現(xiàn)了順序的監(jiān)聽。

2.5 異步監(jiān)聽

Spring使用ThreadPoolTaskExecutor來執(zhí)行異步任務，其實就是SchedulingTaskExecutor，使用@EnableAsync注解@Async注解實現(xiàn)異步監(jiān)聽事件的調(diào)用

我們來試試

package com.feng.spring.config; 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor; 
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;
 
@Configuration
public class AsyncConfig { 
    @Bean
    public Executor initExecutor(){
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        //定制線程名稱，還可以定制線程group
        executor.setThreadFactory(new ThreadFactory() {
            private final AtomicInteger threadNumber = new AtomicInteger(1);
            
            @Override
            public Thread newThread(Runnable r) {
                Thread t = new Thread(Thread.currentThread().getThreadGroup(), r,
                        "async-eventListener-" + threadNumber.getAndIncrement(),
                        0);
                return t;
            }
        });
        executor.setCorePoolSize(10);
        executor.setMaxPoolSize(20);
        executor.setKeepAliveSeconds(5);
        executor.setQueueCapacity(100);
//        executor.setRejectedExecutionHandler(null);
        return executor;
    }
}

@EnableAsync
@Component
public class TestApplicationListener implements ApplicationListener<TestSpringEvent> { 
    @Async
    public void onApplicationEvent(TestSpringEvent event) {
        System.out.println("code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage());
        //通過線程group/名稱區(qū)別
        System.out.println(Thread.currentThread().getThreadGroup()+ "/" +Thread.currentThread().getName());
    }
}

執(zhí)行結(jié)果：

/software/jdk1.8.0_191/bin/java -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:44287,suspend=y,server=n -javaagent:/software/ideaIde/lib/rt/debugger-agent.jar -Dfile.encoding=UTF-8 -classpath /software/jdk1.8.0_191/jre/lib/charsets.jar:/software/jdk1.8.0_191/jre/lib/deploy.jar:/software/jdk1.8.0_191/jre/lib/ext/cldrdata.jar:/software/jdk1.8.0_191/jre/lib/ext/dnsns.jar:/software/jdk1.8.0_191/jre/lib/ext/jaccess.jar:/software/jdk1.8.0_191/jre/lib/ext/jfxrt.jar:/software/jdk1.8.0_191/jre/lib/ext/localedata.jar:/software/jdk1.8.0_191/jre/lib/ext/nashorn.jar:/software/jdk1.8.0_191/jre/lib/ext/sunec.jar:/software/jdk1.8.0_191/jre/lib/ext/sunjce_provider.jar:/software/jdk1.8.0_191/jre/lib/ext/sunpkcs11.jar:/software/jdk1.8.0_191/jre/lib/ext/zipfs.jar:/software/jdk1.8.0_191/jre/lib/javaws.jar:/software/jdk1.8.0_191/jre/lib/jce.jar:/software/jdk1.8.0_191/jre/lib/jfr.jar:/software/jdk1.8.0_191/jre/lib/jfxswt.jar:/software/jdk1.8.0_191/jre/lib/jsse.jar:/software/jdk1.8.0_191/jre/lib/management-agent.jar:/software/jdk1.8.0_191/jre/lib/plugin.jar:/software/jdk1.8.0_191/jre/lib/resources.jar:/software/jdk1.8.0_191/jre/lib/rt.jar:/home/huahua/IdeaProjects/feng/spring-event/target/classes:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-starter/2.1.1.RELEASE/spring-boot-starter-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot/2.1.1.RELEASE/spring-boot-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-context/5.1.3.RELEASE/spring-context-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-aop/5.1.3.RELEASE/spring-aop-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-beans/5.1.3.RELEASE/spring-beans-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-expression/5.1.3.RELEASE/spring-expression-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.1.1.RELEASE/spring-boot-autoconfigure-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.1.1.RELEASE/spring-boot-starter-logging-2.1.1.RELEASE.jar:/home/huahua/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar:/home/huahua/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar:/home/huahua/.m2/repository/org/slf4j/slf4j-api/1.7.25/slf4j-api-1.7.25.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.11.1/log4j-to-slf4j-2.11.1.jar:/home/huahua/.m2/repository/org/apache/logging/log4j/log4j-api/2.11.1/log4j-api-2.11.1.jar:/home/huahua/.m2/repository/org/slf4j/jul-to-slf4j/1.7.25/jul-to-slf4j-1.7.25.jar:/home/huahua/.m2/repository/javax/annotation/javax.annotation-api/1.3.2/javax.annotation-api-1.3.2.jar:/home/huahua/.m2/repository/org/springframework/spring-core/5.1.3.RELEASE/spring-core-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/springframework/spring-jcl/5.1.3.RELEASE/spring-jcl-5.1.3.RELEASE.jar:/home/huahua/.m2/repository/org/yaml/snakeyaml/1.23/snakeyaml-1.23.jar:/home/huahua/.m2/repository/org/projectlombok/lombok/1.18.4/lombok-1.18.4.jar:/software/ideaIde/lib/idea_rt.jar com.feng.spring.SpringEventMain
Connected to the target VM, address: '127.0.0.1:44287', transport: 'socket'
19:08:24.692 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [/home/huahua/IdeaProjects/feng/spring-event/target/classes/com/feng/spring/config/AsyncConfig.class]
19:08:24.730 [main] DEBUG org.springframework.context.annotation.ClassPathBeanDefinitionScanner - Identified candidate component class: file [/home/huahua/IdeaProjects/feng/spring-event/target/classes/com/feng/spring/listener/TestApplicationListener.class]
19:08:24.741 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@37d31475
19:08:24.782 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
19:08:25.091 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
19:08:25.094 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
19:08:25.099 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
19:08:25.100 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalCommonAnnotationProcessor'
19:08:25.106 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAsyncAnnotationProcessor'
19:08:25.109 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.scheduling.annotation.ProxyAsyncConfiguration'
19:08:25.252 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'asyncConfig'
19:08:25.261 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'testApplicationListener'
19:08:25.299 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'initExecutor'
19:08:25.330 [main] INFO org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor - Initializing ExecutorService 'initExecutor'
code is: 10000, message is: ---------My Spring task event------------
java.lang.ThreadGroup[name=main,maxpri=10]/async-eventListener-1

看線程名稱，已經(jīng)異步執(zhí)行了

[name=main,maxpri=10]/async-eventListener-1 

3. 總結(jié)

Spring的事件通知demo已經(jīng)完成，如果需要詳細的Spring事件從發(fā)布到訂閱的過程，需要跟蹤Spring的ApplicationContext的publishEvent的過程，其實Spring的ApplicationContext的啟動的過程中也定義了很詳細的事件，使用intellij idea分析，如下：

Spring事件通知的本質(zhì)：生產(chǎn)者-消費者，體現(xiàn)了設計模式的觀察者模式。

以上為個人經(jīng)驗，希望能給大家一個參考，也希望大家多多支持腳本之家。