目录1. Spring的事件通知2. Spring事件通知使用2.1 Spring的事件2.2 事件监听2.2.1 接口方式实现2.2.2 注解实现2.3 事件发布2.4 Spring顺序监听器2.5 异步监听3. 总结
最近在做公司的业务需要用到事件通知，比如启动成功打印日志，通知其他业务做相应的操作，就用到了Spring的事件通知机制。
1. Spring的事件通知
Spring的事件通知本质上就是发布-订阅，即生产者-消费者；体现了观察者设计模式或者回调通知，那么Spring的事件是如何使用的？
有3要素：发布者–>事件–>监听者
2. Spring事件通知使用
Spring的事件必须依赖Spring容器，所以我在写demo的时候，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的事件定义在ApplicationEvent类中，我们可以根据自己的需要自定义事件实体javabean。
@Datapublic 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; }
跟踪源码：
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有属性时间戳，即事件的产生的时间，并有Object source属性，这个source是有特定意义的，官方的doc是The object on which the Event initially occurred.即发布事件的实体类。
进一步跟踪
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 + "]"; }}
定义了一个事件发生的不能序列化的对象
2.2 事件监听
2.2.1 接口方式实现
Spring事件的监听由ApplicationListener定义，我们写2个，来测试监听它执行的顺序
@Componentpublic class TestApplicationListener implements ApplicationListener<TestSpringEvent> { //@Async public void onApplicationEvent(TestSpringEvent event) { System.out.println("code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage()); }} @Componentpublic 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()); }}
跟踪代码，可以看出ApplicationListener是一个函数式接口
@FunctionalInterfacepublic interface ApplicationListener<E extends ApplicationEvent> extends EventListener { /** * Handle an application event. * @param event the event to respond to */void onApplicationEvent(E event); }
Spring事件监听器的默认是单线程同步执行，异步执行需要加上Spring的@Async注解，或者自定义线程池实现.
2.2.2 注解实现
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; @Componentpublic class TestApplicationListener2{ //@Async @EventListener public void onApplicationEvent(TestSpringEvent event) { System.out.println("step2：code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage()); }} @Componentpublic class TestApplicationListener2Copy { //@Async @EventListener public void onApplicationEvent(TestSpringEvent event) { System.out.println("step3:code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage()); }}
同理写2个实现
2.3 事件发布
Spring的事件的发布定义在ApplicationEventPublisher类中，而ApplicationContext继承了这个类，因此ApplicationContext具有发布事件的能力，而且已经注入Spring的bean容器中，可直接获取。
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())
这里的source是传入发布事件的实例对象。
运行后打印如下日志：
/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.SpringEventMain17:54:05.347 [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@64b8f8f417:54:05.380 [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
说明Spring事件发布订阅成功。同时使用注解的监听比实现类监听先监听，如果我们需要监听的执行顺序怎么办？比如某些监听器先执行？
2.4 Spring顺序监听器
上面的示例，其实都是注解或者都是实现类，监听器是没有顺序的。如果我们要实现顺序监听呢？我么需要Ordered接口的实现，Spring提供的实现或者暴露的实现接口如下
如果需要执行顺序，Spring提供SmartApplicationListener与GenericApplicationListener可供选择。
其中GenericApplicationListener，Spring官方推荐我们提供adapter实现
/** * 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}. */@Overridedefault int getOrder() {return LOWEST_PRECEDENCE;} }
其实ApplicationListener在Spring中提供了很多默认实现，其中就有SmartApplicationListener，智能监听器。
下面来试试
*/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与supportsSourceType同时true，监听器才会执行 //监听器支持的事件类型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与supportsSourceType同时true，监听器才会执行 //监听事件发布的类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}. */@Overridedefault int getOrder() {return LOWEST_PRECEDENCE;} }
3个实现方法。支持的类型，支持的事件类，执行顺序
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; @Componentpublic 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"); }} @Componentpublic 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"); }}
同理写2个，执行结果如下：
/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.SpringEventMainConnected 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@37d3147518:37:51.055 [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 555555555555555555555555555my execute step is 6666666666666666666666666666Disconnected from the target VM, address: ‘127.0.0.1:46603’, transport: ‘socket’Process finished with exit code 0
实现了顺序的监听。
2.5 异步监听
Spring使用ThreadPoolTaskExecutor来执行异步任务，其实就是SchedulingTaskExecutor，使用@EnableAsync注解@Async注解实现异步监听事件的调用
我们来试试
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; @Configurationpublic class AsyncConfig { @Bean public Executor initExecutor(){ ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); //定制线程名称，还可以定制线程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@Componentpublic class TestApplicationListener implements ApplicationListener<TestSpringEvent> { @Async public void onApplicationEvent(TestSpringEvent event) { System.out.println("code is:\t" + event.getCode() + ",\tmessage is:\t" + event.getMessage()); //通过线程group/名称区别 System.out.println(Thread.currentThread().getThreadGroup()+ "/" +Thread.currentThread().getName()); }}
执行结果：
/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.SpringEventMainConnected 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@37d3147519:08:24.782 [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
看线程名称，已经异步执行了
[name=main,maxpri=10]/async-eventListener-1
3. 总结
Spring的事件通知demo已经完成，如果需要详细的Spring事件从发布到订阅的过程，需要跟踪Spring的ApplicationContext的publishEvent的过程，其实Spring的ApplicationContext的启动的过程中也定义了很详细的事件，使用intellij idea分析，如下：
Spring事件通知的本质：生产者-消费者，体现了设计模式的观察者模式。
以上为个人经验，希望能给大家一个参考，也希望大家多多支持。
唯有斯人面上簌簌流下的，是点点无声无行的热泪。
