Spring事件处理
你已经看到了所有的章节了Spring的核心是ApplicationContext，它管理bean的整个生命周期。ApplicationContext中加载bean时发布某些类型的事件。例如，一个ContextStartedEvent是当所述上下文被启动并发布，上下文被停止ContextStoppedEvent。
事件处理中ApplicationContext 通过了ApplicationEvent类和ApplicationListener接口提供。所以，如果一个bean实现了ApplicationListener，然后每anApplicationEvent被发布到ApplicationContext的时候通知bean。
Spring提供了以下标准的事件：
| S.N. | Spring 内置活动及说明 |
|---|---|
| 1 | ContextRefreshedEvent This event is published when the ApplicationContext is either initialized or refreshed. This can also be raised using the refresh() method on the ConfigurableApplicationContext interface. |
| 2 | ContextStartedEvent This event is published when the ApplicationContext is started using the start() method on theConfigurableApplicationContext interface. You can poll your database or you can re/start any stopped application after receiving this event. |
| 3 | ContextStoppedEvent This event is published when the ApplicationContext is stopped using the stop() method on the ConfigurableApplicationContext interface. You can do required housekeep work after receiving this event. |
| 4 | ContextClosedEvent This event is published when the ApplicationContext is closed using the close() method on theConfigurableApplicationContext interface. A closed context reaches its end of life; it cannot be refreshed or restarted. |
| 5 | RequestHandledEvent This is a web-specific event telling all beans that an HTTP request has been serviced. |
Spring事件处理是单线程的，所以如果一个事件被发布，直至及除非所有的接收器得到的消息，该进程被阻塞并且流程将不会继续。因此，应注意在设计应用程序时，如果事件处理被使用。
监听上下文事件：
要监听上下文事件，一个bean应该实现ApplicationListener接口，只有一个方法onApplicationEvent()。因此，让我们写一个例子，看看如何传播的事件，以及如何可以把代码来执行基于某些事件所需的任务。
让我们使用Eclipse IDE，然后按照下面的步骤来创建一个Spring应用程序：
| 步骤 | 描述 |
|---|---|
| 1 | Create a project with a name SpringExample and create a package com.yiibai under the src folder in the created project. |
| 2 | Add required Spring libraries using Add External JARs option as explained in the Spring Hello World Example chapter. |
| 3 | Create Java classes HelloWorld, CStartEventHandler, CStopEventHandler and MainAppunder the com.yiibai package. |
| 4 | Create Beans configuration file Beans.xml under the src folder. |
| 5 | The final step is to create the content of all the Java files and Bean Configuration file and run the application as explained below. |
这里是HelloWorld.java 文件的内容：
package com.yiibai; public class HelloWorld { private String message; public void setMessage(String message){ this.message = message; } public void getMessage(){ System.out.println("Your Message : " + message); } }
以下是CStartEventHandler.java文件的内容：
package com.yiibai; import org.springframework.context.ApplicationListener; import org.springframework.context.event.ContextStartedEvent; public class CStartEventHandler implements ApplicationListener<ContextStartedEvent>{ public void onApplicationEvent(ContextStartedEvent event) { System.out.println("ContextStartedEvent Received"); } }
以下是CStopEventHandler.java文件的内容：
package com.yiibai; import org.springframework.context.ApplicationListener; import org.springframework.context.event.ContextStoppedEvent; public class CStopEventHandler implements ApplicationListener<ContextStoppedEvent>{ public void onApplicationEvent(ContextStoppedEvent event) { System.out.println("ContextStoppedEvent Received"); } }
以下是MainApp.java文件的内容：
package com.yiibai; import org.springframework.context.ConfigurableApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp { public static void main(String[] args) { ConfigurableApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml"); // Let us raise a start event. context.start(); HelloWorld obj = (HelloWorld) context.getBean("helloWorld"); obj.getMessage(); // Let us raise a stop event. context.stop(); } }
以下是配置文件beans.xml文件：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="helloWorld" class="com.yiibai.HelloWorld"> <property name="message" value="Hello World!"/> </bean> <bean id="cStartEventHandler" class="com.yiibai.CStartEventHandler"/> <bean id="cStopEventHandler" class="com.yiibai.CStopEventHandler"/> </beans>
创建源程序和bean配置文件完成，让我们运行应用程序。如果一切顺利，这将打印以下信息：
ContextStartedEvent Received Your Message : Hello World! ContextStoppedEvent Received
如果喜欢，你可以发布自己的自定义事件，以后你可以捕捉相同处理那些自定义事件动作。如果你有兴趣在编写自己的自定义事件，可以查看 Spring自定义事件
正文到此结束
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文章和留言都翻到11页了 没有OOM
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朋友，翻页到11页，及以后，会出现OOM，无法访问
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搞个gitee的项目
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版本号是多少，你可以下载哪个代码仓库，jdk选1.8 直接跑就行
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