spring 事件驱动 以及线程分离

Spring事件模型事件驱动模型是一种观察者模式的典型应用，或者叫发布——订阅模型，Java中awt的事件机制和Spring的事件机制都是观察者模式的应用。一般都是发布者有更改变动时，订阅者会接收到发布者的变动通知。举个通用的例子网上看新闻，首先我们需要去订阅新闻，当有新的新闻时，网站会自动推送新闻给已经订阅过该新闻的用户

下面一个两个例子
第一个例子非线程分离

import org.springframework.context.ApplicationEvent;public class TestEvent extends ApplicationEvent {    private static final long serialVersionUID = 1L;    private String message;    public TestEvent(Object source) {        super(source);    }    public TestEvent(Object source,String message) {        super(source);        this.message=message;    }    public void print(String threadName){    System.out.println(threadName+"....."+this.message+"......");    }}

import org.springframework.context.ApplicationEvent;import org.springframework.context.ApplicationListener;public class TestListener implements ApplicationListener<ApplicationEvent>{    @Override    public void onApplicationEvent(ApplicationEvent event) {        if(event instanceof TestEvent){            TestEvent testevent=(TestEvent)event;            testevent.print(Thread.currentThread().getName());        }    }}

import org.springframework.beans.BeansException;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;import org.springframework.context.ApplicationEvent;public class AppUtil implements ApplicationContextAware {    private static ApplicationContext appContext;    @Override    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {        appContext = applicationContext;    }    public static Object getBean(String paramString) {        return appContext.getBean(paramString);    }    public static void sendEvent(ApplicationEvent event){        appContext.publishEvent(event);    }}

public static void main(String[] args) {        ApplicationContext ctx=new ClassPathXmlApplicationContext("spring-context2.xml");        AppUtil.sendEvent(new TestEvent("", "message!!!"));    }

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"    xsi:schemaLocation="http://www.springframework.org/schema/beans      http://www.springframework.org/schema/beans/spring-beans-4.0.xsd      http://www.springframework.org/schema/aop      http://www.springframework.org/schema/aop/spring-aop-4.0.xsd">    <bean id="appUtil" class="com.eroadsf.springdemo.applicationAware.AppUtil" />    <bean id="testListener" class="com.eroadsf.springdemo.applicationAware.TestListener"></bean></beans>

最后结果
main…..message!!!……

下面的例子增加一个事件监听器

public class TestListener1 implements ApplicationListener<ApplicationEvent>{    @Override    public void onApplicationEvent(ApplicationEvent event) {        if(event instanceof TestEvent){            TestEvent testevent=(TestEvent)event;            testevent.print(Thread.currentThread().getName());        }    }}

配置文件增加一个监听器

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"    xsi:schemaLocation="http://www.springframework.org/schema/beans      http://www.springframework.org/schema/beans/spring-beans-4.0.xsd      http://www.springframework.org/schema/aop      http://www.springframework.org/schema/aop/spring-aop-4.0.xsd">    <bean id="appUtil" class="com.eroadsf.springdemo.applicationAware.AppUtil" />    <bean id="testListener" class="com.eroadsf.springdemo.applicationAware.TestListener"></bean>    <bean id="testListener1" class="com.eroadsf.springdemo.applicationAware.TestListener1"></bean></beans>

结果都是由main线程输出

main.....message!!!......main.....message!!!......

假设这个场景是一个支付，2个监听器 一个是邮件发送一个是短信发送，并且在同一个事务中，如果短信发送出现异常可能连支付操作都回滚了。

所以spring采取了线程分离技术
我们将配置文件修改如下:

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"    xsi:schemaLocation="http://www.springframework.org/schema/beans      http://www.springframework.org/schema/beans/spring-beans-4.0.xsd      http://www.springframework.org/schema/aop      http://www.springframework.org/schema/aop/spring-aop-4.0.xsd">    <bean id="appUtil" class="com.eroadsf.springdemo.applicationAware.AppUtil" />    <bean id="testListener" class="com.eroadsf.springdemo.applicationAware.TestListener"></bean>    <bean id="testListener1" class="com.eroadsf.springdemo.applicationAware.TestListener1"></bean>    <!-- 测试Spring事件机制 异步发布事件 -->     <bean id="taskExecutor"        class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor">        <property name="corePoolSize" value="5"></property>    </bean>    <bean id="applicationEventMulticaster"        class="org.springframework.context.event.SimpleApplicationEventMulticaster">        <property name="taskExecutor" ref="taskExecutor"></property>    </bean> </beans>

最后的输出结果看到是两个不同的线程输出的而且不是main线程

taskExecutor-3.....message!!!......taskExecutor-4.....message!!!......

这是因为SimpleApplicationEventMulticaster里增加了线程池的处理一个监听开一个线程执行onApplicationEvent(event);

@Override    @SuppressWarnings({ "unchecked", "rawtypes" })    public void multicastEvent(final ApplicationEvent event) {        for (final ApplicationListener listener : getApplicationListeners(event)) {            Executor executor = getTaskExecutor();            if (executor != null) {                executor.execute(new Runnable() {                    @Override                    public void run() {                        listener.onApplicationEvent(event);                    }                });            }            else {                listener.onApplicationEvent(event);            }        }    }