利用spring的ApplicationListener监听某一类事件的发生

1、ApplicationListener在使用过程中可以监听某一事件的发生，可以做出相应的处理，这个方式不常用，但是在特殊情况下面还是有用的。

2、导包pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.troy</groupId>
  <artifactId>springInit</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  <dependencies>
      <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>3.2.8.RELEASE</version>
    </dependency>
  </dependencies>
</project>

3、web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
  <display-name>springInit</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
      <servlet-name>springmvc</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <init-param>
          <param-name>contextConfigLocation</param-name>
          <param-value>classpath:spring/spring-mvc.xml</param-value>
      </init-param>
      <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
      <servlet-name>springmvc</servlet-name>
      <url-pattern>/</url-pattern>
  </servlet-mapping>
  <filter>
      <filter-name>encodingFilter</filter-name>
      <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
      <init-param>
          <param-name>encoding</param-name>
          <param-value>UTF-8</param-value>
      </init-param>
      <init-param>
          <param-name>forceEncoding</param-name>
          <param-value>true</param-value>
      </init-param>
  </filter>
  <filter-mapping>
      <filter-name>encodingFilter</filter-name>
      <url-pattern>/</url-pattern>
  </filter-mapping>
</web-app>

4、spring-mvc.xml配置

<?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:context="http://www.springframework.org/schema/context" 
    xmlns:jdbc="http://www.springframework.org/schema/jdbc"  
    xmlns:jee="http://www.springframework.org/schema/jee" 
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:aop="http://www.springframework.org/schema/aop" 
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:util="http://www.springframework.org/schema/util"
    xmlns:jpa="http://www.springframework.org/schema/data/jpa"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
        http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">

    <mvc:annotation-driven/>
    <context:component-scan base-package="com.troy"/>
    <bean class="com.troy.springInit.SpringListenerEvent"/>
    <bean class="com.troy.springInit.SpringListener"/>
    <bean id="initApplicationContext" class="com.troy.springInit.InitApplicationContext"/>
</beans>

5、<bean class="com.troy.springInit.SpringListener"/>在spring的作用是为了在bean加载完成过后进行初始化加载
　　这里可以参考：http://www.cnblogs.com/ll409546297/p/6903357.html

6、目录结构，因为我用初始化加载来实现某一个事件的监听，自己可以根据相应事件触发来实现

7、触发方式

　　1）第一步：因为事件触发需要用到ApplicationContext的publishEvent来触发事件，我这里没有ClassPathXmlApplicationContext的方式来加载配置文件，而是实现ApplicationContextAware这个接口来实现ApplicationContext的加载

public class InitApplicationContext implements ApplicationContextAware{
    
    public static ApplicationContext ac;
    
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {       
       this.ac = applicationContext;       
    }  
}

　　2）第二步编写事件：继承ApplicationEvent类会要求重写一个构造方法

public class InitEvent extends ApplicationEvent{

    public String data;

    public InitEvent(Object source) {       
        super(source);               
    }
    public InitEvent(Object source,String data) {       
        super(source);    
        this.data = data;
    }
    public String getData() {
        return data;
    }
    public void setData(String data) {
        this.data = data;
    }   
    
    //这里我是利用spring初始化来实现方法的加载
    public static void execute(){
        ApplicationContext ac = InitApplicationContext.ac;
        System.out.println("test==================test");
        InitEvent ie = new InitEvent("test", "test");
        ac.publishEvent(ie);
    }
    
}

　　3）通过初始化的方式来触发这个事件，这个可以通过其他方式，比如servlet等方式来触发

public class SpringListener implements ApplicationListener<ContextRefreshedEvent>{
    
    public void onApplicationEvent(ContextRefreshedEvent event) {
        System.out.println(event.getApplicationContext());
        //判断spring容器是否加载完成
        if (event.getApplicationContext().getParent() == null) {
            Init.init();
            InitEvent.execute();
        }
    }
}

　　4）上面的方式也可以触发事件，但是写出来比较繁琐。我们一般通过ApplicationListener接口来实现事件的监听，这样来触发事件的产生。通过ApplicationListener的泛型机制，来监听事件的发生，这里可以针对于时间做相对处理，实现对事件的监听

public class SpringListenerEvent implements ApplicationListener<InitEvent>{

    public void onApplicationEvent(InitEvent event) {
        System.out.println("事件处理==================事件处理");
        System.out.println(event.getData());        
    }
}

8、总体来说：ApplicationListener是对相应应用的监听，只是对于不同方式，通过不同方式来呈现！