Spring的ApplicationEvent實現

原理:ApplicationContextAware接口提供了publishEvent方法,實現了Observe(觀察者)設計模式的傳播機制,實現了對bean的傳播。經過ApplicationContextAware咱們能夠把系統中全部ApplicationEvent傳播給系統中全部的ApplicationListener。spring

直接上代碼:設計模式

1.定義本身的監聽事件app

2.定義本身的監聽器(負責處理本身的監聽事件)函數

3.定義一個bean觸發監聽事件測試

4.測試this

 

package com.test.eventListener;

import org.springframework.context.ApplicationEvent;

/**
 * @author admin
 * @date 2018/5/17 17:37
 * 新建StudentAddEvent類,實現抽象類org.springframework.context.ApplicationEvent
 * StudentAddEvent類中須要實現本身的構造函數
 *  增長學生監聽事件
 */
public class StudentAddEvent extends ApplicationEvent {

    private static final long serialVersionUID = 20L;

    /**
     * 學生姓名
     */
    private String name;

    /**
     * @param source
     */
    public StudentAddEvent(Object source, String name) {
        super(source);
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

 

package com.test.eventListener;

import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;

/**
 * @author admin
 * @date 2018/5/17 17:41
 * 新建StudentAddListener類,實現接口org.springframework.context.ApplicationListener中的onApplicationEvent方法,
 * 在該方法中只處理StudentAddEvent類型的ApplicationEvent事件
 * 定義StudentAddListener監聽器
 */
@Component
public class StudentAddListener implements ApplicationListener {

    public void onApplicationEvent(ApplicationEvent event) {
        // 1.判斷是不是增長學生對象的事件
        if (!(event instanceof StudentAddEvent)) {
            return;
        }

        // 2.是增長學生事件的對象,進行邏輯處理,好比記日誌、積分等
        StudentAddEvent studentAddEvent = (StudentAddEvent) event;
        System.out.println("增長了學生:" + studentAddEvent.getName());
    }
}
package com.test.eventListener;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * @author admin
 * @date 2018/5/17 17:45
 * 定義StudentAddBean觸發StudentAddEvent事件
 * 新建StudentAddBean類,實現接口 org.springframework.context.ApplicationContextAware中的setApplicationContext方法,
 * 在構造bean的時候注入Spring的上下文對象,以便經過Spring上下文對象的publishEvent方法來觸發StudentAddEvent事件
 */
@Component
public class StudentAddBean implements ApplicationContextAware {
    /**
     * 定義Spring上下文對象
     */
    private ApplicationContext applicationContext = null;

    /*
     * (non-Javadoc)
     *
     * @see
     * org.springframework.context.ApplicationContextAware#setApplicationContext
     * (org.springframework.context.ApplicationContext)
     */
    public void setApplicationContext(ApplicationContext applicationContext)
            throws BeansException {
        this.applicationContext = applicationContext;

    }

    /**
     * 增長一個學生
     *
     * @param studentName
     */
    public void addStudent(String studentName) {
        // 1.構造一個增長學生的事件
        StudentAddEvent aStudentEvent = new StudentAddEvent(
                applicationContext, studentName);
        // 2.觸發增長學生事件
        applicationContext.publishEvent(aStudentEvent);
    }

}
package com.test.eventListener;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author admin
 * @date 2018/5/17 17:55
 * ApplicationContext在運行期會自動檢測到全部實現了ApplicationListener的bean對象,並將其做爲事件接收對象。
 * 當ApplicationContext的publishEvent方法被觸發時,每一個實現了ApplicationListener接口的bean都會收到ApplicationEvent對象,
 * 每一個ApplicationListener可根據事件類型只接收處理本身感興趣的事件,好比上面的StudentAddListener只接收StudentAddEvent事件。
 */
public class EventListenerTest {
    public static void main(String[] args) {
        String[] xmlConfig = new String[] { "spring/spring.xml" };
        // 使用ApplicationContext來初始化系統
        ApplicationContext context = new ClassPathXmlApplicationContext(xmlConfig);
        StudentAddBean studentBean = (StudentAddBean) context.getBean("studentAddBean");
        studentBean.addStudent("張三");
        studentBean.addStudent("李四");
    }
}
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