springboot 初始化完成时执行方法，ApplicationListener

约定不等于承诺〃 2022-05-14 17:22 232阅读 0赞

**ApplicationListener调用过程详解：**

**实现接口ApplicationListener，并重写public void onApplicationEvent(ApplicationEvent event) \{｝可以在容器初始话的时候执行这个方法**，其中源码为：

/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
 package org.springframework.context;
 
 import java.util.EventListener;
 
 /**
 * Interface to be implemented by application event listeners.
 * Based on the standard {@code java.util.EventListener} interface
 * for the Observer design pattern.
 *
 * As of Spring 3.0, an ApplicationListener can generically declare the event type
 * that it is interested in. When registered with a Spring ApplicationContext, events
 * will be filtered accordingly, with the listener getting invoked for matching event
 * objects only.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @param <E> the specific ApplicationEvent subclass to listen to
 * @see org.springframework.context.event.ApplicationEventMulticaster
 */
 @FunctionalInterface
 public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {
 
 	/**
 	 * Handle an application event.
 	 * @param event the event to respond to
 	 */
 	void onApplicationEvent(E event);
 
 }

事件类型：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdqaWVjaGFvOTQ1_size_27_color_FFFFFF_t_70][]

1、ApplicationContextEvent

是spring内置事件的父抽象类，构造方法传入spring的context容器，同时也有获取spring的context容器的方法。

2、ContextRefreshedEvent

当spring容器初始化或刷新时，会触发此事件。此事件在开发中常用，用于在spring容器启动时，导入自定义的bean实例到spring容器中。

3、ContextStartedEvent

当spring启动时，或者说是context调用start()方法时，会触发此事件。

4、ContextStoppedEvent

当spring停止时，或者说context调用stop()方法时，会触发此事件。

5、ContextClosedEvent

当spring关闭时，或者说context调用close()方法时，会触发此事件。

实际项目中根据需求使用对应事件：

import org.springframework.context.ApplicationListener;
 import org.springframework.context.event.ContextRefreshedEvent;
 
 import com.jh.ta.scheduler.Scheduler;
 
 /**
 * 
 * Author:杨杰超 
 * Date:2018年10月28日 下午9:18:05 
 * Copyright (c) 2018, yangjiechao@dingtalk.com All Rights Reserved. 
 *
 */
 public class ApplicationStartup implements ApplicationListener<ContextRefreshedEvent> {
 
 @Override
 public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
 // 初始化完成后. 执行一次同步系统参数
 Scheduler scheduler = contextRefreshedEvent.getApplicationContext().getBean(Scheduler.class);
 scheduler.syncSysParam();
 }
 }

可以在ApplicationStartup中添加类注解@Component，让spring容器管理起来。

或者在springboot启动类中手动添加listeners

public static void main(String[] args) {
            SpringApplication app = new SpringApplication(App.class);
            app.addListeners(new ApplicationStartup());
            app.run(args);
        }

2种方式皆可，

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