深入理解SpringBoot之启动探究

最新推荐文章于 2025-02-04 09:57:59 发布

原创最新推荐文章于 2025-02-04 09:57:59 发布 · 176 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#SpringBoot

本文通过模拟饥饿通知做饭的场景，深入探讨了SpringBoot中事件触发机制与监听处理机制。从定义事件、创建事件源、发布事件到监听事件并处理，详细介绍了SpringBoot如何利用事件机制实现组件间的解耦与协作。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

下面这篇文章是介绍SpringBoot的启动过程，从JDK的awt事件处理机制：事件 -> 发布事件 -> 监听者 -> 事件处理，然后由JDK的事件机制转向Spring框架对其支持与延伸，分析Spring框架再启动过程中事件触发机制与监听处理机制，最后又转向SpringBoot，讲解的非常好，感兴趣的blog可以学习了解一下。

深入理解SpringBoot之启动探究

下面是我在SpringBoot中，由Spring的事件机制，模拟一个场景，当感到饥饿时，通知厨师做饭。

首先是SpringBoot项目的pom.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>monic</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>monic</name>
    <description>在这里我们模拟一个场景，当感到饥饿时，通知厨师做饭</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>
</project>

定义事件：

package com.example.monic;


import org.springframework.context.ApplicationEvent;

/**
 * 定义一个描述饥饿状态的事件
 */
public class HungryEvent extends ApplicationEvent {

    /**
     * Create a new ApplicationEvent.
     *
     * @param source the object on which the event initially occurred (never {@code null})
     */
    public HungryEvent(Object source) {
        super(source);
    }
}

定义Person:

package com.example.monic;

import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.stereotype.Component;

/**
 * Person类，如果属性hungry的值为0，则通知厨师做饭吃。
 */
@Slf4j
@Data
@Component
public class Person implements ApplicationEventPublisherAware {

    private int hungry;

    private String name;

    private ApplicationEventPublisher applicationEventPublisher;

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.applicationEventPublisher = applicationEventPublisher;
    }

    public void isNeedEat() {
        if(this.hungry == 0) {
            log.warn("太饿了，需要吃东西");
            new Thread(() -> this.applicationEventPublisher.publishEvent(new HungryEvent(this))).start();
            log.info("通知完毕");
        }
    }
}

定义厨师类：

package com.example.monic;

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;

/**
 * 厨师类用于对饥饿事件的监听...
 */
@Slf4j
@Component
public class Chef implements ApplicationListener<HungryEvent> {
    @Override
    public void onApplicationEvent(HungryEvent event) {
        if(event.getSource() instanceof Person) {
            Person person = (Person)event.getSource();
            log.info(person.getName() + "饿了,开始做饭");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            log.info("做饭完毕....开始吃吧");
        }
    }
}

Main方法：

package com.example.monic;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication
public class MonicApplication {


    public static void main(String[] args) {
        ConfigurableApplicationContext applicationContext = SpringApplication.run(MonicApplication.class, args);


        Person person = applicationContext.getBean(Person.class);
        person.setHungry(0);
        person.setName("Tom");
        person.isNeedEat();
    }

}

执行Main方法后，我们可以看到如下结果：

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.6.RELEASE)

2019-07-02 14:45:55.999  INFO 7392 --- [           main] com.example.monic.MonicApplication       : Starting MonicApplication on M7228-PC with PID 7392 (D:\IdeaProjects\springbootstudy\monic\target\classes started by Administrator in D:\IdeaProjects\springbootstudy\monic)
2019-07-02 14:45:56.015  INFO 7392 --- [           main] com.example.monic.MonicApplication       : No active profile set, falling back to default profiles: default
2019-07-02 14:45:57.294  INFO 7392 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2019-07-02 14:45:57.310  INFO 7392 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2019-07-02 14:45:57.310  INFO 7392 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.21]
2019-07-02 14:45:57.403  INFO 7392 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2019-07-02 14:45:57.403  INFO 7392 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1217 ms
2019-07-02 14:45:57.559  INFO 7392 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2019-07-02 14:45:57.700  INFO 7392 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-07-02 14:45:57.700  INFO 7392 --- [           main] com.example.monic.MonicApplication       : Started MonicApplication in 2.013 seconds (JVM running for 2.72)
2019-07-02 14:45:57.700  WARN 7392 --- [           main] com.example.monic.Person                 : 太饿了，需要吃东西
2019-07-02 14:45:57.700  INFO 7392 --- [           main] com.example.monic.Person                 : 通知完毕
2019-07-02 14:45:57.700  INFO 7392 --- [       Thread-7] com.example.monic.Chef                   : Tom饿了,开始做饭
2019-07-02 14:45:59.714  INFO 7392 --- [       Thread-7] com.example.monic.Chef                   : 做饭完毕....开始吃吧