本例介绍SpringBoot的事件监听机制及使用
主要有ApplicationContextInitializer（上下文初始化器）、SpringApplicationRunListener（Spring应用运行监听器）、ApplicationRunner（启动加载类）、CommandLineRunner（启动加载类）
关于调用流程参考【SpringBoot】SpringBoot 启动原理（十五）
1、新建一个SpringBoot Web项目
1 <?xml version="1.0" encoding="UTF-8"?> 2 <project xmlns="http://maven.apache.org/POM/4.0.0" 3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 4 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> 5 <modelVersion>4.0.0</modelVersion> 6 7 <groupId>com.test</groupId> 8 <artifactId>test-springboot-runner</artifactId> 9 <version>1.0-SNAPSHOT</version>10 11 <parent>12 <groupId>org.springframework.boot</groupId>13 <artifactId>spring-boot-starter-parent</artifactId>14 <version>2.1.8.RELEASE</version>15 </parent>16 17 <properties>18 19 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>20 <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>21 <java.version>1.8</java.version>22 </properties>23 24 <dependencies>25 26 <dependency>27 <groupId>org.springframework.boot</groupId>28 <artifactId>spring-boot-starter-web</artifactId>29 </dependency>30 31 32 <dependency>33 <groupId>org.springframework.boot</groupId>34 <artifactId>spring-boot-starter-test</artifactId>35 <scope>test</scope>36 </dependency>37 38 </dependencies>39 40 41 <!-- SpringBoot打包插件，可以将代码打包成一个可执行的jar包 -->42 <build>43 <plugins>44 <plugin>45 <groupId>org.springframework.boot</groupId>46 <artifactId>spring-boot-maven-plugin</artifactId>47 </plugin>48 </plugins>49 </build>50 51 </project>View Code
2、新建HelloApplicationContextInitializer类，实现ApplicationContextInitializer接口，如下：
1 package com.test.springboot.listener; 2 3 import org.springframework.context.ApplicationContextInitializer; 4 import org.springframework.context.ConfigurableApplicationContext; 5 6 public class HelloApplicationContextInitializer implements ApplicationContextInitializer { 7 @Override 8 public void initialize(ConfigurableApplicationContext applicationContext) { 9 System.out.println("====HelloApplicationContextInitializer======initialize：" applicationContext);10 }11 }3、将HelloApplicationContextInitializer加入SpringBoot中，在resources目录下新建文件META-INF/spring.factories，添加一下内容
1 # Initializers2 org.springframework.context.ApplicationContextInitializer=3 com.test.springboot.listener.HelloApplicationContextInitializer
4、启动SpringBoot程序，查看控制台
1、在SpringBoot Web项目中，新建HelloSpringApplicationRunListener类，实现SpringApplicationRunListener接口
1 package com.test.springboot.listener; 2 3 import org.springframework.boot.SpringApplication; 4 import org.springframework.boot.SpringApplicationRunListener; 5 import org.springframework.context.ConfigurableApplicationContext; 6 import org.springframework.core.env.ConfigurableEnvironment; 7 8 public class HelloSpringApplicationRunListener implements SpringApplicationRunListener { 9 10 public HelloSpringApplicationRunListener(SpringApplication application, String[] args) {11 12 }13 14 @Override15 public void starting() {16 System.out.println("===HelloSpringApplicationRunListener===starting");17 }18 19 @Override20 public void environmentPrepared(ConfigurableEnvironment environment) {21 System.out.println("===os.name：" environment.getSystemProperties().get("os.name") );22 System.out.println("===HelloSpringApplicationRunListener===environmentPrepared");23 }24 25 @Override26 public void contextPrepared(ConfigurableApplicationContext context) {27 System.out.println("===HelloSpringApplicationRunListener===contextPrepared");28 }29 30 @Override31 public void contextLoaded(ConfigurableApplicationContext context) {32 System.out.println("===HelloSpringApplicationRunListener===contextLoaded");33 }34 35 @Override36 public void started(ConfigurableApplicationContext context) {37 System.out.println("===HelloSpringApplicationRunListener===started");38 }39 40 @Override41 public void running(ConfigurableApplicationContext context) {42 System.out.println("===HelloSpringApplicationRunListener===running");43 }44 45 @Override46 public void failed(ConfigurableApplicationContext context, Throwable exception) {47 System.out.println("===HelloSpringApplicationRunListener===failed");48 }49 }注意：HelloSpringApplicationRunListener必须添加构造方法，否则会包如下错误
HelloSpringApplicationRunListener的构造方法编写，可以参考SpringApplicationRunListener的其他实现类，如：EventPublishingRunListener
1 public class EventPublishingRunListener implements SpringApplicationRunListener, Ordered { 2 3 private final SpringApplication application; 4 5 private final String[] args; 6 7 private final SimpleApplicationEventMulticaster initialMulticaster; 8 9 public EventPublishingRunListener(SpringApplication application, String[] args) {10 this.application = application;11 this.args = args;12 this.initialMulticaster = new SimpleApplicationEventMulticaster();13 for (ApplicationListener<?> listener : application.getListeners()) {14 this.initialMulticaster.addApplicationListener(listener);15 }16 }17 18 ...19 20 }2、将HelloSpringApplicationRunListener加入SpringBoot中，在resources目录下新建文件META-INF/spring.factories，添加一下内容
1 # Run Listeners2 org.springframework.boot.SpringApplicationRunListener=3 com.test.springboot.listener.HelloSpringApplicationRunListener
3、测试启动SpringBoot程序，查看控制台
1、在SpringBoot Web项目中，新建HelloApplicationRunner类，实现接口 ApplicationRunner
1 @Component2 public class HelloApplicationRunner implements ApplicationRunner {3 @Override4 public void run(ApplicationArguments args) throws Exception {5 System.out.println("===HelloApplicationRunner===run");6 }7 }2、需要在HelloApplicationRunner类上加上注解@Component
3、启动SpringBoot项目，查看是否在启动时，调用了run方法
1、在SpringBoot Web项目中，新建HelloCommandLineRunner类，实现接口 CommandLineRunner
1 @Component2 public class HelloCommandLineRunner implements CommandLineRunner {3 @Override4 public void run(String... args) throws Exception {5 System.out.println("===HelloCommandLineRunner===run：" Arrays.asList(args));6 }7 }
2、需要在HelloCommandLineRunner类上加上注解@Component
3、启动SpringBoot项目，查看是否在启动时，调用了run方法
4、同时注入ApplicationRunner和CommandLineRunner，ApplicationRunner先回调，CommandLineRunner再回调
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