Spring Boot的事件和監聽
在Spring Boot的框架中，處理一些通用的Spring框架的事件（如ContextRefreshedEvent），在SpringApplication中也會發送一下其他的應用的事件，下面來聊聊這些事件的觸發時間和用法。
在程式的啟動中，會有以下的事件觸發【在2.0版本中所有的事件按執行的先後順序如下】
1、ApplicationStartingEvent：開始啟動，但在除了註冊監聽器和初始化程式之外的任何處理之前。
2、ApplicationEnvironmentPreparedEvent：spring boot 對應Enviroment已經準備完畢，但此時上下文context還沒有建立。
3、ApplicationPreparedEvent：spring boot上下文context建立完成，但此時spring中的bean是沒有完全載入完成的。
4、ApplicationStartedEvent：在上下文建立之後但在任何應用程式和命令列引數被呼叫之前傳送
5、ApplicationReadyEvent：所有都準備完成
6、ApplicationFailedEvent：spring boot啟動異常時執行事件
由於有一些事件會在ApplicationContext之前就建立了，所已不能使用@Bean來註冊事件。事件的註冊有以下兩種方法：
1、使用SpringApplication.addListeners(…)或者SpringApplicationBuilder.listeners(…)註冊
2、新增一個META-INF/spring.factories檔案，然後在了按照以下格式新增要註冊的事件：org.springframework.context.ApplicationListener=com.example.project.MyListener
下面來看事件DEMO程式碼
專案的整體結構：
1、MyApplicationEnvironmentPreparedEvent.java
public class MyApplicationEnvironmentPreparedEvent implements ApplicationListener<ApplicationEnvironmentPreparedEvent> {
private Logger LOGGER = LoggerFactory.getLogger(this.getClass());
@Override
public void onApplicationEvent(ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
LOGGER.info("ApplicationEnvironmentPreparedEvent...");
}
}
2、MyApplicationFailedEvent.java
public class MyApplicationFailedEvent implements ApplicationListener<ApplicationFailedEvent> {
private Logger LOGGER = LoggerFactory.getLogger(this.getClass());
@Override
public void onApplicationEvent(ApplicationFailedEvent applicationFailedEvent) {
LOGGER.info("ApplicationFailedEvent...");
}
}
3、MyApplicationPreparedEvent .java
public class MyApplicationPreparedEvent implements ApplicationListener<ApplicationPreparedEvent> {
private Logger LOGGER = LoggerFactory.getLogger(this.getClass());
@Override
public void onApplicationEvent(ApplicationPreparedEvent applicationPreparedEvent) {
LOGGER.info("ApplicationPreparedEvent...");
}
}
4、MyApplicationReadyEvent .java
public class MyApplicationReadyEvent implements ApplicationListener<ApplicationReadyEvent> {
private Logger LOGGER = LoggerFactory.getLogger(this.getClass());
@Override
public void onApplicationEvent(ApplicationReadyEvent applicationReadyEvent) {
LOGGER.info("ApplicationReadyEvent...");
}
}
5、MyApplicationStartedEvent .java
public class MyApplicationStartedEvent implements ApplicationListener<ApplicationStartedEvent> {
private Logger LOGGER = LoggerFactory.getLogger(this.getClass());
@Override
public void onApplicationEvent(ApplicationStartedEvent applicationStartedEvent) {
LOGGER.info("ApplicationStartedEvent...");
}
}
6、MyApplicationStartingEvent .java
public class MyApplicationStartingEvent implements ApplicationListener<ApplicationStartingEvent> {
private Logger LOGGER = LoggerFactory.getLogger(this.getClass());
@Override
public void onApplicationEvent(ApplicationStartingEvent applicationStartingEvent) {
LOGGER.info("ApplicationStartingEvent...");
}
}
7、StartUpRunner.java
@Component
public class StartUpRunner implements CommandLineRunner {
private Logger LOGGER = LoggerFactory.getLogger(this.getClass());
@Override
public void run(String... strings) throws Exception {
LOGGER.info("StartUPRunner ....");
}
}
//方法1：使用SpringApplication.addListeners(…),則其Application .java檔案為【此時不用spring.factories檔案】
7、Application .java
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication springBootApplication = new SpringApplication(Application.class);
springBootApplication.addListeners(new MyApplicationEnvironmentPreparedEvent());
springBootApplication.addListeners(new MyApplicationFailedEvent());
springBootApplication.addListeners(new MyApplicationPreparedEvent());
springBootApplication.addListeners(new MyApplicationReadyEvent());
springBootApplication.addListeners(new MyApplicationStartedEvent());
springBootApplication.addListeners(new MyApplicationStartingEvent());
springBootApplication.run(args);
}
}
方法2：新增一個META-INF/spring.factories檔案註冊
,則其Application .java檔案為
7、Application .java
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication springBootApplication = new SpringApplication(Application.class);
springBootApplication.run(args);
}
}
spring.factories檔案為：
org.springframework.context.ApplicationListener=com.example.demo.MyApplicationEnvironmentPreparedEvent\
,com.example.demo.MyApplicationFailedEvent\
,com.example.demo.MyApplicationPreparedEvent\
,com.example.demo.MyApplicationReadyEvent\
,com.example.demo.MyApplicationStartedEvent\
,com.example.demo.MyApplicationStartingEvent
執行後的結果為：
原始碼地址：https://github.com/cdy1263/SpringBootDemo/tree/master/Chapter_2_1