在一些业务场景中，当Serverlet容器初始化完成、重启、关闭等等一系列动作之后，需要处理一些操作，比如一些数据的加载、初始化缓存、特定任务的注册等等。这个时候我们就可以使用Spring提供的ApplicationListener来进行操作。
ApplicationEvent
|-ApplicationContextEvent
|-ContextClosedEvent：应用关闭事件
|-ContextRefreshedEvent：应用刷新事件
|-ContextStartedEvent：应用开启事件
|-ContextStoppedEvent：应用停止事件
本文以在Spring boot下的使用为例来进行说明。首先，需要实现ApplicationListener接口并实现onApplicationEvent方法。把需要处理的操作放在onApplicationEvent中进行处理：
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.context.embedded.EmbeddedServletContainerInitializedEvent;
import org.springframework.boot.context.event.ApplicationReadyEvent;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.context.event.ContextStartedEvent;
import org.springframework.context.event.ContextStoppedEvent;
/**
* Created by dongsilin on 2017/12/18.
*/
@Slf4j
public class AppApplicationListener implements ApplicationListener {
@Override
public void onApplicationEvent(ApplicationEvent event) {
log.info("+++++++++++++++++++++++++++++++++++++++++++++");
if (event instanceof ContextStartedEvent){
log.info("================:{}", "ContextStartedEvent");
}
if (event instanceof ContextRefreshedEvent){
log.info("================:{}", "ContextRefreshedEvent");
}
if (event instanceof ContextClosedEvent){
log.info("================:{}", "ContextClosedEvent");
}
if (event instanceof ContextStoppedEvent){
log.info("================:{}", "ContextStoppedEvent");
}
if (event instanceof EmbeddedServletContainerInitializedEvent){
log.info("================:{}", "EmbeddedServletContainerInitializedEvent");
}
if (event instanceof ApplicationReadyEvent){
log.info("================:{}", "ApplicationReadyEvent");
}
log.info(">>>>>>>>>>>>>>>>:{}\n", event.getClass().getName());
}
}
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
@Bean
public AppApplicationListener appApplicationListener(){
return new AppApplicationListener();
}
}
if(contextRefreshedEvent.getApplicationContext().getParent() != null){
return;
}
在spring中InitializingBean接口也提供了类似的功能，只不过它进行操作的时机是在所有bean都被实例化之后才进行调用。根据不同的业务场景和需求，可选择不同的方案来实现。
@Configuration
public class InitProperties implements ApplicationListener<ApplicationEnvironmentPreparedEvent> {
private static final Logger log = LoggerFactory.getLogger(InitProperties.class);
private static final String nacos_fat = "172.27.0.4:8848";
private static final String nacos_prod = "119.27.187.243:8848";
private static final String nacos_dev = "118.24.108.222:8848";
private static final String zipkin_fat = "http://118.24.108.222:9411";
private static final String zipkin_prod = "http://119.27.187.243:9411";
private static final Integer redis_min_idle = 0;
private static final Integer redis_max_idle = 8;
private static final Integer redis_max_active = 8;
private static final Integer redis_max_wait = 1000;
public InitProperties() {
}
public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {
ConfigurableEnvironment environment = event.getEnvironment();
String[] actives = environment.getActiveProfiles();
String active = "fat";
if (actives != null && actives.length > 0) {
active = actives[0];
}
Properties props = new Properties();
props.put("nacos.config.server-addr", "172.27.0.4:8848");
props.put("server.shutdown", "GRACEFUL");
props.put("management.endpoints.web.exposure.include", "*");
props.put("management.endpoint.health.show-details", "always");
props.put("spring.jackson.time-zone", "GMT+8");
props.put("spring.jackson.serialization.write-dates-as-timestamps", true);
props.put("spring.cloud.nacos.discovery.heart-beat-interval", 1);
props.put("spring.cloud.nacos.discovery.heart-beat-timeout", 1);
props.put("spring.cloud.nacos.discovery.ip-delete-timeout", 1);
if ("prod".equals(active)) {
props.put("spring.cloud.nacos.discovery.server-addr", "119.27.187.243:8848");
props.put("spring.cloud.nacos.discovery.namespace", "prod");
props.put("spring.zipkin.baseUrl", "http://119.27.187.243:9411");
props.put("swagger.production", true);
props.put("spring.redis.host", "10.0.0.2");
props.put("spring.redis.port", "6379");
props.put("spring.redis.password", "oLM0Bh!zn450");
props.put("spring.redis.lettuce.pool.max-active", redis_max_active);
props.put("spring.redis.lettuce.pool.max-idle", redis_max_idle);
props.put("spring.redis.lettuce.pool.max-wait", redis_max_wait);
props.put("spring.redis.lettuce.pool.min-idle", redis_min_idle);
log.info("===>配置 prod 环境默认参数");
} else if ("dev".equals(active)) {
props.put("nacos.config.server-addr", "139.155.27.221:8848");
props.put("spring.cloud.nacos.discovery.server-addr", "118.24.108.222:8848");
props.put("spring.cloud.nacos.discovery.namespace", "dev");
props.put("spring.redis.host", "118.24.108.222");
props.put("spring.redis.port", "6379");
props.put("spring.redis.password", "lgl250??");
props.put("spring.redis.lettuce.pool.max-active", redis_max_active);
props.put("spring.redis.lettuce.pool.max-idle", redis_max_idle);
props.put("spring.redis.lettuce.pool.max-wait", redis_max_wait);
props.put("spring.redis.lettuce.pool.min-idle", redis_min_idle);
props.put("spring.zipkin.baseUrl", "http://118.24.108.222:9411");
log.info("===>配置 dev 环境默认参数");
}
environment.getPropertySources().addFirst(new PropertiesPropertySource("nacos-config", props));
}
}
org.springframework.context.ApplicationListener = \
com.zto.business.baseconfig.properties.InitProperties
