常用监听器：
//contextListener可以监听数据库的连接，第三方组件的交互，还有静态文件加载等等
servletContextListener
HttpSessionListener
servletRequestListener

<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><groupId>top.ytheng</groupId><artifactId>springboot-demo</artifactId><version>0.0.1</version><packaging>jar</packaging><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.0.5.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-thymeleaf</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-devtools</artifactId><optional>true</optional><scope>true</scope></dependency></dependencies><build><!-- 打包的名称 --><finalName>myspringboot</finalName><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin><plugin><artifactId>maven-compiler-plugin</artifactId><configuration><source>1.8</source><target>1.8</target></configuration></plugin></plugins></build>
</project>

package top.ytheng.demo.listener;import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;/** 上下文监听器* * */
@WebListener
public class ContextListener implements ServletContextListener {@Overridepublic void contextInitialized(ServletContextEvent sce) {// TODO Auto-generated method stubSystem.out.println("======contextInitialized======");}@Overridepublic void contextDestroyed(ServletContextEvent sce) {// TODO Auto-generated method stubSystem.out.println("======contextDestroyed======");}}

package top.ytheng.demo.listener;import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.annotation.WebListener;@WebListener
public class RequestListener implements ServletRequestListener{@Overridepublic void requestDestroyed(ServletRequestEvent sre) {// TODO Auto-generated method stubSystem.out.println("======requestDestroyed======");}@Overridepublic void requestInitialized(ServletRequestEvent sre) {// TODO Auto-generated method stubSystem.out.println("======requestInitialized======");}}

package top.ytheng.demo.controller;import java.util.HashMap;
import java.util.Map;import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
@RequestMapping("/api/v2/listener")
public class ListenerController {@GetMapping("/test")public Object testListener() {Map<String, Object> map = new HashMap<>();map.put("username", "theng");map.put("password", "123456");System.out.println("listenerController");return map;}
}

package top.ytheng.demo;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.web.servlet.ServletComponentScan;@SpringBootApplication //等于下面3个
//@SpringBootConfiguration
//@EnableAutoConfiguration
//@ComponentScan
//拦截器用到
@ServletComponentScan
public class DemoApplication {public static void main(String[] args) {SpringApplication.run(DemoApplication.class, args);}}

http://localhost:8080/api/v2/listener/test