JavaWeb三大组件——Listener

青旅半醒 2023-10-14 14:07 66阅读 0赞

**目录**

Listener

八个Web监听器

注册Listener

父pom文件

pom文件

使用注解方式

ServletListener

HelloServlet

启动类

通过RegistrationBean注册

ServletListener

HelloServlet

MyWebConfig

启动类

运行结果

监听器结合钉钉机器人实现报警机制

1、创建钉钉群

2、钉钉群添加机器人

3、添加依赖编辑

4、接入代码编辑

结果展示

--------------------

![d306bf51ba82498d9851c46db30cb027.png][]

## Listener ##

**作用**：监听某个事件的发生，状态的改变  
**内部机制**：接口回调

## 八个Web监听器 ##

<table style="width:594px;"> 
 <thead> 
  <tr> 
   <th style="width:271px;">接口名</th> 
   <th style="width:322px;">作用</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="width:271px;">ServletContextListener</td> 
   <td style="width:322px;">ServletContext对象的创建</td> 
  </tr> 
  <tr> 
   <td style="width:271px;">HttpSessionListener</td> 
   <td style="width:322px;">Session对象的创建</td> 
  </tr> 
  <tr> 
   <td style="width:271px;">ServletRequestListener</td> 
   <td style="width:322px;">Request对象的创建</td> 
  </tr> 
  <tr> 
   <td style="width:271px;">ServletContextAttributeListener</td> 
   <td style="width:322px;">ServletContext属性变化</td> 
  </tr> 
  <tr> 
   <td style="width:271px;">HttpSessionAttributeListener</td> 
   <td style="width:322px;">Session属性变化</td> 
  </tr> 
  <tr> 
   <td style="width:271px;">ServletRequestAttributeListener</td> 
   <td style="width:322px;">Request属性变化</td> 
  </tr> 
  <tr> 
   <td style="width:271px;">HttpSessionActivationListener</td> 
   <td style="width:322px;">Session钝化与活化</td> 
  </tr> 
  <tr> 
   <td style="width:271px;">HttpSessionBindingListener</td> 
   <td style="width:322px;">Session与对象的绑定</td> 
  </tr> 
 </tbody> 
</table>

## 注册Listener ##

![9ff01c1bd2fb4266bcaec4f44a54910d.png][]

### 父pom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 https://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>2.2.5.RELEASE</version>
            <relativePath/> 
        </parent>
        <groupId>com.chensir</groupId>
        <artifactId>springboot</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>springboot</name>
        <description>springboot</description>
        <properties>
            <java.version>8</java.version>
        </properties>
    
        <packaging>pom</packaging>
    
        <modules>
            <module>servlet</module>
        </modules>
    
        <dependencies>
            <dependency>
                <groupId>cn.hutool</groupId>
                <artifactId>hutool-all</artifactId>
                <version>5.8.3</version>
            </dependency>
    
    
    
    
    
    
    
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.18.22</version>
            </dependency>
    
            <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>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
    </project>

### pom文件 ###

### 使用注解方式 ###

使用注解 在启动类上必须加 **@ServletComponentScan注解，**若使用bean方式注册，则不需要

#### ServletListener ####

package com.chensir.javaWeb;
    
    import cn.hutool.core.date.StopWatch;
    import lombok.extern.slf4j.Slf4j;
    
    import javax.servlet.ServletRequestEvent;
    import javax.servlet.ServletRequestListener;
    import javax.servlet.annotation.WebListener;
    
    @WebListener
    @Slf4j
    public class ServletListener implements ServletRequestListener {
    
        // StopWatch存储一组任务耗时时间
        StopWatch stopWatch = null;
    
        @Override
        public void requestInitialized(ServletRequestEvent sre) {
            stopWatch = new StopWatch("监控");
            stopWatch.start();
            log.info("-------有人来了----------");
        }
    
        @Override
        public void requestDestroyed(ServletRequestEvent sre){
            stopWatch.stop();
            log.info("-------有人出来了,耗时：{}----------",stopWatch.getTotalTimeSeconds());
    
            // todo:如果超过多少时间，发信息给开发者
        }
    }

#### HelloServlet ####

package com.chensir.javaWeb;
    
    import cn.hutool.core.thread.ThreadUtil;
    import lombok.extern.slf4j.Slf4j;
    
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet(value = {"/hello"})
    @Slf4j
    public class HelloServlet extends HttpServlet {
    
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
            resp.setContentType("text/html;charset=utf-8");
            resp.getWriter().write("你好,宝宝");
    
            log.info("给航天员打招呼！");
    
            // 睡眠5s
            ThreadUtil.safeSleep(5000);
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
        }
    }

#### 启动类 ####

import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.web.servlet.ServletComponentScan;
    
    @SpringBootApplication
    @ServletComponentScan
    public class ServletApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(ServletApplication.class, args);
        }
    
    }

### 通过RegistrationBean注册 ###

#### ServletListener ####

requestInitialized方法：当ServletRequest对象被创建时，容器会调用这个方法

requestDestroyed方法：当ServletRequest对象被销毁时，容器会调用这个方法

![334533b5cfb443ebab426a6586173755.png][]

#### HelloServlet ####

![5a2850be67b544e18066cb74f689fce9.png][]

#### MyWebConfig ####

import com.chensir.javaWeb.HelloServlet;
    import com.chensir.javaWeb.ServletListener;
    import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
    import org.springframework.boot.web.servlet.ServletRegistrationBean;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @Configuration
    public class MyWebConfig {
    
        @Bean
        public ServletRegistrationBean servletRegistrationBean() {
            ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean();
            servletRegistrationBean.setServlet(new HelloServlet());
            servletRegistrationBean.addUrlMappings("/helloBaby");
            return servletRegistrationBean;
        }
    
        @Bean
        public ServletListenerRegistrationBean servletListenerRegistrationBean() {
            ServletListenerRegistrationBean bean = new ServletListenerRegistrationBean();
            bean.setListener(new ServletListener());
            // 启用
            bean.setEnabled(true);
            return bean;
        }
    }

#### 启动类 ####

![b35845ba8f6d4f0e8258c4678cbc7e79.png][]

### 运行结果 ###

![364af165a4114586a117036bcf90ea20.png][]

![dab128662a40422686cb4f90f28492c6.png][]

## 监听器结合钉钉机器人实现报警机制 ##

### 1、创建钉钉群 ###

### 2、钉钉群添加机器人 ###

![471bf346bfbc4b288531c19a779126aa.png][]

![9f4d3bfc1da44e80af114ae23fc5bdc4.png][]

![21b5ceccb96646d69e5dd3024b3b2a3c.png][]

![ed7515fe95aa4479b45bb463528ceb48.png][]

![64d6a6ca66d94f229a06f24303426d48.png][]

注意：安全设置中可自己设置，我这使用自定义关键词，关键词输入为“来自钉钉机器人”，那么在发送消息时需要包含此内容才能发送成功！

![ea5b4ff4f008440d8f37883edfa16bb8.png][]

点击查看文档：

![ed10ead8cc1b4230b7403cdf94232e6e.png][]

### 3、添加依赖![f76d09335c8a430c8450f571436d5067.png][] ###

<dependency>
        <groupId>com.aliyun</groupId>
        <artifactId>alibaba-dingtalk-service-sdk</artifactId>
        <version>2.0.0</version>
    </dependency>

### 4、接入代码![f63676becb494156a3eed33f428f87cd.png][] ###

###  ###

复制代码到ServletListener中：

import cn.hutool.core.date.StopWatch;
    import com.dingtalk.api.DefaultDingTalkClient;
    import com.dingtalk.api.DingTalkClient;
    import com.dingtalk.api.request.OapiRobotSendRequest;
    import com.dingtalk.api.response.OapiRobotSendResponse;
    import com.taobao.api.ApiException;
    import lombok.SneakyThrows;
    import lombok.extern.slf4j.Slf4j;
    
    import javax.servlet.ServletRequestEvent;
    import javax.servlet.ServletRequestListener;
    import javax.servlet.annotation.WebListener;
    import java.util.Arrays;
    
    //@WebListener
    @Slf4j
    public class ServletListener implements ServletRequestListener {
    
        // StopWatch存储一组任务耗时时间
        StopWatch stopWatch = null;
    
        @Override
        public void requestInitialized(ServletRequestEvent sre) {
            stopWatch = new StopWatch("监控");
            stopWatch.start();
            log.info("-------有人来了----------");
        }
    
        @Override
        public void requestDestroyed(ServletRequestEvent sre) {
            stopWatch.stop();
            log.info("-------有人出来了,耗时：{}----------", stopWatch.getTotalTimeSeconds());
    
            // todo:如果超过多少时间，发信息给开发者
            if (stopWatch.getTotalTimeSeconds() > 5) {
                // 换成创建机器人时 生成的WebHook
                DingTalkClient client = new DefaultDingTalkClient("https://oapi.dingtalk.com/robot/send?access_token=0e2273bd9a29c90bfa61ae71a48960b4b874c8f2a7fe68138e89d7b4d3ab6ad0");
                OapiRobotSendRequest request = new OapiRobotSendRequest();
                request.setMsgtype("text");
                OapiRobotSendRequest.Text text = new OapiRobotSendRequest.Text();
                text.setContent("停留时间过长——来自监控宝宝机器人");
                request.setText(text);
    //            OapiRobotSendRequest.At at = new OapiRobotSendRequest.At();
    //            at.setAtUserIds(Arrays.asList("4525xxxxxxxxx7041"));
    //            at.setIsAtAll(false);
    //            request.setAt(at);
                OapiRobotSendResponse response = null;
                try {
                    response = client.execute(request);
                } catch (ApiException e) {
                    e.printStackTrace();
                }
                System.out.println(response.getBody());
            }
        }
    }

### 结果展示 ###

![86caa1ec735d4f9da07e3cba0ec6af1b.png][]

[d306bf51ba82498d9851c46db30cb027.png]: https://img-blog.csdnimg.cn/d306bf51ba82498d9851c46db30cb027.png
[9ff01c1bd2fb4266bcaec4f44a54910d.png]: https://img-blog.csdnimg.cn/9ff01c1bd2fb4266bcaec4f44a54910d.png
[334533b5cfb443ebab426a6586173755.png]: https://img-blog.csdnimg.cn/334533b5cfb443ebab426a6586173755.png
[5a2850be67b544e18066cb74f689fce9.png]: https://img-blog.csdnimg.cn/5a2850be67b544e18066cb74f689fce9.png
[b35845ba8f6d4f0e8258c4678cbc7e79.png]: https://img-blog.csdnimg.cn/b35845ba8f6d4f0e8258c4678cbc7e79.png
[364af165a4114586a117036bcf90ea20.png]: https://img-blog.csdnimg.cn/364af165a4114586a117036bcf90ea20.png
[dab128662a40422686cb4f90f28492c6.png]: https://img-blog.csdnimg.cn/dab128662a40422686cb4f90f28492c6.png
[471bf346bfbc4b288531c19a779126aa.png]: https://img-blog.csdnimg.cn/471bf346bfbc4b288531c19a779126aa.png
[9f4d3bfc1da44e80af114ae23fc5bdc4.png]: https://img-blog.csdnimg.cn/9f4d3bfc1da44e80af114ae23fc5bdc4.png
[21b5ceccb96646d69e5dd3024b3b2a3c.png]: https://img-blog.csdnimg.cn/21b5ceccb96646d69e5dd3024b3b2a3c.png
[ed7515fe95aa4479b45bb463528ceb48.png]: https://img-blog.csdnimg.cn/ed7515fe95aa4479b45bb463528ceb48.png
[64d6a6ca66d94f229a06f24303426d48.png]: https://img-blog.csdnimg.cn/64d6a6ca66d94f229a06f24303426d48.png
[ea5b4ff4f008440d8f37883edfa16bb8.png]: https://img-blog.csdnimg.cn/ea5b4ff4f008440d8f37883edfa16bb8.png
[ed10ead8cc1b4230b7403cdf94232e6e.png]: https://img-blog.csdnimg.cn/ed10ead8cc1b4230b7403cdf94232e6e.png
[f76d09335c8a430c8450f571436d5067.png]: https://img-blog.csdnimg.cn/f76d09335c8a430c8450f571436d5067.png
[f63676becb494156a3eed33f428f87cd.png]: https://img-blog.csdnimg.cn/f63676becb494156a3eed33f428f87cd.png
[86caa1ec735d4f9da07e3cba0ec6af1b.png]: https://img-blog.csdnimg.cn/86caa1ec735d4f9da07e3cba0ec6af1b.png