springboot -sse -flux 服务器推送消息_async support must be enabled on a servlet and for

作者：笔触狂放9 | 2024-08-01 20:21:04

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async support must be enabled on a servlet and for all filters involved in a

先说BUG处理，遇到提示异步问题 Async support must be enabled on a servlet and for all filters involved in async request processing. This is done in Java code using the Servlet API or by adding "<async-supported>true</async-supported>" to servlet and filter declarations in web.xml.

springboot在@WebFilter注解处，加入urlPatterns = { "/*" },asyncSupported = true

springmvc在web.xml处理


<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
         version="3.0">
 
<filter-mapping>
  <filter-name>shiroFilter</filter-name>
  <url-pattern>/*</url-pattern>
  <dispatcher>REQUEST</dispatcher>
  <dispatcher>ASYNC</dispatcher>
</filter-mapping>

demo1，服务器间隔一定时间推送内容

接口方法


@GetMapping(path = "/sse/{userId}",produces = MediaType.TEXT_EVENT_STREAM_VALUE )
	public Flux<ServerSentEvent<String>> sse(@PathVariable String userId) {
        // 每两秒推送一次
        return Flux.interval(Duration.ofSeconds(2)).map(seq->
            Tuples.of(seq, LocalDateTime.now())).log()//序号和时间
                .map(data-> ServerSentEvent.<String>builder().id(userId).data(data.getT1().toString()).build());//推送内容
        
    }

2.前端代码


<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8"/>
    <title>服务器推送事件</title>
</head>
<body>
<div>    
    <div id="data"></div>    
    <div id="result"></div><br/>
</div>
<script th:inline="javascript" >
//服务器推送事件
if (typeof (EventSource) !== "undefined") { 
    var source1 = new EventSource("http://localhost:9000/api/admin/test/sse/1");
    //当抓取到消息时
    source1.onmessage = function (evt) {
        document.getElementById("data").innerHTML = document.getElementById("data").innerHTML+"股票行情：" + evt.data;
    };
} else {
    //注意：ie浏览器不支持
    document.getElementById("result").innerHTML = "抱歉，你的浏览器不支持 server-sent 事件...";  
    var xhr;
    var xhr2;
    if (window.XMLHttpRequest){
        //IE7+, Firefox, Chrome, Opera, Safari浏览器支持该方法
        xhr=new XMLHttpRequest();
        xhr2=new XMLHttpRequest();
    }else{
        //IE6, IE5 浏览器不支持，使用ActiveXObject方法代替
        xhr=new ActiveXObject("Microsoft.XMLHTTP");
        xhr2=new ActiveXObject("Microsoft.XMLHTTP");
    }
    console.log(xhr);
    console.log(xhr2);
    xhr.open('GET', '/sse/countDown');
    xhr.send(null);//发送请求
    xhr.onreadystatechange = function() {
        console.log("s响应状态：" + xhr.readyState);
        //2是空响应，3是响应一部分，4是响应完成
        if (xhr.readyState > 2) {
            //这儿可以使用response(对应json)与responseText（对应text）
            var newData = xhr.response.substr(xhr.seenBytes);
            newData = newData.replace(/\n/g, "#");
            newData = newData.substring(0, newData.length - 1);
            var data = newData.split("#");
            console.log("获取到的数据：" + data);
            document.getElementById("result").innerHTML = data;
            //长度重新赋值,下次截取时需要使用
            xhr.seenBytes = xhr.response.length;
        }
    }
        
    xhr2.open('GET', '/sse/retrieve');
    xhr2.send(null);//发送请求
    xhr2.onreadystatechange = function() {
        console.log("s响应状态：" + xhr2.readyState);
        //0: 请求未初始化，2 请求已接收，3 请求处理中，4  请求已完成，且响应已就绪
        if (xhr2.readyState > 2) {
            //这儿可以使用response(对应json)与responseText（对应text）
            var newData1 = xhr2.response.substr(xhr2.seenBytes);
            newData1 = newData1.replace(/\n/g, "#");
            newData1 = newData1.substring(0, newData1.length - 1);
            var data1 = newData1.split("#");
            console.log("获取到的数据：" + data1);
            document.getElementById("data").innerHTML = data1;
            //长度重新赋值,下次截取时需要使用
            xhr2.seenBytes = xhr2.response.length;
        }
    }
}
</script>
</body>
</html>

demo2 订阅服务器消息，服务器send推送消息完成后，关闭sse.close

1.接口方法以及工具类


@GetMapping(path = "/sse/sub",produces = MediaType.TEXT_EVENT_STREAM_VALUE )
public SseEmitter subscribe(@RequestParam String questionId,HttpServletResponse response) {
		// 简单异步发消息 ====
        //questionId 订阅id，id对应了sse对象
        new Thread(() -> {
            try {
                Thread.sleep(1000);
                for (int i = 0; i < 10; i++) {
                    Thread.sleep(500);
                    SSEUtils.pubMsg(questionId, questionId + " - kingtao come " + i);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                // 消息发送完关闭订阅
                SSEUtils.closeSub(questionId);
            }
        }).start();
        // =================
 
        return SSEUtils.addSub(questionId);
    }

工具类


import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
 
public class SSEUtils {
    // timeout
    private static Long DEFAULT_TIME_OUT = 2*60*1000L;
    // 订阅表
    private static Map<String, SseEmitter> subscribeMap = new ConcurrentHashMap<>();
 
    /** 添加订阅 */
    public static SseEmitter addSub(String questionId) {
        if (null == questionId || "".equals(questionId)) {
            return null;
        }
 
        SseEmitter emitter = subscribeMap.get(questionId);
        if (null == emitter) {
            emitter = new SseEmitter(DEFAULT_TIME_OUT);
            subscribeMap.put(questionId, emitter);
        }
 
        return emitter;
    }
 
    /** 发消息 */
    public static void pubMsg(String questionId, String msg) {
        SseEmitter emitter = subscribeMap.get(questionId);
        if (null != emitter) {
            try {
                // 更规范的消息结构看源码
                emitter.send(SseEmitter.event().data(msg));
            } catch (Exception e) {
                // e.printStackTrace();
            }
        }
    }
 
    /**
     * 关闭订阅 
     * @param questionId
     */
    public static void closeSub(String questionId) {
        SseEmitter emitter = subscribeMap.get(questionId);
        if (null != emitter) {
            try {
                emitter.complete();
                subscribeMap.remove(questionId);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

2.前端代码


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>sse</title>
</head>
<body>
<div>
    <label>问题id</label>
    <input type="text" id="questionId">
    <button onclick="subscribe()">订阅</button>
    <hr>
    <label>F12-console控制台查看消息</label>
</div>
 
<script>
    function subscribe() {
        let questionId = document.getElementById('questionId').value;
        let url = 'http://localhost:9000/api/admin/test/sse/sub?questionId=' + questionId;
        
        let eventSource = new EventSource(url);
        eventSource.onmessage = function (e) {
            console.log(e.data);
        };
 
        eventSource.onopen = function (e) {
			 console.log(e,1);
            // todo
        };
 
        eventSource.onerror = function (e) {
            // todo
						 console.log(e,2);
            eventSource.close()
        };
    }
</script>
</body>
</html>

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