文章目录
- 一，概述
- 1.SSE是何方神圣？
- 2.sse与webscoket区别
- 二，实现过程
- 1.效果展示
- 2. 简要流程
- 3. 源码放送
- 4.完整项目
一，概述
1.SSE是何方神圣？
SSE 全称Server Sent Event，直译一下就是服务器发送事件。
其最大的特点，可以简单概括为两个
- 长连接
- 服务端可以向客户端推送信息
2.sse与webscoket区别
sse 是单通道，只能服务端向客户端发消息；而 webscoket 是双通道
那么为什么有了 webscoket 还要搞出一个 sse 呢？既然存在，必然有着它的优越之处
| sse | websocket |
|---|---|
| http 协议 | 独立的 websocket 协议 |
| 轻量，使用简单 | 相对复杂 |
| 默认支持断线重连 | 需要自己实现断线重连 |
| 文本传输 | 二进制传输 |
| 支持自定义发送的消息类型 | - |
二，实现过程
下面我们以springboot工程为例，实现服务器端不间断向客户端推送数据
1.效果展示
http://124.71.129.204:8080/index
2. 简要流程
3. 源码放送
SSE工具类
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Consumer;
import org.apache.commons.lang3.RandomStringUtils;
import org.springframework.http.MediaType;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
import lombok.extern.slf4j.Slf4j;
/**
* Server-Sent Events <BR>
* https://blog.csdn.net/hhl18730252820/article/details/126244274
*/
@Slf4j
public class SSEServer
{
/**
* 当前连接数
*/
private static AtomicInteger count = new AtomicInteger(0);
private static Map<String, SseEmitter> sseEmitterMap = new ConcurrentHashMap<>();
public static SseEmitter connect()
{
String userId = RandomStringUtils.randomAlphanumeric(10);
SseEmitter sseEmitter = new SseEmitter(0L); // 设置超时时间，0表示不过期，默认是30秒，超过时间未完成会抛出异常
// 注册回调
sseEmitter.onCompletion(completionCallBack(userId));
sseEmitter.onError(errorCallBack(userId));
sseEmitter.onTimeout(timeOutCallBack(userId));
sseEmitterMap.put(userId, sseEmitter);
log.info("create new sse connect ,current user:{}, count: {}", userId, count.incrementAndGet());
return sseEmitter;
}
public static void batchSendMessage(String message)
{
sseEmitterMap.forEach((k, v) -> {
try
{
v.send(message, MediaType.APPLICATION_JSON);
}
catch (IOException e)
{
log.error("user id:{}, send message error:{}", k, e.getMessage());
removeUser(k);
}
});
}
public static void removeUser(String userId)
{
sseEmitterMap.remove(userId);
log.info("remove user id:{}, count: {}", userId, count.decrementAndGet());
}
public static int getUserCount()
{
return count.intValue();
}
private static Runnable completionCallBack(String userId)
{
return () -> {
log.info("结束连接,{}", userId);
removeUser(userId);
};
}
private static Runnable timeOutCallBack(String userId)
{
return () -> {
log.info("连接超时,{}", userId);
removeUser(userId);
};
}
private static Consumer<Throwable> errorCallBack(String userId)
{
return throwable -> {
log.error("连接异常，{}", userId);
removeUser(userId);
};
}
}
sse接口
import java.util.concurrent.TimeUnit;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
import com.fly.hello.service.SSEServer;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import lombok.extern.slf4j.Slf4j;
@Slf4j
@Api(tags = "sse接口")
@RestController
@RequestMapping("/sse")
public class SSEController
{
long i = -1;
@ApiOperation("初始化")
@GetMapping("/connect/{userId}")
public SseEmitter connect(@PathVariable String userId)
{
SseEmitter sseEmitter = SSEServer.connect();
if (i < 0)
{
new Thread(() -> sendMessage()).start();
}
return sseEmitter;
}
private void sendMessage()
{
if (i < 0) // 保证仅触发一次
{
log.info("Server-Sent Events start");
while (true)
{
try
{
TimeUnit.MILLISECONDS.sleep(1000);
}
catch (InterruptedException e)
{
}
i = ++i % 101;
SSEServer.batchSendMessage(String.valueOf(i));
}
}
}
}
页面引用sse
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<link href="css/bootstrap.min.css" rel="stylesheet" type="text/css" />
<style>
body {
margin: 10;
font-size: 62.5%;
line-height: 1.5;
}
.blue-button {
background: #25A6E1;
padding: 3px 20px;
color: #fff;
font-size: 10px;
border-radius: 2px;
-moz-border-radius: 2px;
-webkit-border-radius: 4px;
border: 1px solid #1A87B9
}
table {
width: 60%;
}
th {
background: SteelBlue;
color: white;
}
td, th {
border: 1px solid gray;
font-size: 12px;
text-align: left;
padding: 5px 10px;
overflow: hidden;
white-space: nowrap;
text-overflow: ellipsis;
max-width: 200px;
white-space: nowrap;
text-overflow: ellipsis;
text-overflow: ellipsis;
}
</style>
</head>
<title>Hello World!</title>
<script>
let data = new EventSource("/sse/connect/001")
data.onmessage = function(event) {
document.getElementById("result").innerText = event.data + '%';
document.getElementById("my-progress").value = event.data;
}
</script>
<body>
<div class="wrapper-page">
<table align="center">
<tr>
<th colspan="4">Navigate</th>
</tr>
<tr>
<td><a href="/index" target="_self">index</a></td>
<td><a href="/404" target="_self">出错页面</a></td>
<td><a href="/doc.html" target="_blank">doc.html</a></td>
<td><a href="/h2-console" target="_blank">h2-console</a></td>
</tr>
</table>
<div class="ex-page-content text-center">
<h2 align="center">
<a href="index">reload</a>
<div><progress style="width: 60%" id="my-progress" value="0" max="100"></progress></div>
<div id="result"></div>
</h2>
<img src="show/girl" width="600" height="600" />
<img src="show/pic" width="600" height="600" />
</div>
</div>
</body>
</html>
4.完整项目
https://gitcode.com/00fly/springboot-hello
git clone https://gitcode.com/00fly/springboot-hello.git
有任何问题和建议，都可以向我提问讨论,大家一起进步，谢谢!
-over-
