Java servlet 和服务器发送的事件
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Java servlet and server sent events
提问by Chris
Is it possible to create a server sent event using java servlets so that a client could receive updates using:
是否可以使用 java servlet 创建服务器发送的事件，以便客户端可以使用以下方法接收更新：
<script>
var source = new EventSource('/events');
source.onmessage = function(e) {
document.body.innerHTML += e.data + '<br>';
};
</script>
All examples I have found on the web are using PHP but I would assume that it should work using Java's HTTP Servlet.
我在网上找到的所有示例都使用 PHP，但我认为它应该使用 Java 的 HTTP Servlet 工作。
回答by frewper
this does the trick.
这就是诀窍。
HTML
HTML
<!DOCTYPE html>
<html>
<body onload ="registerSSE()" >
<script>
function registerSSE()
{
alert('test 1');
var source = new EventSource('http://frewper:8080/hello/sse');
alert('Test2');
source.onmessage=function(event)
{
document.getElementById("result").innerHTML+=event.data + "<br />";
};
/*source.addEventListener('server-time',function (e){
alert('ea');
},true);*/
}
</script>
<output id ="result"></output>
</body>
</html>
Servlet :
小服务程序：
import java.io.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class sse extends HttpServlet
{
public void doPost(HttpServletRequest request, HttpServletResponse response)
{
try
{
System.out.println("SSE Demo");
response.setContentType("text/event-stream");
PrintWriter pw = response.getWriter();
int i=0;
while(true)
{
i++;
pw.write("event: server-time\n\n"); //take note of the 2 \n 's, also on the next line.
pw.write("data: "+ i + "\n\n");
System.out.println("Data Sent!!!"+i);
if(i>10)
break;
}
pw.close();
}catch(Exception e){
e.printStackTrace();
}
}
public void doGet(HttpServletRequest request,HttpServletResponse response)
{
doPost(request,response);
}
}
回答by user1987452
Server-Sent Events is a HTML5 feature. We say "HTML5", therefore it's just client side feature. So long server can set https respnse header "text/event-stream;charset=UTF-8","Connection", "keep-alive", then it is supported by server. You can set such header with Java Servlet. Here you can find a step for step guide on SSE with servlet
服务器发送事件是一项 HTML5 功能。我们说“HTML5”，因此它只是客户端功能。所以只要服务器可以设置https响应头“text/event-stream;charset=UTF-8”、“Connection”、“keep-alive”，那么服务器就支持了。您可以使用 Java Servlet 设置此类标头。 在这里您可以找到有关使用 servlet 的 SSE 的步骤指南的步骤
回答by Mario
I have created a very simple library that can be integrated within plain Java Servlets in Asynchronous mode, so no extra server threads are required for each client: https://github.com/mariomac/jeasse
我创建了一个非常简单的库，可以在异步模式下集成到普通的 Java Servlet 中，因此每个客户端都不需要额外的服务器线程：https: //github.com/mariomac/jeasse
It integrates the SseDispatcher (for point-to-point SSEs) and SseBroadcaster (for event broadcasting). An example of use:
它集成了 SseDispatcher（用于点对点 SSE）和 SseBroadcaster（用于事件广播）。使用示例：
public class TestServlet extends HttpServlet {
SseBroadcaster broadcaster = new SseBroadcaster();
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Scanner scanner = new Scanner(req.getInputStream());
StringBuilder sb = new StringBuilder();
while(scanner.hasNextLine()) {
sb.append(scanner.nextLine());
}
System.out.println("sb = " + sb);
broadcaster.broadcast("message",sb.toString());
}
//http://cjihrig.com/blog/the-server-side-of-server-sent-events/
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
broadcaster.addListener(req);
}
}
