发表新帖
发表新帖

Java servlet and server sent events

前端 未结
关注
3 1101
醉酒成梦
醉酒成梦 2020-12-14 21:41

Is it possible to create a server sent event using java servlets so that a client could receive updates using:
相关标签:
3条回答
  • 北荒
    2020-12-14 21:58

    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

    It integrates the SseDispatcher (for point-to-point SSEs) and SseBroadcaster (for event broadcasting). An example of use:

    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);
}
}
    0 讨论(0)
  • 爱一瞬间的悲伤
    2020-12-14 22:02

    this does the trick.

    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 :

    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);
}

}
    0 讨论(0)
  • 我在风中等你
    2020-12-14 22:06

    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

    0 讨论(0)
 看不清?
提交回复
热议问题