java - Jersey SSE 客户端未接收到事件

Question

我已经使用 Jersey SSE 客户端编写了一个基本的 Java 应用程序来使用从 Node.js 服务器流式传输的 SSE(服务器发送的事件)。但是，我无法接收这些事件。为了验证服务器组件是否按预期工作，我按如下方式使用了 curl:

curl -v -H "Accept: text/event-stream" http://localhost:8080/events/

我得到以下响应:

*   Trying ::1...
* Connected to localhost (::1) port 8080 (#0)
> GET /events/ HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.43.0
> Accept: text/event-stream
> 
< HTTP/1.1 200 OK
< X-Powered-By: Express
< Content-Type: text/event-stream
< Cache-Control: no-cache
< Connection: keep-alive
< Date: Wed, 26 Apr 2017 17:12:00 GMT
< Transfer-Encoding: chunked
< 

event: ping
data: 0.6637400726922664

event: ping
data: 0.8538157046725585

我的 Java SSE 客户端代码如下(Java 8，Jersey Client 1.19.3，Jersey Media SSE 2.25.1):

import org.glassfish.jersey.media.sse.EventListener;
import org.glassfish.jersey.media.sse.EventSource;
import org.glassfish.jersey.media.sse.InboundEvent;
import org.glassfish.jersey.media.sse.SseFeature;

import javax.ws.rs.client.Client;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.WebTarget;

public class NodeCaptureSSE {

  public static void main(String[] args) {

    Client client = ClientBuilder.newBuilder().register(SseFeature.class).build();
    WebTarget target = client.target("http://localhost:8080/events/");
    EventSource eventSource = EventSource.target(target).build();
    EventListener listener = new EventListener() {
        @Override
        public void onEvent(InboundEvent inboundEvent) {
            System.out.println(inboundEvent.getName() + "; " + inboundEvent.readData(String.class));
        }
    };
    eventSource.register(listener, "ping");
    eventSource.open();
    System.out.println("Connected to SSE source...");
    try {
      Thread.sleep(25_000);
    }
    catch (InterruptedException ie) {
      System.err.println("Exception: " + ie.getMessage());
    }
    eventSource.close();
    System.out.println("Closed connection to SSE source");
  }
}

我在屏幕上看到的唯一输出是:

Connected to SSE source...

25 秒后退出。由于服务器正在流式传输命名事件(“ping”)，我在将监听器注册到事件源时指定了这一点。省略 eventSource.register(...); 的第二个参数没有做任何事情，尽管我没想到会这样。我还删除了 URL 中的结尾 /，但这会产生 404 Not Found(正如预期的那样)。我希望能得到任何正确方向的指示。

Answer 1

您的代码对我来说效果很好。事实上，我一直在拼命寻找这段代码，所以谢谢 ^_^ 哈哈哈。无论如何，我有一个 SSE 事件流输出时间事件，这是我的输出与您的代码的样子(我将 ping 更改为时间事件以附加到我的服务器)。

 Connected to SSE source...
time-event; Time is Thu Jul 20 10:10:37 CDT 2017
time-event; Time is Thu Jul 20 10:10:41 CDT 2017

问题很可能出在您的事件流和您用来指向它的 URL，而不是您的客户端 Java 代码。我注意到的另一件事是，在您的 curl 命令中，我没有看到那里的字符集规范。确保您的字符集设置为 UTF-8。这是我的 cmd 输出的样子:

这是我用来生成流的代码。

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.ws.http.HTTPException;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.PasswordAuthentication;
import java.util.Calendar;



    @SuppressWarnings("java.io.IOException")
    @WebServlet("/SSEServlet")
    public class SSEServlet extends HttpServlet {
        private static final long serialVersionUID = 1L;
        private boolean cancel;

        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException {

            System.out.println("You just entered the doGetMethod");
            response.setContentType("text/event-stream");
            response.setCharacterEncoding("UTF-8");
            PrintWriter printWriter = null;
            response.getBufferSize();


            while(true){
                try{
                    System.out.println("You just entered the while loop");
                    double randomNumber = Math.random()*10000;
                    printWriter = response.getWriter();

                    printWriter.print("event: time-event" + "\n");
                    printWriter.print("data: " + "Time is " + Calendar.getInstance().getTime() + "\n\n");
                    response.flushBuffer();
                    Thread.sleep((long)randomNumber);

                } catch (IOException | InterruptedException e){
                    e.printStackTrace();
                    break;
                }
            }
            System.out.println("Connection was aborted");
        }
    }