Question

我有一个简单的代码，它可以在单击按钮后模拟数据处理：

@Route("long")
public class LongWait extends VerticalLayout {

    public LongWait() {
        Button processButton = new Button("Process");
        processButton.addClickListener(event -> process());
        add(processButton);
    }

    //imitates processing data: 
    //should sleep for 10 minutes and then add "finished" label
    //instead loose connection after 5 minutes
    private void process() {
        try {
            Thread.sleep(10 * 60 * 1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        add(new Label("finished"));
    }
}

问题是-“处理” 5分钟后，浏览器与服务器的连接松动。

为什么会发生这种情况以及如何避免呢？
（我真的必须处理大量数据。）

Vaadin：10.0.3
Tomcat：9.0.8
Java：1.8.0_162

UPD： process()方法完成后（已过去10分钟），我在日志中收到以下错误：

java.lang.UnsupportedOperationException: Confirmed duplicate message from the client. Expected sync id: 1, got 0. Message start: {"csrfToken":"964b296a-b3ab-48d2-b67f-5e46080f8949","rpc":[{"type":"event","node":4,"event":"click","data":{"event.shiftKey":false,"event.metaKey":false,"event.detail":1,"event.ctrlKey":false,"event.clientX":75,"event.clientY":42,"event.altKey":false,"event.button":0,"event.screenY":160,"event.screenX":76}}],"syncId":0,"clientId":0}
    at com.vaadin.flow.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:302)
    at com.vaadin.flow.server.communication.UidlRequestHandler.synchronizedHandleRequest(UidlRequestHandler.java:89)
    at com.vaadin.flow.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:40)
    at com.vaadin.flow.server.VaadinService.handleRequest(VaadinService.java:1487)
    at com.vaadin.flow.server.VaadinServlet.service(VaadinServlet.java:300)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:412)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1385)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

Answer 1

这里发生的是按钮单击侦听器是直接从HTTP请求运行的，对此请求将不会有任何响应，直到从单击侦听器返回为止。 HTTP请求通常在一分钟后超时。

解决此问题的最佳方法通常是使用Vaadin提供的服务器推送功能。这样可以使单击处理程序在单独的线程中开始缓慢的工作，然后立即返回。处理完成后，结果将分别推送到UI中。

您可以在https://vaadin.com/docs/v10/flow/advanced/tutorial-push-access.html中阅读有关此操作的概述。

Answer 2

感谢@SteffenHarbich建议使用单独的处理线程。
我在Server Push旁边使用了多线程，它运行得很好。

@Push
@Route("long")
public class LongWait extends VerticalLayout {

    private UI ui;

    public LongWait() {
        Button processButton = new Button("Process");
        processButton.addClickListener(event -> process());
        add(processButton);

        ui = UI.getCurrent();
    }

    //imitates processing data: 
    //sleeps for 10 minutes and then adds "finished" label
    private void process() {
        Thread thread = new Thread(() -> {

            try {
                Thread.sleep(10 * 60 * 1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            ui.access(() -> add(new Label("finished")));
            ui.push();
        });
        thread.start();
    }
}

长时间处理时，如何防止Vaadin 10松动？

2 个答案: