java - Vert.x 如何将消息从 REST 传递/获取到消息总线？

Question

我想通过 REST 将消息传递给总线，然后取回它。但我无法正确设置消息总线接收器，它抛出 java.lang.IllegalStateException: Response has already been written。在现实生活中，消息总线应该从不同的来源接收消息并将消息传递给另一个目标。因此我们只需要将消息发布到总线上。但是如何正确读取消息并处理所有消息呢？例如，从 REST 界面:阅读该消息!我的简单应用启动:

 public static void main(String[] args) {
        Vertx vertx = Vertx.vertx();
        vertx.deployVerticle(new RESTVerticle());
        vertx.deployVerticle(new Receiver());
        EventBus eventBus = vertx.eventBus();
        eventBus.registerDefaultCodec(MessageDTO.class, new CustomMessageCodec());

    }

休息部分

public class RESTVerticle extends AbstractVerticle {

    private EventBus eventBus = null;

    @Override
    public void start() throws Exception {
        Router router = Router.router(vertx);
        eventBus = vertx.eventBus();
        router.route().handler(BodyHandler.create());
        router.route().handler(CorsHandler.create("*")
                .allowedMethod(HttpMethod.GET)
                .allowedHeader("Content-Type"));

        router.post("/api/message").handler(this::publishToEventBus);
       // router.get("/api/messagelist").handler(this::getMessagesFromBus);

        router.route("/*").handler(StaticHandler.create());
        vertx.createHttpServer().requestHandler(router::accept).listen(9999);
        System.out.println("Service running at 0.0.0.0:9999");

    }

private void publishToEventBus(RoutingContext routingContext) {
        System.out.println("routingContext.getBodyAsString() " + routingContext.getBodyAsString());
        final MessageDTO message = Json.decodeValue(routingContext.getBodyAsString(),
                MessageDTO.class);

        HttpServerResponse response = routingContext.response();
        response.setStatusCode(201)
                .putHeader("content-type", "application/json; charset=utf-8")
                .end(Json.encodePrettily(message));

        eventBus.publish("messagesBus", message);

    }

接收者:我把它移到另一个类，但这没有帮助

public class Receiver extends AbstractVerticle {

    @Override
    public void start() throws Exception {
        EventBus eventBus = vertx.eventBus();
        Router router = Router.router(vertx);

        router.route().handler(BodyHandler.create());
        router.route().handler(CorsHandler.create("*")
                .allowedMethod(HttpMethod.GET)
                .allowedHeader("Content-Type"));

        router.get("/api/messagelist").handler(this::getMessagesFromBus);
        router.route("/*").handler(StaticHandler.create());

        vertx.createHttpServer().requestHandler(router::accept).listen(9998);
        System.out.println("Service Receiver running at 0.0.0.0:9998");

private void getMessagesFromBus(RoutingContext routingContext) {
        EventBus eventBus = vertx.eventBus();
        eventBus.consumer("messagesBus", message -> {
            MessageDTO customMessage = (MessageDTO) message.body();
            HttpServerResponse response = routingContext.response();
            System.out.println("Receiver ->>>>>>>> " + customMessage);
            if (customMessage != null) {
                response.putHeader("content-type", "application/json; charset=utf-8")
                        .end(Json.encodePrettily(customMessage));
            }
            response.closed();

        });
    }

因此，如果我将消息发布到 REST 并且处理程序将其发布到总线，当我在运行时得到 http://localhost:9998/api/messagelist是返回json，但是第二次抛出异常

java.lang.IllegalStateException: Response has already been written
    at io.vertx.core.http.impl.HttpServerResponseImpl.checkWritten(HttpServerResponseImpl.java:561)
    at io.vertx.core.http.impl.HttpServerResponseImpl.putHeader(HttpServerResponseImpl.java:154)
    at io.vertx.core.http.impl.HttpServerResponseImpl.putHeader(HttpServerResponseImpl.java:52)
    at com.project.backend.Receiver.lambda$getMessagesFromBus$0(Receiver.java:55)
    at io.vertx.core.eventbus.impl.HandlerRegistration.handleMessage(HandlerRegistration.java:207)
    at io.vertx.core.eventbus.impl.HandlerRegistration.handle(HandlerRegistration.java:201)
    at io.vertx.core.eventbus.impl.EventBusImpl.lambda$deliverToHandler$127(EventBusImpl.java:498)
    at io.vertx.core.impl.ContextImpl.lambda$wrapTask$18(ContextImpl.java:335)
    at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:358)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:357)
    at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:112)
    at java.lang.Thread.run(Thread.java:745)

Receiver ->>>>>>>> Message{username=Aaaewfewf2d, message=41414wefwef2d2}

如何正确获取接收方的所有消息？或者如果总线收到消息，我应该立即将它们存储到数据库中吗？消息总线能否保留消息而不丢失它们？

谢谢

Answer 1

每次点击入口点“/api/messagelist”都会创建一个具有请求路由上下文的新消费者。

第一个请求将创建消费者并回复请求。当第二条消息发布时，该消费者将收到该消息并将回复先前的请求(实例)并且该请求已关闭。

我认为您误解了事件总线的用途，我真的建议您阅读文档。 http://vertx.io/docs/vertx-core/java/#event_bus