为什么集成流不订阅 from 频道？

Question

对我来说，这似乎是最简单的 spring 集成示例。我正在尝试向 si4demo 学习。但是当我运行它时，我得到这个异常：

Exception in thread "main" org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel 'application.inbox'.; nested exception is org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers

我哪里错了？定义的流程不会创建对收件箱频道的订阅吗？

import org.springframework.boot.SpringApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.integration.annotation.IntegrationComponentScan;
import org.springframework.integration.annotation.MessagingGateway;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.integration.dsl.IntegrationFlow;
import org.springframework.integration.dsl.IntegrationFlows;
import org.springframework.messaging.MessageChannel;

@Configuration
@ComponentScan
@IntegrationComponentScan
public class App {

    public static void main(String[] args) {

        try (ConfigurableApplicationContext ctx = SpringApplication.run(App.class, args)) {

            final Gateway gateway = ctx.getBean(Gateway.class);
            final String rs = gateway.send("hullo");
            System.out.println(rs);

        }

    }

    private static final String INBOX = "inbox";

    @MessagingGateway(defaultRequestChannel = INBOX)
    public interface Gateway {
        String send(String msg);
    }

    @Bean
    public IntegrationFlow flow() {
        return IntegrationFlows.from(INBOX)
                .transform(p -> "world")
                .get();
    }

    @Bean(name = INBOX)
    public MessageChannel inbox() {
        return new DirectChannel();
    }

}

Answer 1

看起来你错过了主要玩家 - @EnableIntegraion:

Starting with version 4.0, the @EnableIntegration annotation has been introduced, to allow the registration of Spring Integration infrastructure beans (see JavaDocs). This annotation is required when only Java & Annotation configuration is used, e.g. with Spring Boot and/or Spring Integration Messaging Annotation support and Spring Integration Java DSL with no XML integration configuration.

http://docs.spring.io/spring-integration/docs/4.3.0.BUILD-SNAPSHOT/reference/html/overview.html#configuration-enable-integration

为什么集成流不订阅 from 频道？

Why doesn't integration flow subscribe to the from channel?

java

spring

spring-integration

spring-dsl