已请求默认的资料夹，但没有适用于“ org.springframework.cloud.stream.messaging.DirectWithAttributesChannel”的资料夹

Question

我正在尝试使用Spring Cloud + Kafka Streams + Spring Boot 2创建最简单的问候世界。

我意识到我错过了基本概念。基本上，我了解到：

1-我需要定义一个出站流以将消息写到Kafka主题，并定义一个入站流以从Kafka主题中读取消息

public interface LoansStreams {

    String INPUT = "loans-in";
    String OUTPUT = "loans-out";

    @Input(INPUT)
    SubscribableChannel inboundLoans();

    @Output(OUTPUT)
    MessageChannel outboundLoans();

}

2-配置Spring Cloud Stream绑定到我的流

@EnableBinding(LoansStreams.class)
public class StreamsConfig {
}

3-配置Kafka属性

spring:
  cloud:
    stream:
      kafka:
        binder:
          brokers: localhost:9092
      bindings:
        loans-in:
          destination: loans
          contentType: application/json
        loans-out:
          destination: loans
          contentType: application/json

4-创建交换消息模型

@Getter @Setter @ToString @Builder
public class Loans {
    private long timestamp;
    private String result;
}

5-写给卡夫卡

@Service
@Slf4j
public class LoansService {
    private final LoansStreams loansStreams;
    public LoansService(LoansStreams loansStreams) {
        this.loansStreams = loansStreams;
    }
    public void sendLoan(final Loans loans) {
        log.info("Sending loans {}", loans);
        MessageChannel messageChannel = loansStreams.outboundLoans();
        messageChannel.send(MessageBuilder
                .withPayload(loans)
                .setHeader(MessageHeaders.CONTENT_TYPE, MimeTypeUtils.APPLICATION_JSON)
                .build());
    }
}

6-听卡夫卡主题

@Component
@Slf4j
public class LoansListener {

    @StreamListener(LoansStreams.INPUT)
    public void handleLoans(@Payload Loans loans) {
        log.info("Received results: {}", loans);

    }
}

我花了整整一天时间阅读一些博客，并且我认为以上代码至少是可行的。我不知道我是否真的在编码最好的方法。顺便说一句，我得到了该主题中提到的错误：

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2019-04-26 18:33:05.619 ERROR 14784 --- [  restartedMain] o.s.boot.SpringApplication               : Application run failed

org.springframework.context.ApplicationContextException: Failed to start bean 'outputBindingLifecycle'; nested exception is java.lang.IllegalStateException: A default binder has been requested, but there are no binders available for 'org.springframework.cloud.stream.messaging.DirectWithAttributesChannel' : , and no default binder has been set.

搜寻解决方案，我发现有人说要对StreamListe进行编码以返回模型，所以我将其替换为：

@StreamListener(LoansStreams.INPUT)
@SendTo("loans-out")
public KStream<?, Loans> process(KStream<?, Loans> l) {
    log.info("Received: {}", l);
    return l;
}

然后我得到的错误至少对我来说还不太清楚（先前的错误清楚地提到了一些活页夹问题）：

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2019-04-26 19:01:06.016 ERROR 13276 --- [  restartedMain] o.s.boot.SpringApplication               : Application run failed

java.lang.IllegalArgumentException: Method must be declarative
        at org.springframework.util.Assert.isTrue(Assert.java:118) ~[spring-core-5.1.6.RELEASE.jar:5.1.6.RELEASE]
        at org.springframework.cloud.stream.binder.kafka.streams.KafkaStreamsStreamListenerSetupMethodOrchestrator.validateStreamListenerMethod(KafkaStreamsStreamListenerSetupMethodOrchestrator.java:510) ~[spring-cloud-stream-binder-kafka-streams-2.1.2.RELEASE.jar:2.1.2.RELEASE]
        at org.springframework.cloud.stream.binder.kafka.streams.KafkaStreamsStreamListenerSetupMethodOrchestrator.orchestrateStreamListenerSetupMethod(KafkaStreamsStreamListenerSetupMethodOrchestrator.java:168) ~[spring-cloud-stream-binder-kafka-streams-2.1.2.RELEASE.jar:2.1.2.RELEASE]
        at org.springframework.cloud.stream.binding.StreamListenerAnnotationBeanPostProcessor.doPostProcess(StreamListenerAnnotationBeanPostProcessor.java:226) ~[spring-cloud-stream-2.1.2.RELEASE.jar:2.1.2.RELEASE]

万一它有帮助，我想提出这个想法来应用SAGAS，但这不是这个问题的重点。首先，我需要启动并运行基本程序。

*编辑

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.mybank</groupId>
    <artifactId>kafka-cloud-stream</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>kafka-cloud-stream</name>
    <description>Spring Cloud Stream With Kafka</description>

    <properties>
        <java.version>11</java.version>
        <spring-cloud.version>Greenwich.SR1</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-streams</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-stream</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-stream-binder-kafka-streams</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-stream-test-support</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-web -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <!-- version>5.1.5.RELEASE</version-->
        </dependency>

    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

Answer 1

“已请求默认的资料夹，但没有可用的资料夹...”，请添加以下依赖项。

    <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-stream-binder-kafka</artifactId>
    </dependency>

Answer 2

您可以在 application.yml（或 application.properties）中定义您的默认绑定器

spring:
  cloud:
    stream:
      bindings:
        ...
      default-binder: kafka