跟着尚硅谷学习spring cloud Stream 启动880

报错内容

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sendMessageController': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'IMessageProviderServiceImpl': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'org.springframework.messaging.MessageChannel' available: expected single matching bean but found 2: nullChannel,errorChannel
    at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:337) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1422) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]

大致意思是找不到依赖...
在application.yml文件中配置如下：

bindings:
        output:
          destination: studyExchange
          content-type: application/json
          default-binder: defaultRabbit  # 如果是binder，defaultRabbit  会变红

service层代码

public interface IMessageProviderService {
    String send();
}

实现类impl代码,
我的错误是Source引入错了包，导致一直报错：expected single matching bean but found 2: nullChannel,errorChannel
错误包：import javax.xml.transform.Source;
正确包：import org.springframework.cloud.stream.messaging.Source;

package com.yanheng.springcloud.service.impl;

import com.yanheng.springcloud.service.IMessageProviderService;
import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.cloud.stream.messaging.Source; // 正确包

import javax.annotation.Resource;
import java.util.UUID;

@EnableBinding(Source.class) // 定义消息的推送通道
public class IMessageProviderServiceImpl implements IMessageProviderService {
    @Resource
    private MessageChannel output; // 消息发送通道

    @Override
    public String send() {
        String serial = UUID.randomUUID().toString();
        output.send(MessageBuilder.withPayload(serial).build());
        System.out.println("********serial: " + serial);
        return serial;
    }
}

controller层代码

@RestController
public class sendMessageController {
    @Resource
    private IMessageProviderService iMessageProviderService;

    @GetMapping(value = "/sendMsg")
    public String sendMessage() {
        return iMessageProviderService.send();
    }
}

找了两天也没在网络上找到正确的解决办法，有的说加@Compent，或者@Qualifier等注解，都是不可行的。希望能帮助需要的人。