spring boot注入jar包中的接口总是提示that could not be found

首先是在spring boot项目中注入的jar包中的接口

 @Controller
public class MessageTransferStationController {

    @Autowired
    private MessageClient messageClient;
}

其次，jar包中的MessageClient的源码

public interface MessageClient {
}

MessageClient分别有三个实现类

public class CoreMessageClient implements MessageClient {}


@Component
public class SpringMessageClientImpl extends CoreMessageClient implements MessageClient {}


public class Spring2MessageClientImpl extends CoreMessageClient implements MessageClient {}

当我在spring boot项目中注入MessageClient接口的时候，启动报错：

017-06-12 15:06:53.281 WARN 9780 --- [ main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'messageTransferStationController': Unsatisfied dependency expressed through field 'messageClient'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.sinosoft.messageclient.MessageClient' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
2017-06-12 15:06:53.283 INFO 9780 --- [ main] o.apache.catalina.core.StandardService : Stopping service Tomcat
2017-06-12 15:06:53.316 INFO 9780 --- [ main] utoConfigurationReportLoggingInitializer :

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2017-06-12 15:06:53.431 ERROR 9780 --- [ main] o.s.b.d.LoggingFailureAnalysisReporter :

APPLICATION FAILED TO START

Description:

Field messageClient in com.sinosoft.oa.message_transfer_station.web.MessageTransferStationController required a bean of type 'com.sinosoft.messageclient.MessageClient' that could not be found.

Action:

Consider defining a bean of type 'com.sinosoft.messageclient.MessageClient' in your configuration.

Process finished with exit code 1

请问各位大佬，为什么MessageClient为什么不能注入，我猜想过MessageClient的实现类没有被Spring管理，我看了jar包中源码有一个实现类加上了@Component注解

求教各位大佬，这是什么原因引起的？

注：引用jar包中的其它接口也测试过了，同样的错误，也就是说引用的这个jar包中的所有接口都没有被spring管理，或者没有扫描。

多次实验后，发现引进来的jar包没有被spring管理，即时jar包中有spring注解。
在主启动类上加入@ComponentScan("/")，问题得到了解决

在主启动方法上添加注解就可以了, 我是这么解决的:
@ComponentScan("com.aaa.coupons.service")
public class CouponsApplication extends WebMvcConfigurerAdapter{
}

项目A包明为com.gs.aaa，项目B包名为com.gs.bbb，项目A依赖B，把A项目启动APP移动到com.gs包下（以前在com.gs.aaa下）即可正常扫描B项目中的注解

纠正一下楼上的几个答案
用@ComponentScan的确能解决注入失败的问题，但如果注入的是feign接口（例如像做接口抽离到一个统一jar中去）
应该在主启动类上加@EnableFeignClients(basePackages = "你抽离的jar包的接口所在包目录")
亲测可用

我引用的是一个maven里面的接口,报这个错误

@楼主我有和你一样的问题，加上@ComponentScan("/") 还是不行

    //注入
    @Autowired
//@Qualifier("DefaultFastFileStorageClient")
protected FastFileStorageClient ffsClient;

    // 接口
    public interface FastFileStorageClient extends GenerateStorageClient {｝

    //实现类
    @Component

public class DefaultFastFileStorageClient extends DefaultGenerateStorageClient implements FastFileStorageClient {｝

报错：：
Description:

Field ffsClient in com.eharmony.iams.api.collect.ImageCollectController required a bean of type 'com.github.tobato.fastdfs.service.FastFileStorageClient' that could not be found.

Action:

Consider defining a bean of type 'com.github.tobato.fastdfs.service.FastFileStorageClient' in your configuration.

我也碰到这个问题了，怎么解决的啊？

这个问题我也遇到了，原因是因为Spring boot自动扫描注解只能扫描启动类所在的包及其子包，而通常情况下外部引用的jar包都不会在启动类的子包中，所以无法扫描到。如果是自己打包的jar包，可以考虑修改jar包的包名，将打包的jar包改成启动类的子包。其它包我也没想到好办法，如果有好办法麻烦告诉我一下。