dubbo和springcloud问题解决——interface not allow null

环境

dubbo版本： 2.7.3

springCloud版本： 2.2.0

复现步骤

当使用@Service注解注入dubbo provider到Spring容器中时，在dubbo provider的bean对象里依赖SpringCloud的bean时，触发报错，应用报错无法启动！

dubbo provider bean

@Service(registry = "dubbo-registry", interfaceClass = DubboProvideFacade.class)
public class DubboProviderServiceImpl implements DubboProvideFacade {
  @Resource
	private FeignClient feignClient;
  ······
}
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SpringCloud Client

@FeignClient(name = "feignClient", url = "${feign.client.config.url}", configuration = FeignClientInterceptor.class)
public interface FeignClient {
  	······
}
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报错

Caused by: java.lang.IllegalStateException:  interface not allow null!
	at org.apache.dubbo.config.ServiceConfig.checkAndUpdateSubConfigs(ServiceConfig.java:297)
	at org.apache.dubbo.config.ServiceConfig.export(ServiceConfig.java:358)
	at org.apache.dubbo.config.spring.ServiceBean.export(ServiceBean.java:327)
	at org.apache.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:105)
	at org.apache.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:51)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:402)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:408)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:359)
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:896)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:552)
	at org.springframework.cloud.context.named.NamedContextFactory.createContext(NamedContextFactory.java:136)
	at org.springframework.cloud.context.named.NamedContextFactory.getContext(NamedContextFactory.java:101)
	at org.springframework.cloud.context.named.NamedContextFactory.getInstance(NamedContextFactory.java:145)
	at org.springframework.cloud.openfeign.FeignClientFactoryBean.get(FeignClientFactoryBean.java:224)
	at org.springframework.cloud.openfeign.FeignClientFactoryBean.feign(FeignClientFactoryBean.java:85)
	at org.springframework.cloud.openfeign.FeignClientFactoryBean.getTarget(FeignClientFactoryBean.java:261)
	at org.springframework.cloud.openfeign.FeignClientFactoryBean.getObject(FeignClientFactoryBean.java:251)
	at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:171)
	... 142 common frames omitted
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原因

这个错误是由 Spring Cloud Feign 设计引起的，每个@FeignClient都会生成一个带有新子 Spring 的 Feign 代理，该子 SpringApplicationContext可能会在其 parent 之前刷新ApplicationContext。如果有注解@Service的 Dubbo 服务 bean 被子上下文扫描到，这个 DubboServiceBean也会被初始化，并且不能保证其依赖的 Spring bean 在那个时候已经准备好

解决方式

方式一（已验证）

将FeignClient使用ApplicationContextAware进行获取

首先写一个SpringBean获取工具类

@Component
public class SpringBeanUtil implements ApplicationContextAware {
    private static ApplicationContext appContext;

    private static boolean hasBean(String name){
        return appContext.containsBean(name);
    }

    public static Object getBeanByName(String name) throws BeansException {
        return appContext.getBean(name);
    }

    public static Object getBeanByType(Class requiredType) throws BeansException {
        return appContext.getBean(requiredType);
    }

    public static Object getBeanIfPresent(String name){
        if(hasBean(name)){
            return getBeanByName(name);
        }
        return null;
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        setAppContext(applicationContext);
    }

    private static synchronized void setAppContext(ApplicationContext appContext) {
        SpringBeanUtil.appContext = appContext;
    }
}
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通过Util获取FeignClient而不是Spring注入的方式

FeignClient client = SpringContextUtils.getBean(FeignClient.class)
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方式二

升级dubbo版本至2.7.9

据说在2.7.9解决了改问题

方式三

一个不完美的解决方法是，让FeignClient以懒注入的方式进行注入

@Service(registry = "dubbo-registry", interfaceClass = DubboProvideFacade.class)
public class DubboProviderServiceImpl implements DubboProvideFacade {
  @Resource
  @Lazy
	private FeignClient feignClient;
  ······
}
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