pom.xml
================
        <!--dubbo依赖-->
        <dependency>
            <groupId>org.apache.dubbo</groupId>
            <artifactId>dubbo-spring-boot-starter</artifactId>
            <version>3.1.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.dubbo</groupId>
            <artifactId>dubbo</artifactId>
            <version>3.1.3</version>
        </dependency>




消费者 的xml配置
dubbo-userservice-client.xml
================
    <!--声明服务消费者名称-->
    <dubbo:application name="dubbo-userservice-client"></dubbo:application>

    <!--引用远程接口服务-->
    <dubbo:reference id="userService"
                     interface="com.bjpowernode.dubbo.service.UserService"
                     url="dubbo://localhost:20880"
                     registry="N/A"
                     check="false">
    </dubbo:reference>

启动时报错：
```
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userService': Invocation of init method failed; nested exception is java.lang.ClassCastException: org.apache.dubbo.config.RegistryConfig cannot be cast to [Ljava.lang.String;
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1804) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$222/1042790962.getObject(Unknown Source) ~[na:na]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:934) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918) ~[spring-context-5.3.20.jar:5.3.20]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.20.jar:5.3.20]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.5.14.jar:2.5.14]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:780) [spring-boot-2.5.14.jar:2.5.14]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:453) [spring-boot-2.5.14.jar:2.5.14]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:343) [spring-boot-2.5.14.jar:2.5.14]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1370) [spring-boot-2.5.14.jar:2.5.14]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1359) [spring-boot-2.5.14.jar:2.5.14]
	at com.bjpowernode.dubbo.client.dubbouserserviceclient.DubboUserserviceClientApplication.main(DubboUserserviceClientApplication.java:14) [classes/:na]
Caused by: java.lang.ClassCastException: org.apache.dubbo.config.RegistryConfig cannot be cast to [Ljava.lang.String;
	at org.apache.dubbo.config.spring.reference.ReferenceBeanSupport.convertReferenceProps(ReferenceBeanSupport.java:95) ~[dubbo-3.1.3.jar:3.1.3]
	at org.apache.dubbo.config.spring.reference.ReferenceCreator.populateBean(ReferenceCreator.java:168) ~[dubbo-3.1.3.jar:3.1.3]
	at org.apache.dubbo.config.spring.reference.ReferenceCreator.configureBean(ReferenceCreator.java:109) ~[dubbo-3.1.3.jar:3.1.3]
	at org.apache.dubbo.config.spring.reference.ReferenceCreator.build(ReferenceCreator.java:95) ~[dubbo-3.1.3.jar:3.1.3]
	at org.apache.dubbo.config.spring.reference.ReferenceBeanManager.initReferenceBean(ReferenceBeanManager.java:176) ~[dubbo-3.1.3.jar:3.1.3]
	at org.apache.dubbo.config.spring.reference.ReferenceBeanManager.addReference(ReferenceBeanManager.java:91) ~[dubbo-3.1.3.jar:3.1.3]
	at org.apache.dubbo.config.spring.ReferenceBean.afterPropertiesSet(ReferenceBean.java:240) ~[dubbo-3.1.3.jar:3.1.3]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1863) ~[spring-beans-5.3.20.jar:5.3.20]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1800) ~[spring-beans-5.3.20.jar:5.3.20]
	... 17 common frames omitted
```
按在线文档上说，registry="N/A"，有url直连配置，这个属性是可以省略的。去掉这个属性后，又报没有任何registry的错误。
if (providedByServices != null) {
                providedByInterfaceLength = ((String[]) providedByServices).length;
                providedByInterfaceServices = (String[]) providedByServices;
            }
            String[] providedbByServices = new String[providedByReferenceLength + providedByInterfaceLength];
            System.arraycopy(providedbBy.name(), 0, providedbByServices, 0, providedByReferenceLength);
            if (providedByInterfaceLength > 0) {
                System.arraycopy(providedByInterfaceServices, 0, providedbByServices, providedByReferenceLength, providedByInterfaceLength);
            }
            attributes.put(ReferenceAttributes.PROVIDED_BY, providedbByServices);
        }
        attributes.put(ReferenceAttributes.INTERFACE, interfaceName);
        attributes.remove(ReferenceAttributes.INTERFACE_NAME);
        attributes.remove(ReferenceAttributes.INTERFACE_CLASS);
        
        String generic = String.valueOf(defaultInterfaceClass == GenericService.class);
        String oldGeneric = attributes.containsValue(ReferenceAttributes.GENERIC) ?
            String.valueOf(attributes.get(ReferenceAttributes.GENERIC)) : "false";
        if (!StringUtils.isEquals(oldGeneric, generic)) {
            attributes.put(ReferenceAttributes.GENERIC, generic);
        }
        
        
        String[] registryIds = (String[]) attributes.get(ReferenceAttributes.REGISTRY);
        if (registryIds != null) {
            String value = join(registryIds, ",");
            attributes.remove(ReferenceAttributes.REGISTRY);
            attributes.put(ReferenceAttributes.REGISTRY_IDS, value);
        }
    }