Spring Cloud Alibaba基础教程：支持的几种服务消费方式（RestTemplate、WebClient、Feign） | 程序猿DD

[dyc87112]

http://blog.didispace.com/spring-cloud-alibaba-2/

通过《Spring Cloud Alibaba基础教程：使用Nacos实现服务注册与发现》一文的学习，我们已经学会如何使用Nacos来实现服务的注册与发现，同时也介绍如何通过LoadBalancerClient接口来获取某个服务的具体实例，并根据实例信息来发起服务接口消费请求。但是这样的做法需要我们手工的去编写服务选取、链接拼接等繁琐的工作，对于开发人员来说非常的不友好。所以接下来，我们再来看看除

[UR0609]

大佬，我应用的主类，在启动方法写的时候，测试是好用的。当我直接把应用主类拿出来写，直接就404了。

[UR0609]

测试好用

测试不好用

[midKingKing]

@UR0609 大佬，我应用的主类，在启动方法写的时候，测试是好用的。当我直接把应用主类拿出来写，直接就404了。 你拿出来的controller要放在SpringBootApplicatio的启动类的下一级别的目录，否则不会自动扫描到，或者用扫描注解指定扫描路径

[dyc87112]

关于上面的问题，可以读一下很早之前写过的一篇：http://blog.didispace.com/springbootproject/

[midKingKing]

@dyc87112 关于上面的问题，可以读一下很早之前写过的一篇：http://blog.didispace.com/springbootproject/

我一直很好奇你名字里面翟的发音，是di二声还是zhai二声...

[dyc87112]

@midKingKing

@dyc87112 关于上面的问题，可以读一下很早之前写过的一篇：http://blog.didispace.com/springbootproject/

我一直很好奇你名字里面翟的发音，是di二声还是zhai二声...

都ok，多音字

[javareact]

@midKingKing

@dyc87112 关于上面的问题，可以读一下很早之前写过的一篇：http://blog.didispace.com/springbootproject/

我一直很好奇你名字里面翟的发音，是di二声还是zhai二声...

姓念zhai

[dodadoda]

使用feign的时候，@autowired注入client失败了

@EnableDiscoveryClient
@EnableFeignClients(basePackages = "com.sn.nacosdiscoveryclientfeign.interfaces")
@SpringBootApplication
public class NacosDiscoveryClientFeignApplication {

    public static void main(String[] args) {
        SpringApplication.run(NacosDiscoveryClientFeignApplication.class, args);
    }

}

这里是client代码

@FeignClient("nacos-discovery-server")
public interface Client {

    @GetMapping("/hello")
    String hello(@RequestParam String name);

}

这是controller代码

@RestController
@Slf4j
public class TestController {

    @Autowired
    Client client;

    @GetMapping("/test")
    public String hello() {
        return client.hello("sn");
    }
}

下面是错误信息

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'testController': Unsatisfied dependency expressed through field 'client'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.sn.nacosdiscoveryclientfeign.interfaces.Client': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: RequestParam.value() was empty on parameter 0 at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:586) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:372) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1341) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:572) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:495) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:759) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE] at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:780) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE] at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:333) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1277) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1265) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE] at com.sn.nacosdiscoveryclientfeign.NacosDiscoveryClientFeignApplication.main(NacosDiscoveryClientFeignApplication.java:14) [classes/:na] Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.sn.nacosdiscoveryclientfeign.interfaces.Client': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: RequestParam.value() was empty on parameter 0 at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:178) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:101) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1645) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getObjectForBeanInstance(AbstractAutowireCapableBeanFactory.java:1175) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:257) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:251) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.DefaultListableBeanFactory.addCandidateEntry(DefaultListableBeanFactory.java:1322) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1288) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1098) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1062) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:583) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] ... 19 common frames omitted Caused by: java.lang.IllegalStateException: RequestParam.value() was empty on parameter 0 at feign.Util.checkState(Util.java:128) ~[feign-core-9.5.1.jar:na] at org.springframework.cloud.openfeign.annotation.RequestParamParameterProcessor.processArgument(RequestParamParameterProcessor.java:63) ~[spring-cloud-openfeign-core-2.0.1.RELEASE.jar:2.0.1.RELEASE] at org.springframework.cloud.openfeign.support.SpringMvcContract.processAnnotationsOnParameter(SpringMvcContract.java:238) ~[spring-cloud-openfeign-core-2.0.1.RELEASE.jar:2.0.1.RELEASE] at feign.Contract$BaseContract.parseAndValidateMetadata(Contract.java:110) ~[feign-core-9.5.1.jar:na] at org.springframework.cloud.openfeign.support.SpringMvcContract.parseAndValidateMetadata(SpringMvcContract.java:133) ~[spring-cloud-openfeign-core-2.0.1.RELEASE.jar:2.0.1.RELEASE] at feign.Contract$BaseContract.parseAndValidatateMetadata(Contract.java:66) ~[feign-core-9.5.1.jar:na] at feign.ReflectiveFeign$ParseHandlersByName.apply(ReflectiveFeign.java:146) ~[feign-core-9.5.1.jar:na] at feign.ReflectiveFeign.newInstance(ReflectiveFeign.java:53) ~[feign-core-9.5.1.jar:na] at feign.Feign$Builder.target(Feign.java:218) ~[feign-core-9.5.1.jar:na] at org.springframework.cloud.openfeign.HystrixTargeter.target(HystrixTargeter.java:39) ~[spring-cloud-openfeign-core-2.0.1.RELEASE.jar:2.0.1.RELEASE] at org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance(FeignClientFactoryBean.java:223) ~[spring-cloud-openfeign-core-2.0.1.RELEASE.jar:2.0.1.RELEASE] at org.springframework.cloud.openfeign.FeignClientFactoryBean.getObject(FeignClientFactoryBean.java:244) ~[spring-cloud-openfeign-core-2.0.1.RELEASE.jar:2.0.1.RELEASE] at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:171) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE] ... 30 common frames omitted