others-how to resolve the `feign fallback class not found No fallback instance of type class` error when using feign with hystrix enabled ?

1. Purpose

In this post I would demonstrate how to resolve the following error when using feign with hystrix

Caused by: java.lang.IllegalStateException: No fallback instance of type class com.example.nacosfeign.clients.DemoClientFallback found for feign client nacos-provider-bswencw1



2. The solution

2.1 The details of the problem

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 :: Spring Boot ::       (v2.1.18.RELEASE)

2022-02-18 16:11:58.612  INFO 48538 --- [           main] c.e.nacosfeign.NacosFeignApplication     : No active profile set, falling back to default profiles: default
2022-02-18 16:11:59.964 ERROR 48538 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoController': Unsatisfied dependency expressed through field 'remoteClient'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.example.nacosfeign.clients.DemoClient': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: No fallback instance of type class com.example.nacosfeign.clients.DemoClientFallback found for feign client nacos-provider-bswencw1
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:598) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:376) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1402) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:591) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:514) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:321) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:319) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:866) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.1.18.RELEASE.jar:2.1.18.RELEASE]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:744) [spring-boot-2.1.18.RELEASE.jar:2.1.18.RELEASE]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:391) [spring-boot-2.1.18.RELEASE.jar:2.1.18.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) [spring-boot-2.1.18.RELEASE.jar:2.1.18.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.1.18.RELEASE.jar:2.1.18.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1204) [spring-boot-2.1.18.RELEASE.jar:2.1.18.RELEASE]
        at com.example.nacosfeign.NacosFeignApplication.main(NacosFeignApplication.java:12) [classes/:na]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
        at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run(AbstractRunMojo.java:543) [spring-boot-maven-plugin-2.1.18.RELEASE.jar:2.1.18.RELEASE]
        at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.example.nacosfeign.clients.DemoClient': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: No fallback instance of type class com.example.nacosfeign.clients.DemoClientFallback found for feign client nacos-provider-bswencw1
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:176) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:101) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1680) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getObjectForBeanInstance(AbstractAutowireCapableBeanFactory.java:1247) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:258) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.addCandidateEntry(DefaultListableBeanFactory.java:1501) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1458) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1239) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1196) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:595) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        ... 25 common frames omitted
Caused by: java.lang.IllegalStateException: No fallback instance of type class com.example.nacosfeign.clients.DemoClientFallback found for feign client nacos-provider-bswencw1
        at org.springframework.cloud.openfeign.HystrixTargeter.getFromContext(HystrixTargeter.java:81) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
        at org.springframework.cloud.openfeign.HystrixTargeter.targetWithFallback(HystrixTargeter.java:72) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
        at org.springframework.cloud.openfeign.HystrixTargeter.target(HystrixTargeter.java:49) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
        at org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance(FeignClientFactoryBean.java:243) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
        at org.springframework.cloud.openfeign.FeignClientFactoryBean.getTarget(FeignClientFactoryBean.java:272) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
        at org.springframework.cloud.openfeign.FeignClientFactoryBean.getObject(FeignClientFactoryBean.java:252) ~[spring-cloud-openfeign-core-2.2.1.RELEASE.jar:2.2.1.RELEASE]
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:169) ~[spring-beans-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        ... 36 common frames omitted

[WARNING] 
java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run(AbstractRunMojo.java:543)
        at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'demoController': Unsatisfied dependency expressed through field 'remoteClient'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.example.nacosfeign.clients.DemoClient': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: No fallback instance of type class com.example.nacosfeign.clients.DemoClientFallback found for feign client nacos-provider-bswencw1
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:598)
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90)
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:376)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1402)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:591)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:514)
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:321)
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:319)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:866)
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550)
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141)
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:744)
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:391)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:312)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1204)
        at com.example.nacosfeign.NacosFeignApplication.main(NacosFeignApplication.java:12)
        ... 6 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.example.nacosfeign.clients.DemoClient': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalStateException: No fallback instance of type class com.example.nacosfeign.clients.DemoClientFallback found for feign client nacos-provider-bswencw1
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:176)
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:101)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1680)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getObjectForBeanInstance(AbstractAutowireCapableBeanFactory.java:1247)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:258)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
        at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.addCandidateEntry(DefaultListableBeanFactory.java:1501)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1458)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1239)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1196)
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:595)
        ... 25 more
Caused by: java.lang.IllegalStateException: No fallback instance of type class com.example.nacosfeign.clients.DemoClientFallback found for feign client nacos-provider-bswencw1
        at org.springframework.cloud.openfeign.HystrixTargeter.getFromContext(HystrixTargeter.java:81)
        at org.springframework.cloud.openfeign.HystrixTargeter.targetWithFallback(HystrixTargeter.java:72)
        at org.springframework.cloud.openfeign.HystrixTargeter.target(HystrixTargeter.java:49)
        at org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance(FeignClientFactoryBean.java:243)
        at org.springframework.cloud.openfeign.FeignClientFactoryBean.getTarget(FeignClientFactoryBean.java:272)
        at org.springframework.cloud.openfeign.FeignClientFactoryBean.getObject(FeignClientFactoryBean.java:252)
        at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:169)
        ... 36 more




2.2 What is feign?

Feign is a declarative web service client. It makes writing web service clients easier. … Spring Cloud adds support for Spring MVC annotations and for using the same HttpMessageConverters used by default in Spring Web. Spring Cloud integrates Ribbon and Eureka to provide a load balanced http client when using Feign.

2.3 What is hystrix?

Hystrix isolates the points of access between the services, stops cascading failures across them and provides the fallback options.

2.4 Our feign client class and fallback class

Our feign client class:

@FeignClient(name="nacos-provider-bswencw1", configuration = FeignConfig.class, fallback = DemoClientFallback.class)
public interface DemoClient {
    @GetMapping("/hello/{name}")
    public Map<String, Object> hello(@PathVariable String name);
}

Our hystrix fallback class:

public class DemoClientFallback implements DemoClient {
    static Map<String, Object> map = new HashMap<>();
    static {
        map.put("result", "server is in maintainance , please try again later.");
    }

    @Override
    public Map<String, Object> hello(String name) {
        return map;
    }
}



2.5 The solution for this problem

Change our fallback class as follows:


@Component
public class DemoClientFallback implements DemoClient {
    static Map<String, Object> map = new HashMap<>();
    static {
        map.put("result", "server is in maintainance , please try again later.");
    }

    @Override
    public Map<String, Object> hello(String name) {
        return map;
    }
}

Because the fallback class must be a spring bean, then spring framework can access it from application context.


3. Summary

In this post, I demonstrated how to solve the feign fallback class not found No fallback instance of type class error when using feign with fallback. That’s it, thanks for your reading.

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