Failed to introspect class feignclientfactorybean exception troubleshooting

Wrong statement

BeanCreationException: Error creating bean with name 'com.xxx.XxxClient': 
Lookup method resolution failed; 
nested exception is java.lang.IllegalStateException: Failed to introspect Class [org.springframework.cloud.openfeign.FeignClientFactoryBean] from ClassLoader [sun.misc.Launcher$AppClassLoader]

The visible reason is FeignClientFactoryBean introspect Failure

 introspection (Introspector) yes Java Language pairs Bean Class properties 、 A default handling method of event 
 Introspection is also called runtime type checking 
 Similar reflection , But reflection destroys Bean And introspectively follow the Convention 

Code scenario

package com.xxx;
@FeignClient(value = "vxxx",contextId ="idxxx")
public interface XxxClient extends XxxFeignApi {
}

 Start class scan 
@EnableFeignClients(basePackages = {"com.xxx"})

Investigation thought

1. see BeanDefinition Whether to create , That is, whether FeignClient class
2. see FactoryBean Whether to instantiate
3. see FactoryBean Of getObject Whether the method performs , That is, whether to instantiate Bean

Scan

Check the entrance run Method

run  The method focuses on 
this.refreshContext(context);
 Commission execution 
this.refresh(context);
 Continue to entrust 
((AbstractApplicationContext)applicationContext).refresh();
AbstractApplicationContext extends DefaultResourceLoader implements ConfigurableApplicationContext
 call  AbstractApplicationContext   Of  refresh  Method 
 Its template method definition calls  this.invokeBeanFactoryPostProcessors(beanFactory);
 Here is spring The extension point 
 Enter during initialization  PostProcessorRegistrationDelegate  class 
 Finally, entrust  ConfigurationClassPostProcessor  class , Its  parse  Method 
metadata = doProcessConfigurationClass(configClass, metadata);
 perform  doProcessConfigurationClass  Method 
 It will carry out  processImports  Methods to import various import class 
invokeBeanFactoryPostProcessors

Check the scanning class FeignClientsRegistrar

@Import(FeignClientsRegistrar.class)
public @interface EnableFeignClients {...}
 adopt import Inject scan class 
class FeignClientsRegistrar
		implements ImportBeanDefinitionRegistrar, ResourceLoaderAware, EnvironmentAware {
  //  Mainly through the hook method to scan  feignClient  Generate  BeanDefinition 
  //  adopt  ImportBeanDefinitionRegistrar  Of  registerBeanDefinitions  Method added to  BeanDefinitionRegistry
  	@Override
	public void registerBeanDefinitions(AnnotationMetadata metadata,
			BeanDefinitionRegistry registry) {
		registerDefaultConfiguration(metadata, registry);
		//  Add here  BeanDefinition 
		registerFeignClients(metadata, registry);
	}
}

ImportBeanDefinitionRegistrar Interface

spring The extension point , Support custom logic encapsulation  BeanDefinition object ; The class that implements this interface will call back postProcessBeanDefinitionRegistry Method 
 Scanned  feignClient  It is put in when registering  FactoryBean

Solution ： Unify caller and callee openfeign Dependent package version

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
            <version>xxx</version>
        </dependency>
                <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-openfeign-core</artifactId>
            <version>xxx</version>
        </dependency>