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本文主要研究下springcloud的featuresEndpoint

/actuator/features

{  "enabled": [    {      "type": "com.netflix.discovery.EurekaClient",      "name": "Eureka Client",      "version": "1.8.8",      "vendor": null    },    {      "type": "org.springframework.cloud.client.discovery.composite.CompositeDiscoveryClient",      "name": "DiscoveryClient",      "version": "2.0.0.RC1",      "vendor": "Pivotal Software, Inc."    },    {      "type": "org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient",      "name": "LoadBalancerClient",      "version": "2.0.0.RC1",      "vendor": "Pivotal Software, Inc."    },    {      "type": "com.netflix.ribbon.Ribbon",      "name": "Ribbon",      "version": "2.2.5",      "vendor": null    },    {      "type": "feign.Feign",      "name": "Feign",      "version": null,      "vendor": null    }  ],  "disabled": []}复制代码

CommonsClientAutoConfiguration

spring-cloud-commons-2.0.0.RC1-sources.jar!/org/springframework/cloud/client/CommonsClientAutoConfiguration.java

@Configuration@AutoConfigureOrder(0)public class CommonsClientAutoConfiguration {	@Configuration	@EnableConfigurationProperties(DiscoveryClientHealthIndicatorProperties.class)	@ConditionalOnClass(HealthIndicator.class)	@ConditionalOnBean(DiscoveryClient.class)	@ConditionalOnProperty(value = "spring.cloud.discovery.enabled", matchIfMissing = true)	protected static class DiscoveryLoadBalancerConfiguration {		@Bean		@ConditionalOnProperty(value = "spring.cloud.discovery.client.health-indicator.enabled", matchIfMissing = true)		public DiscoveryClientHealthIndicator discoveryClientHealthIndicator(				DiscoveryClient discoveryClient, DiscoveryClientHealthIndicatorProperties properties) {			return new DiscoveryClientHealthIndicator(discoveryClient, properties);		}		@Bean		@ConditionalOnProperty(value = "spring.cloud.discovery.client.composite-indicator.enabled", matchIfMissing = true)		@ConditionalOnBean(DiscoveryHealthIndicator.class)		public DiscoveryCompositeHealthIndicator discoveryCompositeHealthIndicator(				HealthAggregator aggregator, List
    
      indicators) {			return new DiscoveryCompositeHealthIndicator(aggregator, indicators);		}		@Bean		public HasFeatures commonsFeatures() {			return HasFeatures.abstractFeatures(DiscoveryClient.class,					LoadBalancerClient.class);		}	}	@Configuration	@ConditionalOnClass(Endpoint.class)	@ConditionalOnProperty(value = "spring.cloud.features.enabled", matchIfMissing = true)	protected static class ActuatorConfiguration {		@Autowired(required = false)		private List
     
       hasFeatures = new ArrayList<>();		@Bean		@ConditionalOnEnabledEndpoint		public FeaturesEndpoint featuresEndpoint() {			return new FeaturesEndpoint(this.hasFeatures);		}	}}复制代码
     
    

这里有一个ActuatorConfiguration，用来注册featuresEndpoint

FeaturesEndpoint

spring-cloud-commons-2.0.0.RC1-sources.jar!/org/springframework/cloud/client/actuator/FeaturesEndpoint.java

@Endpoint(id = "features")public class FeaturesEndpoint		implements ApplicationContextAware {	private final List
    
      hasFeaturesList;	private ApplicationContext context;	public FeaturesEndpoint(List
     
       hasFeaturesList) {		this.hasFeaturesList = hasFeaturesList;	}	@Override	public void setApplicationContext(ApplicationContext context) throws BeansException {		this.context = context;	}	@ReadOperation	public Features features() {		Features features = new Features();		for (HasFeatures hasFeatures : this.hasFeaturesList) {			List
      
       > abstractFeatures = hasFeatures.getAbstractFeatures();			if (abstractFeatures != null) {				for (Class
        clazz : abstractFeatures) {					addAbstractFeature(features, clazz);				}			}			List
       
         namedFeatures = hasFeatures.getNamedFeatures();			if (namedFeatures != null) {				for (NamedFeature namedFeature : namedFeatures) {					addFeature(features, namedFeature);				}			}		}		return features;	}	private void addAbstractFeature(Features features, Class
         type) {		String featureName = type.getSimpleName();		try {			Object bean = this.context.getBean(type);			Class
         beanClass = bean.getClass();			addFeature(features, new NamedFeature(featureName, beanClass));		}		catch (NoSuchBeanDefinitionException e) {			features.getDisabled().add(featureName);		}	}	private void addFeature(Features features, NamedFeature feature) {		Class
         type = feature.getType();		features.getEnabled()				.add(new Feature(feature.getName(), type.getCanonicalName(),						type.getPackage().getImplementationVersion(),						type.getPackage().getImplementationVendor()));	}    //......}复制代码
       
      
     
    

这里通过hasFeaturesList来组装两类features，一类是abstractFeatures，另外一类是namedFeatures

HasFeatures

spring-cloud-commons-2.0.0.RC1-sources.jar!/org/springframework/cloud/client/actuator/HasFeatures.java

public class HasFeatures {	private final List
    
     > abstractFeatures = new ArrayList<>();	private final List
     
       namedFeatures = new ArrayList<>();	public static HasFeatures abstractFeatures(Class
      ... abstractFeatures) {		return new HasFeatures(Arrays.asList(abstractFeatures),				Collections.
      
        emptyList());	}	public static HasFeatures namedFeatures(NamedFeature... namedFeatures) {		return new HasFeatures(Collections.
       
        > emptyList(),				Arrays.asList(namedFeatures));	}	public static HasFeatures namedFeature(String name, Class
         type) {		return namedFeatures(new NamedFeature(name, type));	}	public static HasFeatures namedFeatures(String name1, Class
         type1, String name2,			Class
         type2) {		return namedFeatures(new NamedFeature(name1, type1),				new NamedFeature(name2, type2));	}	public HasFeatures(List
        
         > abstractFeatures,			List
         
           namedFeatures) { this.abstractFeatures.addAll(abstractFeatures); this.namedFeatures.addAll(namedFeatures); } public List
          
           > getAbstractFeatures() { return this.abstractFeatures; } public List
           
             getNamedFeatures() { return this.namedFeatures; }}复制代码
           
          
         
        
       
      
     
    

这里定义了两类features，一类是abstractFeatures，一类是namedFeatures

HasFeatures实例

spring-cloud-netflix-eureka-client-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/EurekaClientAutoConfiguration.java

@Configuration@EnableConfigurationProperties@ConditionalOnClass(EurekaClientConfig.class)@Import(DiscoveryClientOptionalArgsConfiguration.class)@ConditionalOnBean(EurekaDiscoveryClientConfiguration.Marker.class)@ConditionalOnProperty(value = "eureka.client.enabled", matchIfMissing = true)@AutoConfigureBefore({ NoopDiscoveryClientAutoConfiguration.class,		CommonsClientAutoConfiguration.class, ServiceRegistryAutoConfiguration.class })@AutoConfigureAfter(name = {
   "org.springframework.cloud.autoconfigure.RefreshAutoConfiguration",		"org.springframework.cloud.netflix.eureka.EurekaDiscoveryClientConfiguration",		"org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationAutoConfiguration"})public class EurekaClientAutoConfiguration {	private ConfigurableEnvironment env;	public EurekaClientAutoConfiguration(ConfigurableEnvironment env) {		this.env = env;	}	@Bean	public HasFeatures eurekaFeature() {		return HasFeatures.namedFeature("Eureka Client", EurekaClient.class);	}    //......}复制代码

比如eureka的client就注册了一个名为Eureka Client的namedFeature

小结

springcloud提供的featuresEndpoint，可以方便我们查看系统启动的一些features，进而了解系统特征。

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