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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": []}

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);        }    }}
     
    

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()));    }    //......}
       
      
     
    

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; }}
           
          
         
        
       
      
     
    

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);    }    //......}

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。

doc