Spring cloud Hystrix注解初始化源码过程解读

@Deprecated
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(EnableCircuitBreakerImportSelector.class)
public @interface EnableCircuitBreaker {

}

@Order(Ordered.LOWEST_PRECEDENCE - 100)
public class EnableCircuitBreakerImportSelector extends SpringFactoryImportSelector<EnableCircuitBreaker> {

    @Override
    protected boolean isEnabled() {
        return getEnvironment().getProperty("spring.cloud.circuit.breaker.enabled", Boolean.class, Boolean.TRUE);
    }

}

public abstract class SpringFactoryImportSelector<T>
        implements DeferredImportSelector, BeanClassLoaderAware, EnvironmentAware {
    private final Log log = LogFactory.getLog(SpringFactoryImportSelector.class);
    private ClassLoader beanClassLoader;
    private Class<T> annotationClass;
    private Environment environment;
    @SuppressWarnings("unchecked")
    protected SpringFactoryImportSelector() {
        this.annotationClass = (Class<T>) GenericTypeResolver.resolveTypeArgument(this.getClass(),
                SpringFactoryImportSelector.class);
    }

@Override
    public String[] selectImports(AnnotationMetadata metadata) {
        //Enable参数没有打开的话就不加载
        if (!isEnabled()) {
            return new String[0];
        }
        AnnotationAttributes attributes = AnnotationAttributes
                .fromMap(metadata.getAnnotationAttributes(this.annotationClass.getName(), true));
        Assert.notNull(attributes, "No " + getSimpleName() + " attributes found. Is " + metadata.getClassName()
                + " annotated with @" + getSimpleName() + "?");
        // Find all possible auto configuration classes, filtering duplicates
        //SPI机制调用spring.factories文件下的EnableCircuitBreaker
        List<String> factories = new ArrayList<>(new LinkedHashSet<>(
                SpringFactoriesLoader.loadFactoryNames(this.annotationClass, this.beanClassLoader)));
        if (factories.isEmpty() && !hasDefaultFactory()) {
            throw new IllegalStateException("Annotation @" + getSimpleName()
                    + " found, but there are no implementations. Did you forget to include a starter?");
        }
        if (factories.size() > 1) {
            // there should only ever be one DiscoveryClient, but there might be more than
            // one factory
            this.log.warn("More than one implementation " + "of @" + getSimpleName()
                    + " (now relying on @Conditionals to pick one): " + factories);
        }
        return factories.toArray(new String[factories.size()]);
    }

/**
 * @author Spencer Gibb
 * @author Christian Dupuis
 * @author Venil Noronha
 */
@Configuration(proxyBeanMethods = false)
public class HystrixCircuitBreakerConfiguration {
    @Bean
    public HystrixCommandAspect hystrixCommandAspect() {
        return new HystrixCommandAspect();
    }
    @Bean
    public HystrixShutdownHook hystrixShutdownHook() {
        return new HystrixShutdownHook();
    }

@Aspect
public class HystrixCommandAspect {

@Pointcut("@annotation(com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand)")
    public void hystrixCommandAnnotationPointcut() {
    }
    @Pointcut("@annotation(com.netflix.hystrix.contrib.javanica.annotation.HystrixCollapser)")
    public void hystrixCollapserAnnotationPointcut() {
    }
    @Around("hystrixCommandAnnotationPointcut() || hystrixCollapserAnnotationPointcut()")
    public Object methodsAnnotatedWithHystrixCommand(final ProceedingJoinPoint joinPoint) throws Throwable {