技术创想106 | 源码剖析：理解Spring Cloud中的@RefreshScope

@RestController@RequestMapping("/config")@RefreshScopepublic class ConfigController {
    @Value("${useLocalCache:false}")    private boolean useLocalCache;
    @RequestMapping("/get")    public boolean get() {        return useLocalCache;    }}

2024-01-18 10:58:45.143  INFO 2289 --- [or-127.0.0.1-59] com.alibaba.nacos.common.remote.client   : [7ff5ec9b-478a-40e7-b505-77af547b7d6d_config-0] Receive server push request, request = ConfigChangeNotifyRequest, requestId = 1332024-01-18 10:58:45.144  INFO 2289 --- [or-127.0.0.1-59] c.a.n.client.config.impl.ClientWorker    : [7ff5ec9b-478a-40e7-b505-77af547b7d6d_config-0] [server-push] config changed. dataId=config-demo.yaml, group=DEFAULT_GROUP,tenant=null2024-01-18 10:58:45.144  INFO 2289 --- [or-127.0.0.1-59] com.alibaba.nacos.common.remote.client   : [7ff5ec9b-478a-40e7-b505-77af547b7d6d_config-0] Ack server push request, request = ConfigChangeNotifyRequest, requestId = 1332024-01-18 10:58:45.553  INFO 2289 --- [s.client.Worker] c.a.n.client.config.impl.ClientWorker    : [fixed-127.0.0.1_8848] [data-received] dataId=config-demo.yaml, group=DEFAULT_GROUP, tenant=, md5=00b77727c9b4a661b8ae12cd7de1395f, content=useLocalCache: true, type=yaml2024-01-18 10:58:45.557  INFO 2289 --- [ternal.notifier] c.a.nacos.client.config.impl.CacheData   : [fixed-127.0.0.1_8848] [notify-context] dataId=config-demo.yaml, group=DEFAULT_GROUP, md5=00b77727c9b4a661b8ae12cd7de1395f2024-01-18 10:58:45.557  INFO 2289 --- [s.client.Worker] c.a.nacos.client.config.impl.CacheData   : [fixed-127.0.0.1_8848] [notify-listener] time cost=0ms in ClientWorker, dataId=config-demo.yaml, group=DEFAULT_GROUP, md5=00b77727c9b4a661b8ae12cd7de1395f, listener=com.alibaba.cloud.nacos.refresh.NacosContextRefresher$1@e15133a 2024-01-18 10:58:45.770  WARN 2289 --- [ternal.notifier] c.a.c.n.c.NacosPropertySourceBuilder     : Ignore the empty nacos configuration and get it based on dataId[config-demo] & group[DEFAULT_GROUP]2024-01-18 10:58:46.093  INFO 2289 --- [ternal.notifier] b.c.PropertySourceBootstrapConfiguration : Located property source: [BootstrapPropertySource {name='bootstrapProperties-config-demo.yaml,DEFAULT_GROUP'}, BootstrapPropertySource {name='bootstrapProperties-config-demo,DEFAULT_GROUP'}]2024-01-18 10:58:46.255  INFO 2289 --- [ternal.notifier] o.s.boot.SpringApplication               : No active profile set, falling back to 1 default profile: "default"2024-01-18 10:58:46.264  INFO 2289 --- [ternal.notifier] o.s.boot.SpringApplication               : Started application in 0.685 seconds (JVM running for 119.187)2024-01-18 10:58:46.337  INFO 2289 --- [ternal.notifier] o.s.c.e.event.RefreshEventListener       : Refresh keys changed: [useLocalCache]2024-01-18 10:58:46.337  INFO 2289 --- [ternal.notifier] c.a.nacos.client.config.impl.CacheData   : [fixed-127.0.0.1_8848] [notify-ok] dataId=config-demo.yaml, group=DEFAULT_GROUP, md5=00b77727c9b4a661b8ae12cd7de1395f, listener=com.alibaba.cloud.nacos.refresh.NacosContextRefresher$1@e15133a ,cost=780 millis.

@Configuration(proxyBeanMethods = false)@ConditionalOnProperty(name = "spring.cloud.nacos.config.enabled", matchIfMissing = true)public class NacosConfigBootstrapConfiguration {
  ...
  @Bean  public NacosPropertySourceLocator nacosPropertySourceLocator(      NacosConfigManager nacosConfigManager) {    return new NacosPropertySourceLocator(nacosConfigManager);  }}

public class NacosPropertySourceLocator implements PropertySourceLocator {  @Override  public PropertySource<?> locate(Environment env) {    ...    CompositePropertySource composite = new CompositePropertySource(NACOS_PROPERTY_SOURCE_NAME);
    loadSharedConfiguration(composite);    loadExtConfiguration(composite);    loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);    return composite;  }}

private void registerNacosListener(final String groupKey, final String dataKey) {    String key = NacosPropertySourceRepository.getMapKey(dataKey, groupKey);    Listener listener = listenerMap.computeIfAbsent(key,        lst -> new AbstractSharedListener() {          @Override          public void innerReceive(String datad, String group,String configInfo) {            refreshCountIncrement();            nacosRefreshHistory.addRefreshRecord(dataId, group, configInfo);            applicationContext.publishEvent(new RefreshEvent(this, null, "Refresh Nacos config"));            ...          }        });    try {      configService.addListener(dataKey, groupKey, listener);    }    catch (NacosException e) {      ...    }}

public class RefreshEventListener implements SmartApplicationListener {  ...
  public void handle(RefreshEvent event) {    if (this.ready.get()) { // don't handle events before app is ready      log.debug("Event received " + event.getEventDesc());      Set<String> keys = this.refresh.refresh();      log.info("Refresh keys changed: " + keys);    }  }}

@Target({ ElementType.TYPE, ElementType.METHOD })@Retention(RetentionPolicy.RUNTIME)@Scope("refresh")@Documentedpublic @interface RefreshScope {
  /**   * @see Scope#proxyMode()   * @return proxy mode   */  ScopedProxyMode proxyMode() default ScopedProxyMode.TARGET_CLASS;
}

public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
  protected <T> T doGetBean(String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly) throws BeansException {      ...      if (mbd.isSingleton()) {          ...        }
        else if (mbd.isPrototype()) {          // It's a prototype -> create a new instance.          ...        }
        else {          String scopeName = mbd.getScope();          if (!StringUtils.hasLength(scopeName)) {            throw new IllegalStateException("No scope name defined for bean '" + beanName + "'");          }          Scope scope = this.scopes.gt(scopeName);          ...        }  }

public class GenericScope    implements Scope, BeanFactoryPostProcessor, BeanDefinitionRegistryPostProcessor, DisposableBean {  ...  @Override  public Object get(String name, ObjectFactory<?> objectFactory) {    BeanLifecycleWrapper value = this.cache.put(name, new BeanLifecycleWrapper(name, objectFactory));   // 存入缓存    this.locks.putIfAbsent(name, new ReentrantReadWriteLock());    try {      return value.getBean();    }    catch (RuntimeException e) {      this.errors.put(name, e);      throw e;    }  }
  private static class BeanLifecycleWrapper {    public Object getBean() {      if (this.bean == null) {        synchronized (this.name) {          if (this.bean == null) {            this.bean = this.objectFactory.getObject();  // 创建Bean          }        }      }      return this.bean;    }  }}

public abstract class ContextRefresher {  ...  public synchronized Set<String> refresh() {    Set<String> keys = refreshEnvironment(); // 将新配置加载到环境中    this.scope.refreshAll(); // 刷新配置    return keys;  }}

@ManagedResourcepublic class RefreshScope extends GenericScope    implements ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, Ordered {  ...
  @ManagedOperation(description = "Dispose of the current instance of all beans "      + "in this scope and force a refresh on next method execution.")  public void refreshAll() {    super.destroy();    this.context.publishEvent(new RefreshScopeRefreshedEvent());  }}

public class GenericScope    implements Scope, BeanFactoryPostProcessor, BeanDefinitionRegistryPostProcessor, DisposableBean {  ...  @Override  public void destroy() {    List<Throwable> errors = new ArrayList<Throwable>();    Collection<BeanLifecycleWrapper> wrappers = this.cache.clear(); // 清空RefreshScope的缓存，下次重新创建    ...}