spring boot微服務場景下apollo載入過程解析

implementation "com.ctrip.framework.apollo:apollo-client:1.6.0"

#應用的ID
app.id = java-project
# apollo 的 config-service 服務發現地址
apollo.meta = http://apollo.meta
# 啟用 apollo
apollo.bootstrap.enabled = true

# 在紀錄檔系統初始化前載入 apollo 設定
apollo.bootstrap.eagerLoad.enabled=true
# 載入的名稱空間，預設載入 application ，多個以逗號隔開
apollo.bootstrap.namespaces = application
# apollo 的安全拉取 secret 設定
apollo.accesskey.secret = xx
# 叢集設定
apollo.cluster = hk
# 快取路徑
apollo.cacheDir = /opt
# 是否保持和 apollo 設定頁面的設定順序一致
apollo.property.order.enable = true

public class ApolloApplicationContextInitializer implements ApplicationContextInitializer, EnvironmentPostProcessor, Ordered {
  public static final int DEFAULT_ORDER = 0;
  private static final Logger logger = LoggerFactory.getLogger(ApolloApplicationContextInitializer.class);
  private static final Splitter NAMESPACE_SPLITTER = Splitter.on(",").omitEmptyStrings().trimResults();
  private static final String[] APOLLO_SYSTEM_PROPERTIES = {"app.id", ConfigConsts.APOLLO_CLUSTER_KEY,
      "apollo.cacheDir", "apollo.accesskey.secret", ConfigConsts.APOLLO_META_KEY, PropertiesFactory.APOLLO_PROPERTY_ORDER_ENABLE};
  private final ConfigPropertySourceFactory configPropertySourceFactory = SpringInjector.getInstance(ConfigPropertySourceFactory.class);
  private int order = DEFAULT_ORDER;
  @Override
  public void initialize(ConfigurableApplicationContext context) {
    ConfigurableEnvironment environment = context.getEnvironment();
    if (!environment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED, Boolean.class, false)) {
      logger.debug("Apollo bootstrap config is not enabled for context {}, see property: ${{}}", context, PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED);
      return;
    }
    logger.debug("Apollo bootstrap config is enabled for context {}", context);
    initialize(environment);
  }
  /**
   * Initialize Apollo Configurations Just after environment is ready.
   *
   * @param environment
   */
  protected void initialize(ConfigurableEnvironment environment) {
    if (environment.getPropertySources().contains(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME)) {
      //already initialized
      return;
    }
    String namespaces = environment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_NAMESPACES, ConfigConsts.NAMESPACE_APPLICATION);
    logger.debug("Apollo bootstrap namespaces: {}", namespaces);
    ListnamespaceList = NAMESPACE_SPLITTER.splitToList(namespaces);
    CompositePropertySource composite = new CompositePropertySource(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME);
    for (String namespace : namespaceList) {
      Config config = ConfigService.getConfig(namespace);
      composite.addPropertySource(configPropertySourceFactory.getConfigPropertySource(namespace, config));
    }
    environment.getPropertySources().addFirst(composite);
  }
  /**
   * To fill system properties from environment config
   */
  void initializeSystemProperty(ConfigurableEnvironment environment) {
    for (String propertyName : APOLLO_SYSTEM_PROPERTIES) {
      fillSystemPropertyFromEnvironment(environment, propertyName);
    }
  }
  private void fillSystemPropertyFromEnvironment(ConfigurableEnvironment environment, String propertyName) {
    if (System.getProperty(propertyName) != null) {
      return;
    }
    String propertyValue = environment.getProperty(propertyName);
    if (Strings.isNullOrEmpty(propertyValue)) {
      return;
    }
    System.setProperty(propertyName, propertyValue);
  }
  /**
   *
   * In order to load Apollo configurations as early as even before Spring loading logging system phase,
   * this EnvironmentPostProcessor can be called Just After ConfigFileApplicationListener has succeeded.
   *
   * 
   * The processing sequence would be like this: 
   * Load Bootstrap properties and application properties -----> load Apollo configuration properties ----> Initialize Logging systems
   *
   * @param configurableEnvironment
   * @param springApplication
   */
  @Override
  public void postProcessEnvironment(ConfigurableEnvironment configurableEnvironment, SpringApplication springApplication) {
    // should always initialize system properties like app.id in the first place
    initializeSystemProperty(configurableEnvironment);
    Boolean eagerLoadEnabled = configurableEnvironment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_EAGER_LOAD_ENABLED, Boolean.class, false);
    //EnvironmentPostProcessor should not be triggered if you don't want Apollo Loading before Logging System Initialization
    if (!eagerLoadEnabled) {
      return;
    }
    Boolean bootstrapEnabled = configurableEnvironment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED, Boolean.class, false);
    if (bootstrapEnabled) {
      initialize(configurableEnvironment);
    }
  }
  /**
   * @since 1.3.0
   */
  @Override
  public int getOrder() {
    return order;
  }
  /**
   * @since 1.3.0
   */
  public void setOrder(int order) {
    this.order = order;
  }
}