spring boot Appollo加载过程

学习Appollo是怎么加载配置的

com.ctrip.framework.apollo:apollo-client:1.0.0

Appollo 文档

先看一下spring.fatories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.ctrip.framework.apollo.spring.boot.ApolloAutoConfiguration
org.springframework.context.ApplicationContextInitializer=\
com.ctrip.framework.apollo.spring.boot.ApolloApplicationContextInitializer

org.springframework.context.ApplicationContextInitializer=
com.ctrip.framework.apollo.spring.boot.ApolloApplicationContextInitializer
这句是在项目已启动，配置信息加载完就执行ApolloApplicationContextInitializer类的initialize方法

ApolloApplicationContextInitializer

public class ApolloApplicationContextInitializer implements
    ApplicationContextInitializer<ConfigurableApplicationContext> {
  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", ConfigConsts.APOLLO_META_KEY};

  private final ConfigPropertySourceFactory configPropertySourceFactory = SpringInjector
      .getInstance(ConfigPropertySourceFactory.class);

  @Override
  public void initialize(ConfigurableApplicationContext context) {
    ConfigurableEnvironment environment = context.getEnvironment();

    initializeSystemProperty(environment);

    String enabled = environment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED, "false");
    if (!Boolean.valueOf(enabled)) {
      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);

    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);
    List<String> namespaceList = 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);
  }
}

首先看这块

String enabled = environment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED, "false");
    if (!Boolean.valueOf(enabled)) {
      logger.debug("Apollo bootstrap config is not enabled for context {}, see property: ${{}}", context, PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED);
      return;
    }

apollo.bootstrap.enabled = true

如果enabled 没有配置的话，直接返回。
看起来是不启动Appollo了，但是并不是。后面会讲。

然后就是这句
真正发起请求，到Appollo中心取配置信息

 Config config = ConfigService.getConfig(namespace);

接下来看
apollo.bootstrap.enabled = false 时，客户端是怎么样拉取配置的

@SpringBootApplication
@EnableApolloConfig
public class MainApplication {
    public static void main(String[] args) {
        SpringApplication sa = new SpringApplication(MainApplication.class);
        sa.addInitializers(new TestApplicationContextInitializer());
        sa.run(args);

    }
}

秘密就在 @EnableApolloConfig

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(ApolloConfigRegistrar.class)
public @interface EnableApolloConfig {
  /**
   * Apollo namespaces to inject configuration into Spring Property Sources.
   */
  String[] value() default {ConfigConsts.NAMESPACE_APPLICATION};

  /**
   * The order of the apollo config, default is {@link Ordered#LOWEST_PRECEDENCE}, which is Integer.MAX_VALUE.
   * If there are properties with the same name in different apollo configs, the apollo config with smaller order wins.
   * @return
   */
  int order() default Ordered.LOWEST_PRECEDENCE;
}

@Import：执行的时间点是在 ApolloApplicationContextInitializer 之后，其他Bean加载之前
再看下
ApolloConfigRegistrar
它实现了ImportBeanDefinitionRegistrar接口
可以通过BeanDefinitionRegistry 提前注册一些Bean定义到Spring容器里

public class ApolloConfigRegistrar implements ImportBeanDefinitionRegistrar {
  @Override
  public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
    AnnotationAttributes attributes = AnnotationAttributes.fromMap(importingClassMetadata
        .getAnnotationAttributes(EnableApolloConfig.class.getName()));
    String[] namespaces = attributes.getStringArray("value");
    int order = attributes.getNumber("order");
    PropertySourcesProcessor.addNamespaces(Lists.newArrayList(namespaces), order);

    BeanRegistrationUtil.registerBeanDefinitionIfNotExists(registry, PropertySourcesPlaceholderConfigurer.class.getName(),
        PropertySourcesPlaceholderConfigurer.class);

    BeanRegistrationUtil.registerBeanDefinitionIfNotExists(registry, PropertySourcesProcessor.class.getName(),
        PropertySourcesProcessor.class);

    BeanRegistrationUtil.registerBeanDefinitionIfNotExists(registry, ApolloAnnotationProcessor.class.getName(),
        ApolloAnnotationProcessor.class);

    BeanRegistrationUtil.registerBeanDefinitionIfNotExists(registry, SpringValueProcessor.class.getName(), SpringValueProcessor.class);
    BeanRegistrationUtil.registerBeanDefinitionIfNotExists(registry, SpringValueDefinitionProcessor.class.getName(), SpringValueDefinitionProcessor.class);

    BeanRegistrationUtil.registerBeanDefinitionIfNotExists(registry, ApolloJsonValueProcessor.class.getName(),
            ApolloJsonValueProcessor.class);
  }
}

先加载命名空间
再加载配置项
然后

BeanRegistrationUtil.registerBeanDefinitionIfNotExists(registry, PropertySourcesProcessor.class.getName(),
        PropertySourcesProcessor.class);

注册了，PropertySourcesProcessor会被提前加载

PropertySourcesProcessor

看下它
它实现了 BeanFactoryPostProcessor，EnvironmentAware， PriorityOrdered

• PriorityOrdered：定义加载顺序，也就是 有多个类实现了BeanFactoryPostProcessor接口的话，这个接口 会尽可能的先执行
• EnvironmentAware：注入Environment对象
• BeanFactoryPostProcessor：实现了postProcessBeanFactory方法。会在ApplicationContextInitializer 与 @Import加载的类之后执行

下面是PropertySourcesProcessor的代码

public class PropertySourcesProcessor implements BeanFactoryPostProcessor, EnvironmentAware, PriorityOrdered {
  private static final Multimap<Integer, String> NAMESPACE_NAMES = LinkedHashMultimap.create();
  private static final AtomicBoolean INITIALIZED = new AtomicBoolean(false);

  private final ConfigPropertySourceFactory configPropertySourceFactory = SpringInjector
      .getInstance(ConfigPropertySourceFactory.class);
  private final ConfigUtil configUtil = ApolloInjector.getInstance(ConfigUtil.class);
  private ConfigurableEnvironment environment;

  public static boolean addNamespaces(Collection<String> namespaces, int order) {
    return NAMESPACE_NAMES.putAll(order, namespaces);
  }

  @Override
  public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    if (INITIALIZED.compareAndSet(false, true)) {
      initializePropertySources();

      initializeAutoUpdatePropertiesFeature(beanFactory);
    }
  }

  private void initializePropertySources() {
    if (environment.getPropertySources().contains(PropertySourcesConstants.APOLLO_PROPERTY_SOURCE_NAME)) {
      //already initialized
      return;
    }
    CompositePropertySource composite = new CompositePropertySource(PropertySourcesConstants.APOLLO_PROPERTY_SOURCE_NAME);

    //sort by order asc
    ImmutableSortedSet<Integer> orders = ImmutableSortedSet.copyOf(NAMESPACE_NAMES.keySet());
    Iterator<Integer> iterator = orders.iterator();

    while (iterator.hasNext()) {
      int order = iterator.next();
      for (String namespace : NAMESPACE_NAMES.get(order)) {
        Config config = ConfigService.getConfig(namespace);

        composite.addPropertySource(configPropertySourceFactory.getConfigPropertySource(namespace, config));
      }
    }

    // add after the bootstrap property source or to the first
    if (environment.getPropertySources()
        .contains(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME)) {
      environment.getPropertySources()
          .addAfter(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME, composite);
    } else {
      environment.getPropertySources().addFirst(composite);
    }
  }

  private void initializeAutoUpdatePropertiesFeature(ConfigurableListableBeanFactory beanFactory) {
    if (!configUtil.isAutoUpdateInjectedSpringPropertiesEnabled()) {
      return;
    }

    AutoUpdateConfigChangeListener autoUpdateConfigChangeListener = new AutoUpdateConfigChangeListener(
        environment, beanFactory);

    List<ConfigPropertySource> configPropertySources = configPropertySourceFactory.getAllConfigPropertySources();
    for (ConfigPropertySource configPropertySource : configPropertySources) {
      configPropertySource.addChangeListener(autoUpdateConfigChangeListener);
    }
  }

  @Override
  public void setEnvironment(Environment environment) {
    //it is safe enough to cast as all known environment is derived from ConfigurableEnvironment
    this.environment = (ConfigurableEnvironment) environment;
  }

  //only for test
  private static void reset() {
    NAMESPACE_NAMES.clear();
    INITIALIZED.set(false);
  }

  @Override
  public int getOrder() {
    //make it as early as possible
    return Ordered.HIGHEST_PRECEDENCE;
  }
}

可以看到这里也有这段, 拉取配置的代码

Config config = ConfigService.getConfig(namespace);