1. 特性
2. Spring Cloud 上下文
3. Spring Cloud 配置信息

Spring Cloud序幕

版本信息

Spring Cloud : Hoxton.SR1

Spring Boot : 2.2.2.RELEASE

特性

• 分布式/版本配置
• 服务注册和发现
• 路由
• 服务调用
• 负载均衡
• 短路
• 分布式消息

Spring Boot Actuator

端点

• /actuator/beans bean的端点
• /actuator/env 环境的端点

配置信息

• management.endpoints.web.exposure.include web暴露的外部端点，默认是info和health

Spring Cloud 上下文

回顾Spring Mvc上下文

Root WebApplicationContext (Service、Respostory)

• Servlet WebApplicationContext (Controller)

public class MyWebAppInitializer extends
AbstractAnnotationConfigDispatcherServletInitializer {
    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class<?>[] { RootConfig.class };
    }
    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class<?>[] { App1Config.class };
    }
    @Override
    protected String[] getServletMappings() {
        return new String[] { "/app1/*" };
    }
}

/actuator/beans bean的端点信息

{
    "contexts": {
        "application-1": {
            "beans": {},
            "parentId": "bootstrap"
        },
        "bootstrap": {}
    }
}

bootstrap ApplicationContext

• application-1 ApplicationContext

加载类BootstrapApplicationListener

事件驱动ApplicationEnvironmentPreparedEvent

• 创建bootstrap ApplicationContext，默认是从ContextIdApplicationContextInitializer生成上下文的名称，后强制修改为bootstrap

  private ConfigurableApplicationContext bootstrapServiceContext(
          ConfigurableEnvironment environment, final SpringApplication application,
          String configName) {
      StandardEnvironment bootstrapEnvironment = new StandardEnvironment();
      MutablePropertySources bootstrapProperties = bootstrapEnvironment
              .getPropertySources();
      for (PropertySource<?> source : bootstrapProperties) {
          bootstrapProperties.remove(source.getName());
      }
      String configLocation = environment
              .resolvePlaceholders("${spring.cloud.bootstrap.location:}");
      Map<String, Object> bootstrapMap = new HashMap<>();
      bootstrapMap.put("spring.config.name", configName);
      // if an app (or test) uses spring.main.web-application-type=reactive, bootstrap
      // will fail
      // force the environment to use none, because if though it is set below in the
      // builder
      // the environment overrides it
      bootstrapMap.put("spring.main.web-application-type", "none");
      if (StringUtils.hasText(configLocation)) {
          bootstrapMap.put("spring.config.location", configLocation);
      }
      bootstrapProperties.addFirst(
              new MapPropertySource(BOOTSTRAP_PROPERTY_SOURCE_NAME, bootstrapMap));
      for (PropertySource<?> source : environment.getPropertySources()) {
          if (source instanceof StubPropertySource) {
              continue;
          }
          bootstrapProperties.addLast(source);
      }
      // TODO: is it possible or sensible to share a ResourceLoader?
      SpringApplicationBuilder builder = new SpringApplicationBuilder()
              .profiles(environment.getActiveProfiles()).bannerMode(Mode.OFF)
              .environment(bootstrapEnvironment)
              // Don't use the default properties in this builder
              .registerShutdownHook(false).logStartupInfo(false)
              .web(WebApplicationType.NONE);
      final SpringApplication builderApplication = builder.application();
      if (builderApplication.getMainApplicationClass() == null) {
          // gh_425:
          // SpringApplication cannot deduce the MainApplicationClass here
          // if it is booted from SpringBootServletInitializer due to the
          // absense of the "main" method in stackTraces.
          // But luckily this method's second parameter "application" here
          // carries the real MainApplicationClass which has been explicitly
          // set by SpringBootServletInitializer itself already.
          builder.main(application.getMainApplicationClass());
      }
      if (environment.getPropertySources().contains("refreshArgs")) {
          // If we are doing a context refresh, really we only want to refresh the
          // Environment, and there are some toxic listeners (like the
          // LoggingApplicationListener) that affect global static state, so we need a
          // way to switch those off.
          builderApplication
                  .setListeners(filterListeners(builderApplication.getListeners()));
      }
      builder.sources(BootstrapImportSelectorConfiguration.class);
      final ConfigurableApplicationContext context = builder.run();
      // gh-214 using spring.application.name=bootstrap to set the context id via
      // `ContextIdApplicationContextInitializer` prevents apps from getting the actual
      // spring.application.name
      // during the bootstrap phase.
      // 从application或者spring.application.name(ContextIdApplicationContextInitializer类生成的) 调整为bootstrap
      context.setId("bootstrap");
      // Make the bootstrap context a parent of the app context
      addAncestorInitializer(application, context);
      // It only has properties in it now that we don't want in the parent so remove
      // it (and it will be added back later)
      bootstrapProperties.remove(BOOTSTRAP_PROPERTY_SOURCE_NAME);
      mergeDefaultProperties(environment.getPropertySources(), bootstrapProperties);
      return context;
  }

• 赋值父上下文

  private void addAncestorInitializer(SpringApplication application,
          ConfigurableApplicationContext context) {
      boolean installed = false;
      for (ApplicationContextInitializer<?> initializer : application
              .getInitializers()) {
          if (initializer instanceof AncestorInitializer) {
              installed = true;
              // New parent,将 bootstrap上下文作为父上下文传入
              ((AncestorInitializer) initializer).setParent(context);
          }
      }
      if (!installed) {
          application.addInitializers(new AncestorInitializer(context));
      }
  
  }
  
  
  private static class AncestorInitializer implements
          ApplicationContextInitializer<ConfigurableApplicationContext>, Ordered {
  
      private ConfigurableApplicationContext parent;
  
      AncestorInitializer(ConfigurableApplicationContext parent) {
          this.parent = parent;
      }
  
      public void setParent(ConfigurableApplicationContext parent) {
          this.parent = parent;
      }
  
      @Override
      public int getOrder() {
          // Need to run not too late (so not unordered), so that, for instance, the
          // ContextIdApplicationContextInitializer runs later and picks up the merged
          // Environment. Also needs to be quite early so that other initializers can
          // pick up the parent (especially the Environment).
          return Ordered.HIGHEST_PRECEDENCE + 5;
      }
  
      @Override
      public void initialize(ConfigurableApplicationContext context) {
          while (context.getParent() != null && context.getParent() != context) {
              context = (ConfigurableApplicationContext) context.getParent();
          }
          reorderSources(context.getEnvironment());
          new ParentContextApplicationContextInitializer(this.parent)
                  .initialize(context);
      }
  
      private void reorderSources(ConfigurableEnvironment environment) {
          PropertySource<?> removed = environment.getPropertySources()
                  .remove(DEFAULT_PROPERTIES);
          if (removed instanceof ExtendedDefaultPropertySource) {
              ExtendedDefaultPropertySource defaultProperties = (ExtendedDefaultPropertySource) removed;
              environment.getPropertySources().addLast(new MapPropertySource(
                      DEFAULT_PROPERTIES, defaultProperties.getSource()));
              for (PropertySource<?> source : defaultProperties.getPropertySources()
                      .getPropertySources()) {
                  if (!environment.getPropertySources().contains(source.getName())) {
                      environment.getPropertySources().addBefore(DEFAULT_PROPERTIES,
                              source);
                  }
              }
          }
      }
  
  }

Spring Cloud 配置信息

• application.yml配置

  management:
    endpoints:
      web:
        exposure:
          include: health,info,beans,env
  spring:
    application:
      name: application-name

• bootstrap.yml配置

  server:
    port: 8080
  spring:
    application:
      name: bootstrap-name

/actuator/env 环境的端点

{
    "activeProfiles": [],
    "propertySources": [{
            "name": "server.ports",
            "properties": {}
        }, {
            "name": "servletContextInitParams",
            "properties": {}
        }, {
            "name": "systemProperties",
            "properties": {}
        }, {
            "name": "systemEnvironment",
            "properties": {}
        }, {
            "name": "configServerClient",
            "properties": {}
        }, {
            "name": "springCloudClientHostInfo",
            "properties": {}
        }, {
            "name": "applicationConfig: [classpath:/application.yml]",
            "properties": {}
        }, {
            "name": "applicationConfig: [classpath:/bootstrap.yml]",
            "properties": {}
        }, {
            "name": "springCloudDefaultProperties",
            "properties": {}
        }
    ]
}

从上述配置来看，bootstrap的配置文件的优先级在application的配置文件之下。

自定义bootstrap配置

1. 实现PropertySourceLocator接口

   /**
    * 自定义实现
    *
    * @author FelixFly 2019/12/22
    */
   @Configuration
   public class CustomPropertySourceLocator implements PropertySourceLocator {
   
       @Override
       public PropertySource<?> locate(Environment environment) {
           return new MapPropertySource("customProperty",
                   Collections.singletonMap("spring.application.name", "custom-bootstrap"));
       }
   
   }

2. 配置META-INF\spring.factories文件

   org.springframework.cloud.bootstrap.BootstrapConfiguration=\
   top.felixfly.springcloud.context.CustomPropertySourceLocator

3. /actuator/env 环境的端点信息

   {
       "activeProfiles": [],
       "propertySources": [{
               "name": "server.ports",
               "properties": {}
           }, {
               "name": "bootstrapProperties-customProperty",
               "properties": {}
           }, {
               "name": "servletContextInitParams",
               "properties": {}
           }, {
               "name": "systemProperties",
               "properties": {}
           }, {
               "name": "systemEnvironment",
               "properties": {}
           }, {
               "name": "configServerClient",
               "properties": {}
           }, {
               "name": "springCloudClientHostInfo",
               "properties": {}
           }, {
               "name": "applicationConfig: [classpath:/application.yml]",
               "properties": {}
           }, {
               "name": "applicationConfig: [classpath:/bootstrap.yml]",
               "properties": {}
           }, {
               "name": "springCloudDefaultProperties",
               "properties": {}
           }
       ]
   }

   由此可见自定义的bootstrap的优先级比较高

   By default, bootstrap properties (not bootstrap.properties but properties that are loaded during the bootstrap phase) are added with high precedence, so they cannot be overridden by local configuration.
   默认情况下，bootstrap配置（不包含bootstrap.properties信息）信息具有高优先级，本地配置无法进行覆盖

   Because of the ordering rules of property sources, the “bootstrap” entries take precedence.
   However, note that these do not contain any data from bootstrap.yml, which has very low
   precedence but can be used to set defaults.

   由于配置资源的排序规则，bootstrap具有高优先级。但是，不包含bootstrap.yml配置文件的任何数据，默认情况下具有最低优先级

加载类

• 自定义bootstrap配置加载类PropertySourceBootstrapConfiguration ，自定义PropertySourceLocator排在最前

• 配置文件加载类ConfigFileApplicationListener,优先级为第11位

• BootstrapApplicationListener bootstrap配置，优先级为第6位

配置项

• bootstrap配置文件名称spring.cloud.bootstrap.name,默认为bootstrap
• bootstrap配置文件路径spring.cloud.bootstrap.location,默认为空
• spring.cloud.config.allowOverride=true 允许覆盖配置
• spring.cloud.config.overrideNone=false 外部化配置处于最低优先级并且不可覆盖
• spring.cloud.config.overrideSystemProperties=true 只有系统环境、命令行参数以及环境变量可以覆盖远程配置，其他的本地配置文件不可覆盖

spring.cloud.config配置类org.springframework.cloud.bootstrap.config.PropertySourceBootstrapProperties