Spring Cloud Context
2024-06-13 23:21:33
目录
概述
EnableAutoConfiguration
ApplicationListener
RestartListener
BootstrapApplicationListener
创建bootstrap context
BootstrapImportSelectorConfiguration
BootstrapImportSelector
BootstrapConfiguration
PropertySourceBootstrapConfiguration
PropertyPlaceholderAutoConfiguration
ConfigurationPropertiesRebinderAutoConfiguration
EncryptionBootstrapConfiguration
概述
Spring cloud context是用户ApplicationContext的父级上下文，称呼为BootstrapContext。根据springboot的加载机制，很多第三方以及重要的Configuration配置均是保存在了spring.factories文件中。
spring-cloud-context模块下的对应文件如下：
# AutoConfiguration
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration,\
org.springframework.cloud.autoconfigure.LifecycleMvcEndpointAutoConfiguration,\
org.springframework.cloud.autoconfigure.RefreshAutoConfiguration,\
org.springframework.cloud.autoconfigure.RefreshEndpointAutoConfiguration,\
org.springframework.cloud.autoconfigure.WritableEnvironmentEndpointAutoConfiguration
# Application Listeners
org.springframework.context.ApplicationListener=\
org.springframework.cloud.bootstrap.BootstrapApplicationListener,\
org.springframework.cloud.bootstrap.LoggingSystemShutdownListener,\
org.springframework.cloud.context.restart.RestartListener
# Bootstrap components
org.springframework.cloud.bootstrap.BootstrapConfiguration=\
org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration,\
org.springframework.cloud.bootstrap.encrypt.EncryptionBootstrapConfiguration,\
org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration,\
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration主要包含：
- EnableAutoConfiguration
- ApplicationListener
- BootstrapConfiguration
EnableAutoConfiguration
ApplicationListener
RestartListener
重启监听器，用于刷新上下文的。
@Overridepublic void onApplicationEvent(ApplicationEvent input) {if (input instanceof ApplicationPreparedEvent) {this.event = (ApplicationPreparedEvent) input;if (this.context == null) {this.context = this.event.getApplicationContext();}}// 上下文刷新结束事件，重新广播ApplicationPreparedEvent事件else if (input instanceof ContextRefreshedEvent) {if (this.context != null && input.getSource().equals(this.context)&& this.event != null) {this.context.publishEvent(this.event);}}else {if (this.context != null && input.getSource().equals(this.context)) {this.context = null;this.event = null;}}}BootstrapApplicationListener
public class BootstrapApplicationListenerimplements ApplicationListener<ApplicationEnvironmentPreparedEvent>, Ordered {/*** bootstrap 名称.*/public static final String BOOTSTRAP_PROPERTY_SOURCE_NAME = "bootstrap";/***顺序*/public static final int DEFAULT_ORDER = Ordered.HIGHEST_PRECEDENCE + 5;/*** 默认属性.*/public static final String DEFAULT_PROPERTIES = "springCloudDefaultProperties";private int order = DEFAULT_ORDER;
} 用于响应ApplicationEnvironmentPreparedEvent，表明BootstrapContext的加载时机在Application context之前，且其加载顺序比ConfigFileApplicationListener超前。
@Overridepublic void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {// 获取环境变量对象ConfigurableEnvironment environment = event.getEnvironment();// 读取spring.cloud.bootstrap.enabled环境属性，默认为true。可通过系统变量设置if (!environment.getProperty("spring.cloud.bootstrap.enabled", Boolean.class,true)) {return;}// don't listen to events in a bootstrap contextif (environment.getPropertySources().contains(BOOTSTRAP_PROPERTY_SOURCE_NAME)) {return;}// 寻找当前环境是否已存在BootstrapContextConfigurableApplicationContext context = null;String configName = environment.resolvePlaceholders("${spring.cloud.bootstrap.name:bootstrap}");for (ApplicationContextInitializer<?> initializer : event.getSpringApplication().getInitializers()) {if (initializer instanceof ParentContextApplicationContextInitializer) {context = findBootstrapContext((ParentContextApplicationContextInitializer) initializer,configName);}}// 如果还没有被创建，则开始创建if (context == null) {context = bootstrapServiceContext(environment, event.getSpringApplication(),configName);// 注册 CloseContextOnFailureApplicationListenerevent.getSpringApplication().addListeners(new CloseContextOnFailureApplicationListener(context));}// BootstrapContext上的beanType为ApplicationContextInitializer类型的bean对象集合会被注册至用户的Context上apply(context, event.getSpringApplication(), environment);}创建bootstrap context
private ConfigurableApplicationContext bootstrapServiceContext(ConfigurableEnvironment environment, final SpringApplication application,String configName) {//创建empty environmentStandardEnvironment bootstrapEnvironment = new StandardEnvironment();MutablePropertySources bootstrapProperties = bootstrapEnvironment.getPropertySources();for (PropertySource<?> source : bootstrapProperties) {bootstrapProperties.remove(source.getName());}// 读取spring.cloud.bootstrap.location属性，一般通过系统变量设置，默认为空String configLocation = environment.resolvePlaceholders("${spring.cloud.bootstrap.location:}");Map<String, Object> bootstrapMap = new HashMap<>();bootstrapMap.put("spring.config.name", configName);bootstrapMap.put("spring.main.web-application-type", "none");// 加载bootstrapContext配置文件的路径，与spring.config.name搭配使用if (StringUtils.hasText(configLocation)) {bootstrapMap.put("spring.config.location", configLocation);}bootstrapProperties.addFirst(new MapPropertySource(BOOTSTRAP_PROPERTY_SOURCE_NAME, bootstrapMap));把application context的 environment 的source 加入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()// 此处activeProfiles是通过系统变量设置的.profiles(environment.getActiveProfiles()).bannerMode(Mode.OFF)// 应用bootstrap本身的环境变量.environment(bootstrapEnvironment)// Don't use the default properties in this builder.registerShutdownHook(false).logStartupInfo(false).web(WebApplicationType.NONE);final SpringApplication builderApplication = builder.application();// 配置入口函数类if (builderApplication.getMainApplicationClass() == null) {builder.main(application.getMainApplicationClass());}if (environment.getPropertySources().contains("refreshArgs")) {builderApplication.setListeners(filterListeners(builderApplication.getListeners()));}// 增加入口类BootstrapImportSelectorConfigurationbuilder.sources(BootstrapImportSelectorConfiguration.class);final ConfigurableApplicationContext context = builder.run();
、// 设置bootstrapContext的别名为bootstrapcontext.setId("bootstrap");// 配置bootstrapContext为用户Context的父类addAncestorInitializer(application, context);// 合并defaultProperties对应的变量至childEnvironmentbootstrapProperties.remove(BOOTSTRAP_PROPERTY_SOURCE_NAME);mergeDefaultProperties(environment.getPropertySources(), bootstrapProperties);return context;
}BootstrapImportSelectorConfiguration
@Configuration(proxyBeanMethods = false)
@Import(BootstrapImportSelector.class)
public class BootstrapImportSelectorConfiguration {}导入了BootstrapImportSelector
BootstrapImportSelector
public String[] selectImports(AnnotationMetadata annotationMetadata) {ClassLoader classLoader = Thread.currentThread().getContextClassLoader();// 加载 BootstrapConfiguration 对应的factoriesList<String> names = new ArrayList<>(SpringFactoriesLoader.loadFactoryNames(BootstrapConfiguration.class, classLoader));// 加载 spring.cloud.bootstrap.sources 设置的类names.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(this.environment.getProperty("spring.cloud.bootstrap.sources", ""))));List<OrderedAnnotatedElement> elements = new ArrayList<>();for (String name : names) {try {elements.add(new OrderedAnnotatedElement(this.metadataReaderFactory, name));}catch (IOException e) {continue;}}AnnotationAwareOrderComparator.sort(elements);String[] classNames = elements.stream().map(e -> e.name).toArray(String[]::new);return classNames;
}上述的代码会去加载classpath路径下所有spring.factories文件中以org.springframework.cloud.bootstrap.BootstrapConfiguration作为Key的所有类；同时springcloud也支持通过设置spring.cloud.bootstrap.sources属性来加载指定类
spring.factories内容：
# Bootstrap components org.springframework.cloud.bootstrap.BootstrapConfiguration=\ org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration,\ org.springframework.cloud.bootstrap.encrypt.EncryptionBootstrapConfiguration,\ org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration,\ org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration
BootstrapConfiguration
PropertySourceBootstrapConfiguration
配置源的加载，此Configuration主要用于确定是否外部加载的配置属性复写Spring内含的环境变量。注意其是ApplicationContextInitializer接口的实现类，前文已经提到，bootstrapContext上的此接口的bean类都会被注册至子级的SpringApplication对象上。
PropertyPlaceholderAutoConfiguration
ConfigurationPropertiesRebinderAutoConfiguration
@Configuration
@ConditionalOnBean(ConfigurationPropertiesBindingPostProcessor.class)
public class ConfigurationPropertiesRebinderAutoConfigurationimplements ApplicationContextAware, SmartInitializingSingleton {
}EncryptionBootstrapConfiguration
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