Spring Cloud 覆写远端的配置属性实例详解

spring:
cloud:
config:
allowOverride: true
overrideNone: true
overrideSystemProperties: false

SpringApplicationBuilder.run() -> SpringApplication.run() -> SpringApplication.createAndRefreshContext() -> SpringApplication.applyInitializers() -> PropertySourceBootstrapConfiguration.initialize()
PropertySourceBootstrapConfiguration

public class PropertySourceBootstrapConfigurationimplements
 ApplicationContextInitializer<ConfigurableApplicationContext>, Ordered {
 private int order = Ordered.HIGHEST_PRECEDENCE + 10;
 @Autowired(required = false)
 private List<PropertySourceLocator> propertySourceLocators = new ArrayList<>();
 @Override
 public void initialize(ConfigurableApplicationContext applicationContext){
 CompositePropertySource composite = new CompositePropertySource(
 BOOTSTRAP_PROPERTY_SOURCE_NAME);
 //对propertySourceLocators数组进行排序，根据默认的AnnotationAwareOrderComparator
 AnnotationAwareOrderComparator.sort(this.propertySourceLocators);
 boolean empty = true;
 //获取运行的环境上下文
 ConfigurableEnvironment environment = applicationContext.getEnvironment();
 for (PropertySourceLocator locator : this.propertySourceLocators) {
 //遍历this.propertySourceLocators
 PropertySource<?> source = null;
 source = locator.locate(environment);
 if (source == null) {
 continue;
 }
 logger.info("Located property source: " + source);
 //将source添加到PropertySource的链表中
 composite.addPropertySource(source);
 empty = false;
 }
 //只有source不为空的情况，才会设置到environment中
 if (!empty) {
 //返回Environment的可变形式，可进行的操作如addFirst、addLast
 MutablePropertySources propertySources = environment.getPropertySources();
 String logConfig = environment.resolvePlaceholders("${logging.config:}");
 LogFile logFile = LogFile.get(environment);
 if (propertySources.contains(BOOTSTRAP_PROPERTY_SOURCE_NAME)) {
 //移除bootstrapProperties
 propertySources.remove(BOOTSTRAP_PROPERTY_SOURCE_NAME);
 }
 //根据config server覆写的规则，设置propertySources
 insertPropertySources(propertySources, composite);
 reinitializeLoggingSystem(environment, logConfig, logFile);
 setLogLevels(environment);
 //处理多个active profiles的配置信息
 handleIncludedProfiles(environment);
 }
 }
 //...
}

private void insertPropertySources(MutablePropertySources propertySources,
 CompositePropertySource composite) {
 MutablePropertySources incoming = new MutablePropertySources();
 incoming.addFirst(composite);
 PropertySourceBootstrapProperties remoteProperties = new PropertySourceBootstrapProperties();
 new RelaxedDataBinder(remoteProperties, "spring.cloud.config")
 .bind(new PropertySourcesPropertyValues(incoming));
 //如果不允许本地覆写
 if (!remoteProperties.isAllowOverride() || (!remoteProperties.isOverrideNone()
 && remoteProperties.isOverrideSystemProperties())) {
 propertySources.addFirst(composite);
 return;
 }
 //overrideNone为true，外部配置优先级最低
 if (remoteProperties.isOverrideNone()) {
 propertySources.addLast(composite);
 return;
 }
 if (propertySources
 .contains(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME)) {
 //根据overrideSystemProperties，设置外部配置的优先级
 if (!remoteProperties.isOverrideSystemProperties()) {
 propertySources.addAfter(
  StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,
  composite);
 }
 else {
 propertySources.addBefore(
  StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,
  composite);
 }
 }
 else {
 propertySources.addLast(composite);
 }
}

@Autowired(required = false)
 private PropertySourceBootstrapProperties remotePropertiesForOverriding;
 @Override
 public int getOrder(){
 return this.order;
 private void insertPropertySources(MutablePropertySources propertySources,
 CompositePropertySource composite) {
 MutablePropertySources incoming = new MutablePropertySources();
 incoming.addFirst(composite);
 PropertySourceBootstrapProperties remoteProperties = remotePropertiesForOverriding == null
 ? new PropertySourceBootstrapProperties()
 : remotePropertiesForOverriding;