應用的配置源一般都是遠端的Config Server服務器,默認狀況下,本地的配置優先級低於遠端配置倉庫。若是想實現本地應用的系統變量和config文件覆蓋遠端倉庫中的屬性值,能夠經過以下設置:html
spring:
cloud:
config:
allowOverride: true
overrideNone: true
overrideSystemProperties: false
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客戶端經過如上配置,能夠實現本地配置優先級更高,且不能被覆蓋。因爲咱們基於的Spring Cloud當前版本是Edgware.RELEASE
,上面的設置並不能起做用,而是使用了PropertySourceBootstrapProperties
中的默認值。具體狀況見issue:https://github.com/spring-cloud/spring-cloud-commons/pull/250
,咱們在下面分析時會講到具體的bug源。java
覆寫遠端的配置屬性歸根結底與客戶端的啓動時獲取配置有關,在獲取到配置以後如何處理?咱們看一下spring cloud config中的資源獲取類ConfigServicePropertySourceLocator
的類圖。git
ConfigServicePropertySourceLocator
實質是一個屬性資源定位器,其主要方法是locate(Environment environment)
。首先用當前運行應用的環境的application、profile和label替換configClientProperties中的佔位符並初始化RestTemplate,而後遍歷labels數組直到獲取到有效的配置信息,最後還會根據是否快速失敗進行重試。主要流程以下:github
locate(Environment environment)
調用getRemoteEnvironment(restTemplate, properties, label, state)
方法經過http的方式獲取遠程服務器上的配置數據。實現也很簡單,顯示替換請求路徑path中佔位符,而後進行頭部headers組裝,組裝好了就能夠發送請求,最後返回結果。 在上面的實現中,咱們看到獲取到的配置信息存放在CompositePropertySource
,那是如何使用它的呢?這邊補充另外一個重要的類是PropertySourceBootstrapConfiguration,它實現了ApplicationContextInitializer接口,該接口會在應用上下文刷新以前refresh()
被回調,從而執行初始化操做,應用啓動後的調用棧以下:spring
SpringApplicationBuilder.run() -> SpringApplication.run() -> SpringApplication.createAndRefreshContext() -> SpringApplication.applyInitializers() -> PropertySourceBootstrapConfiguration.initialize()
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而上述ConfigServicePropertySourceLocator
的locate方法會在initialize中被調用,從而保證上下文在刷新以前可以拿到必要的配置信息。具體看一下initialize方法:bootstrap
public class PropertySourceBootstrapConfiguration implements 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);
//對propertySourceLocators數組進行排序,根據默認的AnnotationAwareOrderComparator
AnnotationAwareOrderComparator.sort(this.propertySourceLocators);
boolean empty = true;
//獲取運行的環境上下文
ConfigurableEnvironment environment = applicationContext.getEnvironment();
for (PropertySourceLocator locator : this.propertySourceLocators) {
//遍歷this.propertySourceLocators
PropertySource<?> source = null;
source = locator.locate(environment);
if (source == null) {
continue;
}
logger.info("Located property source: " + source);
//將source添加到PropertySource的鏈表中
composite.addPropertySource(source);
empty = false;
}
//只有source不爲空的狀況,纔會設置到environment中
if (!empty) {
//返回Environment的可變形式,可進行的操做如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);
}
//根據config server覆寫的規則,設置propertySources
insertPropertySources(propertySources, composite);
reinitializeLoggingSystem(environment, logConfig, logFile);
setLogLevels(environment);
//處理多個active profiles的配置信息
handleIncludedProfiles(environment);
}
}
//...
}
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下面咱們看一下,在initialize
方法中進行了哪些操做。數組
初始化方法initialize
處理時,先將全部PropertySourceLocator類型的對象的locate
方法遍歷,而後將各類方式獲得的屬性值放到CompositePropertySource中,最後調用insertPropertySources(propertySources, composite)
方法設置到Environment中。Spring Cloud Context中提供了覆寫遠端屬性的PropertySourceBootstrapProperties
,利用該配置類進行判斷屬性源的優先級。bash
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));
//若是不容許本地覆寫
if (!remoteProperties.isAllowOverride() || (!remoteProperties.isOverrideNone()
&& remoteProperties.isOverrideSystemProperties())) {
propertySources.addFirst(composite);
return;
}
//overrideNone爲true,外部配置優先級最低
if (remoteProperties.isOverrideNone()) {
propertySources.addLast(composite);
return;
}
if (propertySources
.contains(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME)) {
//根據overrideSystemProperties,設置外部配置的優先級
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);
}
}
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上述實現主要是根據PropertySourceBootstrapProperties
中的屬性,調整多個配置源的優先級。從其實現能夠看到 PropertySourceBootstrapProperties
對象的是被直接初始化,使用的是默認的屬性值而並未注入咱們在配置文件中設置的。服務器
修復後的實現:微信
@Autowired(required = false)
private PropertySourceBootstrapProperties remotePropertiesForOverriding;
private void insertPropertySources(MutablePropertySources propertySources, CompositePropertySource composite) {
MutablePropertySources incoming = new MutablePropertySources();
incoming.addFirst(composite);
PropertySourceBootstrapProperties remoteProperties = remotePropertiesForOverriding == null ? new PropertySourceBootstrapProperties() : remotePropertiesForOverriding;
...
}
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