Springboot集成Nacos后配置属性加载顺序问题

文章目录

结论

在项目中同时使用nacos加载配置属性和application.properties配置文件，默认情况下，先加载application.properties后加载nacos的配置文件，读取属性是先读取application.propeties，没找到才会读取nacos的配置。

分析

1. 加载application.properties

org.springframework.boot.context.config.ConfigFileApplicationListener

2. 加载nacos属性

1. 获取nacos属性

com.alibaba.nacos.spring.core.env.AbstractNacosPropertySourceBuilder#doBuild

String nacosConfig = nacosConfigLoader.load(dataId, groupId, nacosProperties);

2. 添加NacosPropertySource

com.alibaba.nacos.spring.core.env.NacosPropertySourcePostProcessor#addNacosPropertySource

privatevoidaddNacosPropertySource(NacosPropertySource nacosPropertySource){MutablePropertySources propertySources = environment.getPropertySources();boolean first = nacosPropertySource.isFirst();String before = nacosPropertySource.getBefore();String after = nacosPropertySource.getAfter();boolean hasBefore =!nullSafeEquals(DEFAULT_STRING_ATTRIBUTE_VALUE, before);boolean hasAfter =!nullSafeEquals(DEFAULT_STRING_ATTRIBUTE_VALUE, after);boolean isRelative = hasBefore || hasAfter;if(first){// If First
      propertySources.addFirst(nacosPropertySource);}elseif(isRelative){// If relativeif(hasBefore){
         propertySources.addBefore(before, nacosPropertySource);}if(hasAfter){
         propertySources.addAfter(after, nacosPropertySource);}}else{
      propertySources.addLast(nacosPropertySource);// default add last}}

3. spring的所有环境属性列表

org.springframework.core.env.MutablePropertySources#propertySourceList

1. propertySourceList示例图

4. 获取属性

1. applicationContext.getEnvironment().getProperty()

2. @Value注入属性

org.springframework.beans.factory.support.DefaultListableBeanFactory#doResolveDependency

Class<?> type = descriptor.getDependencyType();Object value =getAutowireCandidateResolver().getSuggestedValue(descriptor);if(value !=null){if(value instanceofString){String strVal =resolveEmbeddedValue((String) value);BeanDefinition bd =(beanName !=null&&containsBean(beanName)?getMergedBeanDefinition(beanName):null);
      value =evaluateBeanDefinitionString(strVal, bd);}TypeConverter converter =(typeConverter !=null? typeConverter :getTypeConverter());try{return converter.convertIfNecessary(value, type, descriptor.getTypeDescriptor());}catch(UnsupportedOperationException ex){// A custom TypeConverter which does not support TypeDescriptor resolution...return(descriptor.getField()!=null?
            converter.convertIfNecessary(value, type, descriptor.getField()):
            converter.convertIfNecessary(value, type, descriptor.getMethodParameter()));}}

两种方式最后是相同的获取属性的方法，org.springframework.core.env.PropertyResolver#getProperty(java.lang.String)，按照PropertySourceList循环取，取到即跳出循环

@Nullableprotected<T>TgetProperty(String key,Class<T> targetValueType,boolean resolveNestedPlaceholders){if(this.propertySources !=null){for(PropertySource<?> propertySource :this.propertySources){if(logger.isTraceEnabled()){
            logger.trace("Searching for key '"+ key +"' in PropertySource '"+
                  propertySource.getName()+"'");}Object value = propertySource.getProperty(key);if(value !=null){if(resolveNestedPlaceholders && value instanceofString){
               value =resolveNestedPlaceholders((String) value);}logKeyFound(key, propertySource, value);returnconvertValueIfNecessary(value, targetValueType);}}}if(logger.isTraceEnabled()){
      logger.trace("Could not find key '"+ key +"' in any property source");}returnnull;}