Mflyyou

# SpringBoot 属性配置

# 配置文件加载顺序

  1. Command line arguments. （--name="Spring"）
  2. Java System properties (System.getProperties()). （Java -D 指定的和一些默认的 java 配置有关的属性）
  3. OS environment variables.
  4. Config data (such as application.properties files).
  5. @PropertySource (opens new window) annotations on your @Configuration classes. Please note that such property sources are not added to the Environment until the application context is being refreshed.
  6. Default properties (specified by setting SpringApplication.setDefaultProperties).

Config data

  1. From the classpath
    1. The classpath root
    2. The classpath /config package
  2. From the current directory
    1. The current directory
    2. The config/ subdirectory in the current directory
    3. Immediate child directories of the config/ subdirectory

spring.config.import

spring.config.import 和声明的位置有关，它会比声明的位置的配置优先级高。

# 指定文件以 yaml 解析
spring.config.import=file:/etc/config/myconfig[.yaml]

# application.properties
spring.application.name=myapp
spring.config.import=optional:file:./dev.properties

dev.properties 比 application.properties 优先级高。

Directly Loading YAML

Spring Framework provides two convenient classes that can be used to load YAML documents. The YamlPropertiesFactoryBean loads YAML as Properties and the YamlMapFactoryBean loads YAML as a Map.

You can also use the YamlPropertySourceLoader class if you want to load YAML as a Spring PropertySource.

Binding From Environment Variables

SpringBoot 为了将系统环境变量的值对应到配置文件，它会做一个转换。

  • Replace dots (.) with underscores (_).
  • Remove any dashes (-).
  • Convert to uppercase.

比如配置 spring.profiles.active 对应的环境变量就是 SPRING_PROFILES.ACTIVE

TIP

推荐使用全小写字母，- 隔开单词进行，配置属性定义。

# 通用配置提取

有的时候我们需要屏蔽不必要的技术细节和复杂度传递，比如 sleuth ，zipkin，actuator ，数据库连接池 等配置，开发的注意力应该较多集中在业务上。

同时又需要提供可以覆写的自由度，比如公共库中配置了 server.max-http-header-size: 10KB ，但有的项目也可以修改为 50KB。

Spring 的配置属性由 Environment 统一管理，同时针对不同配置的来源抽象了PropertySource ，当需要查找某个属性时，根据配置的优先级从 PropertySource 查找，找到就返回。

我们常用到的配置加载顺序

  1. Command line arguments
  2. Java System properties
  3. ./file:/config/application-{profile}.yml
  4. ./file:/application-{profile}.yml
  5. ./file:/config/application.yml6
  6. ./file:/application.yml5
  7. classpath:/config/application-{profile}.yml
  8. classpath:/application-{profile}.yml
  9. classpath:/config/application.yml
  10. classpath:/application.yml

我们可以实现 EnvironmentPostProcessor 添加一些 PropertySource 到 Environmen 中去。

  1. classpath:/application-default-{profile}.yml
  2. classpath:/application-default.yml

代码预览 ApplicationDefaultEnvironmentPostProcessor (opens new window)

然后在 META-INF/spring.factories 配置让 SpringBoot 的 SPI 去加载我们的实现

org.springframework.boot.env.EnvironmentPostProcessor=\
    com.mflyyou.cloud.common.env.ApplicationDefaultEnvironmentPostProcessor

# 配置属性使用

自动化配置 starter 中定义

@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(SomeProperties.class)
public class MyConfiguration {

}
@ConfigurationProperties("some.properties")
public class SomeProperties {

}

从 springboot Environment 中注册 bean。

@Configuration(proxyBeanMethods = false)
public class ThirdPartyConfiguration {

    @Bean
    @ConfigurationProperties(prefix = "another")
    public AnotherComponent anotherComponent() {
        return new AnotherComponent();
    }

}

# 热更新配置

只有引入org.springframework.cloud:spring-cloud-starter-bootstrap。在 bootstrap.yaml 配置的属性，才可以通过 /actuator/refresh 刷新。

spring:
    config:
        import: classpath:secrets-mock.yaml
management:
    endpoints:
        web:
            exposure:
                include: "*"

curl -X POST localhost:8080/actuator/refresh

# Spring Cloud Kubernetes Configuration

Load application properties from Kubernetes ConfigMaps (opens new window) and Secrets (opens new window).

apiVersion: v1
kind: ConfigMap
metadata:
    name: { { include "application.fullname" . } }
    namespace: { { .Values.namespace } }
    labels:
        spring.cloud.kubernetes.config: "true"
data:
    application.yaml: |-
        spring:
          application:
            name: {{ include "application.fullname" . }}
          cloud:
              kubernetes:
                namespace: {{ .Values.namespace }} # 默认和 pod 同一个 namespace，可以不设置
                config:
                  sources:
                    - name: {{ include "application.fullname" . }}
                    - name: sample2
        {{- tpl (toYaml .Values.config) . | nindent 4 }}

# 会刷新对应 pod 的 environment
curl -X POST localhost:8080/actuator/refresh

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