Spring Boot 外部化配置参数变量优先级覆盖配置参数

阳光穿透心脏的1/2处 2022-12-29 14:25 296阅读 0赞

# 前言 #

本文介绍SpringBoot常用外部化配置方法，其中优先级数值越高，优先级越大，会覆盖优先级底的配置

# 配置文件方式（优先级3） #

boostrap.yml内指定spring.cloud.nacos.config.server-addr参数参考如下：

spring:
      application:
        name: service-a
      cloud:
        nacos:
          config:
            server-addr: 127.0.0.1:8848
            file-extension: yml
          discovery:
            server-addr: 127.0.0.1:8848

项目打包

target/service-a-0.0.1-SNAPSHOT.jar

# Java系统属性方式（优先级6） #

java -jar target/service-a-0.0.1-SNAPSHOT.jar -Dspring.cloud.nacos.config.server-addr=127.0.0.2:8848

# 命令行参数方式（优先级11） #

java -jar target/service-a-0.0.1-SNAPSHOT.jar --spring.cloud.nacos.config.server-addr=127.0.0.3:8848

# 系统环境变量参数方式（优先级5） #

export SPRING_CLOUD_NACOS_CONFIG_SERVERADDR=127.0.0.4:8848
    java -jar target/service-a-0.0.1-SNAPSHOT.jar

**注意**：环境变量同意采用大写字母，不允许使用.-符号，采用下划线“\_”取代点“.”  减号“-”直接删除。

说明：系统环境变量方式自由度高，可配合k8s部署脚本，动态切换到各运行环境

参考如下：

kind: Deployment
    apiVersion: apps/v1
    metadata:
      name: service-a
    spec:
      template:
        spec:      
          containers:
            - name: service-a
              env:
                - name: SPRING_PROFILES_ACTIVE
                  value: prod
                - name: JAVA_OPTIONS
                  value: '-XX:MaxRAMFraction=2'
                - name: SPRING_CLOUD_NACOS_CONFIG_SERVERADDR
                  value: '10.0.0.2:8848'            
                - name: SPRING_CLOUD_NACOS_DISCOVERY_SERVERADDR
                  value: '10.0.0.2:8848'

# 加载顺序、优先级参考 #

Spring Boot uses a very particular PropertySource order that is designed to allow sensible  
overriding of values. Properties are considered in the following order (with values from lower  
items overriding earlier ones):  
1. Default properties (specified by setting SpringApplication.setDefaultProperties).  
2. @PropertySource annotations on your @Configuration classes. Please note that such property  
sources are not added to the Environment until the application context is being refreshed. This is  
too late to configure certain properties such as logging.\* and spring.main.\* which are read  
before refresh begins.  
3. Config data (such as application.properties files)  
4. A RandomValuePropertySource that has properties only in random.\*.  
5. OS environment variables.  
6. Java System properties (System.getProperties()).  
7. JNDI attributes from java:comp/env.  
8. ServletContext init parameters.  
9. ServletConfig init parameters.  
10. Properties from SPRING\_APPLICATION\_JSON (inline JSON embedded in an environment variable or  
system property).  
11. Command line arguments.  
12. properties attribute on your tests. Available on @SpringBootTest and the test annotations for  
54testing a particular slice of your application.  
13. @TestPropertySource annotations on your tests.  
14. Devtools global settings properties in the $HOME/.config/spring-boot directory when devtools is  
active.