SpringBoot配置文件加载顺序与参数优先级详解

场景背景

在现代微服务架构中，配置管理是确保应用在不同环境中正确运行的关键环节。Spring Boot提供了强大而灵活的配置机制，但复杂的配置源和优先级规则常常让开发者困惑。本文通过实际运行和日志分析，深入解析Spring Boot配置加载机制，帮助开发者掌握配置文件加载顺序和参数优先级。

⚠️ 本文基于 Spring Boot 2.7.0（ConfigFileApplicationListener 模型）进行实验验证。
Spring Boot 2.4+ 起引入 ConfigData 机制，虽然总体原则一致，但内部加载流程有所不同。

本次实验代码如下：demo-sprintboot.zip

术语说明

在开始之前，我们先明确两个核心概念：

• 配置控制参数：用于控制配置加载行为的参数，如 --spring.profiles.active、--spring.config.location
• 属性值参数：用于直接提供属性值的参数，如 --app.description="命令行参数"、-Dapp.description="JVM系统属性"

配置加载机制概述

Spring Boot配置处理分为两个阶段：

配置加载阶段

在配置加载阶段，Spring Boot根据命令行参数确定需要加载哪些配置文件。

例如：当使用命令行参数--spring.profiles.active=prod时，Spring Boot会在配置加载阶段确定需要加载application-prod.yml配置文件。

属性解析阶段

在属性解析阶段，Spring Boot按照优先级顺序解析每个属性的最终值。

例如：当同时存在命令行参数--app.description="命令行参数"和配置文件中的app.description: "配置文件值"时，Spring Boot会在属性解析阶段选择命令行参数的值作为最终值。

一、外部配置属性源优先级顺序

Spring Boot使用一个特定的PropertySource顺序，旨在允许合理地覆盖值。属性按以下顺序考虑（优先级从低到高）：

1. 默认属性（通过SpringApplication.setDefaultProperties指定）
2. @PropertySource注解在@Configuration类上定义的属性
3. 配置数据文件（如application.properties等）
4. RandomValuePropertySource，只包含random.*属性
5. 操作系统环境变量
6. Java系统属性（System.getProperties()）
7. 来自java:comp/env的JNDI属性
8. ServletContext初始化参数
9. ServletConfig初始化参数
10. SPRING_APPLICATION_JSON中的属性（环境变量或系统属性中内嵌的JSON）
11. 命令行参数
12. 测试属性（@SpringBootTest#properties属性等）

二、配置文件加载顺序与优先级

在配置文件加载方面，Spring Boot遵循特定的搜索顺序和优先级规则。

配置文件搜索位置

Spring Boot按以下顺序搜索配置文件（从高优先级到低优先级）：

1. 当前目录下的/config子目录（外部配置）
2. 当前目录（外部配置）
3. classpath下的/config包（内部配置）
4. classpath根目录（内部配置）

这意味着外部配置文件（位于jar包外部）优先级高于内部配置文件（位于jar包内部）。

同一目录下不同格式配置文件的处理

在同一目录下，Spring Boot会加载所有格式的配置文件（.properties、.yml、.yaml），但它们的优先级如下：

1. .properties（最高优先级）
2. .yml
3. .yaml（最低优先级）

这表示如果同一目录下同时存在application.properties、application.yml、application.yaml文件，它们都会被加载，但同名属性在application.properties中的值会覆盖其他文件中的值。

关键点

• 由--spring.profiles.active等参数控制加载内容
• 外部配置文件优先级高于jar包内配置文件
• 同一目录下config目录优先于根目录
• 同一目录下不同格式配置文件优先级：.properties > .yml > .yaml

实验一：验证默认加载顺序

java -Dfile.encoding=UTF-8 -jar demo-1.0-SAPSHOT.jar

输出结果：

==============================================
Spring Boot配置文件加载顺序与优先级演示
==============================================
配置属性源列表（按加载顺序显示）:
 1. Config resource 'class path resource [application.yaml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yaml"
 2. Config resource 'class path resource [application.yml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yml"
 3. Config resource 'class path resource [application.properties]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.properties"
 4. Config resource 'class path resource [config/application.yaml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yaml"
 5. Config resource 'class path resource [config/application.yml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yml"
 6. Config resource 'class path resource [config/application.properties]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.properties"
 7. Config resource 'file [application.yaml]' via location 'optional:file:./' => app.description: "外部根目录application.yaml"
 8. Config resource 'file [application.yml]' via location 'optional:file:./' => app.description: "外部根目录application.yml"
 9. Config resource 'file [application.properties]' via location 'optional:file:./' => app.description: "外部根目录application.properties"
10. Config resource 'file [config\application.yaml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yaml"
11. Config resource 'file [config\application.yml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yml"
12. Config resource 'file [config\application.properties]' via location 'optional:file:./config/' => app.description: "外部config目录application.properties"
13. random                                             => app.description: null
14. systemEnvironment                                  => app.description: null
15. systemProperties                                   => app.description: null
16. servletContextInitParams                           => app.description: null
17. servletConfigInitParams                            => app.description: null
==============================================
配置属性源列表（按优先级从高到低）:
 1. servletConfigInitParams                            => app.description: null
 2. servletContextInitParams                           => app.description: null
 3. systemProperties                                   => app.description: null
 4. systemEnvironment                                  => app.description: null
 5. random                                             => app.description: null
 6. Config resource 'file [config\application.properties]' via location 'optional:file:./config/' => app.description: "外部config目录application.properties"
 7. Config resource 'file [config\application.yml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yml"
 8. Config resource 'file [config\application.yaml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yaml"
 9. Config resource 'file [application.properties]' via location 'optional:file:./' => app.description: "外部根目录application.properties"
10. Config resource 'file [application.yml]' via location 'optional:file:./' => app.description: "外部根目录application.yml"
11. Config resource 'file [application.yaml]' via location 'optional:file:./' => app.description: "外部根目录application.yaml"
12. Config resource 'class path resource [config/application.properties]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.properties"
13. Config resource 'class path resource [config/application.yml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yml"
14. Config resource 'class path resource [config/application.yaml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yaml"
15. Config resource 'class path resource [application.properties]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.properties"
16. Config resource 'class path resource [application.yml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yml"
17. Config resource 'class path resource [application.yaml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yaml"
==============================================
最终生效的app.description值: 外部config目录application.properties
==============================================

结论：jar包内的配置文件先被加载，但外部配置文件具有更高的优先级。同级目录下config目录优先于根目录。

实验二：验证 Profile 特定加载

java -Dfile.encoding=UTF-8 -jar demo-1.0-SNAPSHOT.jar --spring.profiles.active=prod

输出结果：

==============================================
Spring Boot配置文件加载顺序与优先级演示
==============================================
配置属性源列表（按加载顺序显示）:
 1. Config resource 'class path resource [application.yaml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yaml"
 2. Config resource 'class path resource [application.yml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yml"
 3. Config resource 'class path resource [application.properties]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.properties"
 4. Config resource 'class path resource [config/application.yaml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yaml"
 5. Config resource 'class path resource [config/application.yml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yml"
 6. Config resource 'class path resource [config/application.properties]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.properties"
 7. Config resource 'class path resource [application-prod.yaml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application-prod.yaml"
 8. Config resource 'class path resource [application-prod.yml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application-prod.yml"
 9. Config resource 'class path resource [application-prod.properties]' via location 'optional:classpath:/' => app.description: "jar包内根目录application-prod.properties"
10. Config resource 'class path resource [config/application-prod.yaml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application-prod.yaml"
11. Config resource 'class path resource [config/application-prod.yml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application-prod.yml"
12. Config resource 'class path resource [config/application-prod.properties]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application-prod.properties"
13. Config resource 'file [application.yaml]' via location 'optional:file:./' => app.description: "外部根目录application.yaml"
14. Config resource 'file [application.yml]' via location 'optional:file:./' => app.description: "外部根目录application.yml"
15. Config resource 'file [application.properties]' via location 'optional:file:./' => app.description: "外部根目录application.properties"
16. Config resource 'file [config\application.yaml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yaml"
17. Config resource 'file [config\application.yml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yml"
18. Config resource 'file [config\application.properties]' via location 'optional:file:./config/' => app.description: "外部config目录application.properties"
19. Config resource 'file [application-prod.yaml]' via location 'optional:file:./' => app.description: "外部根目录application-prod.yaml"
20. Config resource 'file [application-prod.yml]' via location 'optional:file:./' => app.description: "外部根目录application-prod.yml"
21. Config resource 'file [application-prod.properties]' via location 'optional:file:./' => app.description: "外部根目录application-prod.properties"
22. Config resource 'file [config\application-prod.yaml]' via location 'optional:file:./config/' => app.description: "外部config目录application-prod.yaml"
23. Config resource 'file [config\application-prod.yml]' via location 'optional:file:./config/' => app.description: "外部config目录application-prod.yml"
24. Config resource 'file [config\application-prod.properties]' via location 'optional:file:./config/' => app.description: "外部config目录application-prod.properties"
25. random                                             => app.description: null
26. systemEnvironment                                  => app.description: null
27. systemProperties                                   => app.description: null
28. servletContextInitParams                           => app.description: null
29. servletConfigInitParams                            => app.description: null
30. commandLineArgs                                    => app.description: null
==============================================
配置属性源列表（按优先级从高到低）:
 1. commandLineArgs                                    => app.description: null
 2. servletConfigInitParams                            => app.description: null
 3. servletContextInitParams                           => app.description: null
 4. systemProperties                                   => app.description: null
 5. systemEnvironment                                  => app.description: null
 6. random                                             => app.description: null
 7. Config resource 'file [config\application-prod.properties]' via location 'optional:file:./config/' => app.description: "外部config目录application-prod.properties"
 8. Config resource 'file [config\application-prod.yml]' via location 'optional:file:./config/' => app.description: "外部config目录application-prod.yml"
 9. Config resource 'file [config\application-prod.yaml]' via location 'optional:file:./config/' => app.description: "外部config目录application-prod.yaml"
10. Config resource 'file [application-prod.properties]' via location 'optional:file:./' => app.description: "外部根目录application-prod.properties"
11. Config resource 'file [application-prod.yml]' via location 'optional:file:./' => app.description: "外部根目录application-prod.yml"
12. Config resource 'file [application-prod.yaml]' via location 'optional:file:./' => app.description: "外部根目录application-prod.yaml"
13. Config resource 'file [config\application.properties]' via location 'optional:file:./config/' => app.description: "外部config目录application.properties"
14. Config resource 'file [config\application.yml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yml"
15. Config resource 'file [config\application.yaml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yaml"
16. Config resource 'file [application.properties]' via location 'optional:file:./' => app.description: "外部根目录application.properties"
17. Config resource 'file [application.yml]' via location 'optional:file:./' => app.description: "外部根目录application.yml"
18. Config resource 'file [application.yaml]' via location 'optional:file:./' => app.description: "外部根目录application.yaml"
19. Config resource 'class path resource [config/application-prod.properties]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application-prod.properties"
20. Config resource 'class path resource [config/application-prod.yml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application-prod.yml"
21. Config resource 'class path resource [config/application-prod.yaml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application-prod.yaml"
22. Config resource 'class path resource [application-prod.properties]' via location 'optional:classpath:/' => app.description: "jar包内根目录application-prod.properties"
23. Config resource 'class path resource [application-prod.yml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application-prod.yml"
24. Config resource 'class path resource [application-prod.yaml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application-prod.yaml"
25. Config resource 'class path resource [config/application.properties]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.properties"
26. Config resource 'class path resource [config/application.yml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yml"
27. Config resource 'class path resource [config/application.yaml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yaml"
28. Config resource 'class path resource [application.properties]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.properties"
29. Config resource 'class path resource [application.yml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yml"
30. Config resource 'class path resource [application.yaml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yaml"
==============================================
最终生效的app.description值: 外部config目录application-prod.properties
==============================================

结论：

1. --spring.profiles.active=prod是配置控制参数
2. --spring.profiles.active=prod会触发加载所有位置的application-prod.yml配置文件
3. jar包内的配置文件先被加载，但外部配置文件具有更高的优先级
4. 同级目录下config目录优先于根目录

三、属性值参数优先级验证

实验三：命令行 vs JVM 参数 vs 环境变量

set APP_DESCRIPTION=demo-application-env && java -Dfile.encoding=UTF-8 -Dapp.description="JVM系统属性" \
-jar demo-1.0-SNAPSHOT.jar \
--app.description="应用程序的--命令行参数"

输出结果：

==============================================
Spring Boot配置文件加载顺序与优先级演示
==============================================
配置属性源列表（按加载顺序显示）:
 1. Config resource 'class path resource [application.yaml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yaml"
 2. Config resource 'class path resource [application.yml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yml"
 3. Config resource 'class path resource [application.properties]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.properties"
 4. Config resource 'class path resource [config/application.yaml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yaml"
 5. Config resource 'class path resource [config/application.yml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yml"
 6. Config resource 'class path resource [config/application.properties]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.properties"
 7. Config resource 'file [application.yaml]' via location 'optional:file:./' => app.description: "外部根目录application.yaml"
 8. Config resource 'file [application.yml]' via location 'optional:file:./' => app.description: "外部根目录application.yml"
 9. Config resource 'file [application.properties]' via location 'optional:file:./' => app.description: "外部根目录application.properties"
10. Config resource 'file [config\application.yaml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yaml"
11. Config resource 'file [config\application.yml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yml"
12. Config resource 'file [config\application.properties]' via location 'optional:file:./config/' => app.description: "外部config目录application.properties"
13. random                                             => app.description: null
14. systemEnvironment                                  => app.description: "demo-application-env "
15. systemProperties                                   => app.description: "JVM系统属性"
16. servletContextInitParams                           => app.description: null
17. servletConfigInitParams                            => app.description: null
18. commandLineArgs                                    => app.description: "应用程序的--命令行参数"
==============================================
配置属性源列表（按优先级从高到低）:
 1. commandLineArgs                                    => app.description: "应用程序的--命令行参数"
 2. servletConfigInitParams                            => app.description: null
 3. servletContextInitParams                           => app.description: null
 4. systemProperties                                   => app.description: "JVM系统属性"
 5. systemEnvironment                                  => app.description: "demo-application-env "
 6. random                                             => app.description: null
 7. Config resource 'file [config\application.properties]' via location 'optional:file:./config/' => app.description: "外部config目录application.properties"
 8. Config resource 'file [config\application.yml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yml"
 9. Config resource 'file [config\application.yaml]' via location 'optional:file:./config/' => app.description: "外部config目录application.yaml"
10. Config resource 'file [application.properties]' via location 'optional:file:./' => app.description: "外部根目录application.properties"
11. Config resource 'file [application.yml]' via location 'optional:file:./' => app.description: "外部根目录application.yml"
12. Config resource 'file [application.yaml]' via location 'optional:file:./' => app.description: "外部根目录application.yaml"
13. Config resource 'class path resource [config/application.properties]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.properties"
14. Config resource 'class path resource [config/application.yml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yml"
15. Config resource 'class path resource [config/application.yaml]' via location 'optional:classpath:/config/' => app.description: "jar包内config/application.yaml"
16. Config resource 'class path resource [application.properties]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.properties"
17. Config resource 'class path resource [application.yml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yml"
18. Config resource 'class path resource [application.yaml]' via location 'optional:classpath:/' => app.description: "jar包内根目录application.yaml"
==============================================
最终生效的app.description值: 应用程序的--命令行参数
==============================================

结论：命令行参数 > JVM系统属性(-D参数) > 环境变量，符合官方文档定义的优先级顺序。

实验四：自定义配置目录加载验证

java -Dfile.encoding=UTF-8 -Dapp.description="JVM系统属性" \
-jar demo-1.0-SNAPSHOT.jar \
--app.description="命令行参数" \
--spring.config.location=file:./config/ \
--spring.profiles.active=prod

输出结果：

==============================================
Spring Boot配置文件加载顺序与优先级演示
==============================================
配置属性源列表（按加载顺序显示）:
 1. Config resource 'file [config\application.yaml]' via location 'file:./config/' => app.description: "外部config目录application.yaml"
 2. Config resource 'file [config\application.yml]' via location 'file:./config/' => app.description: "外部config目录application.yml"
 3. Config resource 'file [config\application.properties]' via location 'file:./config/' => app.description: "外部config目录application.properties"
 4. Config resource 'file [config\application-prod.yaml]' via location 'file:./config/' => app.description: "外部config目录application-prod.yaml"
 5. Config resource 'file [config\application-prod.yml]' via location 'file:./config/' => app.description: "外部config目录application-prod.yml"
 6. Config resource 'file [config\application-prod.properties]' via location 'file:./config/' => app.description: "外部config目录application-prod.properties"
 7. random                                             => app.description: null
 8. systemEnvironment                                  => app.description: null
 9. systemProperties                                   => app.description: "JVM系统属性"
10. servletContextInitParams                           => app.description: null
11. servletConfigInitParams                            => app.description: null
12. commandLineArgs                                    => app.description: "命令行参数"
==============================================
配置属性源列表（按优先级从高到低）:
 1. commandLineArgs                                    => app.description: "命令行参数"
 2. servletConfigInitParams                            => app.description: null
 3. servletContextInitParams                           => app.description: null
 4. systemProperties                                   => app.description: "JVM系统属性"
 5. systemEnvironment                                  => app.description: null
 6. random                                             => app.description: null
 7. Config resource 'file [config\application-prod.properties]' via location 'file:./config/' => app.description: "外部config目录application-prod.properties"
 8. Config resource 'file [config\application-prod.yml]' via location 'file:./config/' => app.description: "外部config目录application-prod.yml"
 9. Config resource 'file [config\application-prod.yaml]' via location 'file:./config/' => app.description: "外部config目录application-prod.yaml"
10. Config resource 'file [config\application.properties]' via location 'file:./config/' => app.description: "外部config目录application.properties"
11. Config resource 'file [config\application.yml]' via location 'file:./config/' => app.description: "外部config目录application.yml"
12. Config resource 'file [config\application.yaml]' via location 'file:./config/' => app.description: "外部config目录application.yaml"
==============================================
最终生效的app.description值: 命令行参数
==============================================

提示：
使用 --spring.config.location 会覆盖默认搜索路径；
若想追加额外路径，应使用 --spring.config.additional-location。

结论：

1. -Dapp.description="JVM系统属性"和--app.description="命令行参数"都是属性值参数
2. --spring.config.location=file:./config/和--spring.profiles.active=prod是配置控制参数
3. --spring.profiles.active=prod会触发加载application-prod.yml配置文件
4. 虽然application-prod.yml被成功加载，但命令行参数--app.description="命令行参数"仍然具有最高优先级

实验五：外部配置目录优先级验证

java -Dfile.encoding=UTF-8 -jar demo-1.0-SNAPSHOT.jar --spring.config.location=file:./config/

输出结果：

==============================================
Spring Boot配置文件加载顺序与优先级演示
==============================================
配置属性源列表（按加载顺序显示）:
 1. Config resource 'file [config\application.yaml]' via location 'file:./config/' => app.description: "外部config目录application.yaml"
 2. Config resource 'file [config\application.yml]' via location 'file:./config/' => app.description: "外部config目录application.yml"
 3. Config resource 'file [config\application.properties]' via location 'file:./config/' => app.description: "外部config目录application.properties"
 4. random                                             => app.description: null
 5. systemEnvironment                                  => app.description: null
 6. systemProperties                                   => app.description: null
 7. servletContextInitParams                           => app.description: null
 8. servletConfigInitParams                            => app.description: null
 9. commandLineArgs                                    => app.description: null
==============================================
配置属性源列表（按优先级从高到低）:
 1. commandLineArgs                                    => app.description: null
 2. servletConfigInitParams                            => app.description: null
 3. servletContextInitParams                           => app.description: null
 4. systemProperties                                   => app.description: null
 5. systemEnvironment                                  => app.description: null
 6. random                                             => app.description: null
 7. Config resource 'file [config\application.properties]' via location 'file:./config/' => app.description: "外部config目录application.properties"
 8. Config resource 'file [config\application.yml]' via location 'file:./config/' => app.description: "外部config目录application.yml"
 9. Config resource 'file [config\application.yaml]' via location 'file:./config/' => app.description: "外部config目录application.yaml"
==============================================
最终生效的app.description值: 外部config目录application.properties
==============================================

结论：

1. 使用--spring.config.location可以指定自定义配置文件位置
2. 自定义位置的配置文件优先级高于默认位置
3. 同一目录下不同格式的配置文件加载顺序为：.properties > .yml > .yaml

四、配置加载机制深入解析

文件加载顺序与覆盖机制

在Spring Boot中，配置文件的加载遵循"后加载覆盖先加载"的原则。这意味着：

1. 同一属性在多个配置文件中定义时，后加载的文件中的值会覆盖先加载的文件中的值
2. 加载顺序按照优先级从低到高进行，优先级高的位置的文件会后加载

例如，在默认配置下：

1. 首先加载classpath:/application.yaml (优先级较低)
2. 然后加载classpath:/application.yml
3. 接着加载classpath:/application.properties
4. 然后加载classpath:/config/application.yaml
5. 依此类推，最后加载file:./config/application.properties (优先级最高)

如果app.description在所有这些文件中都有定义，最终生效的将是file:./config/application.properties中的值。

为什么--spring.profiles.active=prod能触发application-prod.yaml加载？

--spring.profiles.active=prod是一个配置控制参数，它在Spring Boot的配置加载阶段起作用：

1. 在Spring Boot启动过程中，会先解析命令行参数
2. 发现--spring.profiles.active=prod参数后，会将prod作为激活的profile
3. 在配置文件加载阶段，会根据激活的profile，按照优先级顺序加载对应的profile-specific配置文件
4. 这个过程发生在属性解析之前，所以即使--参数在命令行中排在最后，它仍然能影响配置文件的加载过程

这解释了为什么配置控制参数能够影响配置文件的加载顺序，而不仅仅是属性值的优先级。

五、实践应用总结

场景	推荐做法
多环境配置	使用 --spring.profiles.active 切换
容器部署	通过 --spring.config.location 或挂载 /config
敏感配置	使用环境变量或命令行参数注入

六、核心原则总结

1. 命令行参数最高优先级
2. ⚠️ 外部配置优于内部配置
3. 特定环境配置覆盖通用配置
4. 同级目录下 config 优先
5. 后加载覆盖先加载
6. ⚠️ 加载与解析分离：控制与赋值两个阶段
7. 同一目录下配置文件格式优先级：.properties > .yml > .yaml

七、版本注意事项

Spring Boot 3.x 采用全新的 ConfigData 加载机制，
原则一致但底层实现差异较大，建议阅读对应版本文档。

参考文档

1. Spring Boot官方文档 - Externalized Configuration
2. Spring Boot Properties and Configuration
3. Spring Framework - PropertySource