【Java 开发日记】我们来说一说 Redis 主从复制的原理及作用

当然了解，Spring Boot 的参数配置是其核心特性之一，也是它实现“约定大于配置”理念的关键。它极大地简化了传统 Spring 应用中繁琐的 XML 配置。

一、核心概念：application.properties 与 application.yml
Spring Boot 默认使用这两种文件进行配置（二者选其一即可，.yml 更常用）。

运行项目并下载源码
application.yml (YAML 格式，层次感更强，推荐使用)

logging:
level:
com.example.demo: debug
运行项目并下载源码

YAML 注意事项：缩进必须使用空格，不能使用 Tab 键，冒号后面必须有一个空格。

二、配置的加载位置与优先级
Spring Boot 会从以下位置按从高到低的优先级加载 application 配置文件（高优先级的配置会覆盖低优先级的配置）：

当前项目根目录下的 /config 子目录
当前项目根目录
classpath 下的 /config 包 (即 src/main/resources/config)
classpath 根路径 (即 src/main/resources)
最佳实践：在开发时，将通用配置放在 src/main/resources/application.yml 中。在打包部署时，可以在 JAR 包所在目录创建一个 config 文件夹，里面放一个 application.yml 来覆盖开发环境的配置（如数据库连接），这样就实现了配置与代码分离。

三、外部化配置（非常强大）
除了配置文件，Spring Boot 还支持多种外部配置方式，优先级高于 application.yml。这在容器化部署（如 Docker）时尤其有用。

命令行参数
java -jar yourapp.jar --server.port=8888 --spring.datasource.url=jdbc:mysql://prod-server:3306/proddb
运行项目并下载源码
操作系统环境变量
Spring Boot 会自动识别形如 SPRING_DATASOURCE_URL 的环境变量（注意大小写和下划线）。

Profile-specific 配置（多环境配置）

这是管理不同环境（开发、测试、生产）配置的最佳方式。

约定大于配置：提供了大量默认配置，开箱即用。
配置外部化：允许你通过文件、命令行、环境变量等多种方式覆盖默认配置，轻松适应不同环境。
类型安全绑定：通过 @ConfigurationProperties 可以轻松地将一组配置映射到 Java Bean 上，是管理自定义配置的首选方式。
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