英文:
What is the purpose of org.springframework.boot.spring-boot POM?
问题
这个POM在Spring Boot org.springframework.boot.spring-boot中的目的是什么？
它包括了：
org.springframework.spring-core
org.springframework.spring-context
因此在类似于org.springframework.boot.spring-boot-starter-web的项目中，你会有：
org.springframework.spring-webmvc
org.springframework.boot.spring-boot-starter
org.springframework.boot.spring-boot-starter-json
org.springframework.boot.spring-boot-starter-tomcat
为什么不直接将org.springframework.boot.spring-boot-starter-web设计为：
org.springframework.spring-webmvc
org.springframework.spring-core
org.springframework.spring-context
org.springframework.boot.spring-boot-starter-json
org.springframework.boot.spring-boot-starter-tomcat
英文:
What is the purpose of this POM in Sprint Boot org.springframework.boot.spring-boot
It includes
org.springframework.spring-core
org.springframework.spring-context
So in something like org.springframework.boot.spring-boot-starter-web you have
org.springframework.spring-webmvc
org.springframework.boot.spring-boot-starter
org.springframework.boot.spring-boot-starter-json
org.springframework.boot.spring-boot-starter-tomcat
Why not just make org.springframework.boot.spring-boot-starter-web
org.springframework.spring-webmvc
org.springframework.spring-core
org.springframework.spring-context
org.springframework.boot.spring-boot-starter-json
org.springframework.boot.spring-boot-starter-tomcat
答案1
得分: 2
spring-boot-starter有以下依赖项：
- jakarta.annotation-api
- spring-core
- spring-boot
- spring-boot-autoconfigure
- spring-boot-starter-logging
如果将spring-boot-starter替换为spring-core和spring-context，那么您将错过在spring-boot和spring-boot-autoconfigure中定义的所有类和注解（spring-boot依赖于spring-core和spring-context，但它自己实现了一些重要的类，见下文）。
以spring-boot-starter-web为例，通常我们需要在application.yml中设置server.port，这个属性在spring-boot-autoconfigure项目的ServerProperties类中定义（这就是为什么我们需要在org.springframework.boot.spring-boot-starter-web中使用spring-boot-starter），还有其他常用的属性，如server.address、server.servlet.context-path和server.ssl.*等等。它们都在spring-boot-autoconfigure项目中定义。
为了自动配置在ServerProperties中定义的属性，创建了ServletWebServerFactoryAutoConfiguration类，将ServerProperties作为参数，并将其值应用于设置类似tomcat的软件。
现在看看ServerProperties既没有使用@Configuration也没有使用@Component进行注解，因此在进行组件扫描时不会实例化它，因此创建了EnableConfigurationProperties注解来确保ServerProperties的实例将被注入。这个注解在spring boot项目中定义，所以我们需要spring-boot依赖。它在这里被使用。
关于什么是spring boot starter以及它是如何工作的，这篇文章很有帮助：快速构建Spring Boot Starter的简易指南。
英文:
spring-boot-starter has following dependencies:
jakarta.annotation-api
spring-core
spring-boot
spring-boot-autoconfigure
spring-boot-starter-logging
if you replace spring-boot-starter with spring-core and spring-context, then you miss out all the classes and annotations that are defined in spring-boot and spring-boot-autoconfigure(spring-boot depends on spring-core and spring-context, but it has implemented some important classes itself, see below).
take spring-boot-starter-web as an example, usually we need to set server.port in our application.yml, this property is defined in ServerProperties class in spring-boot-autoconfigure project(that's why we need spring-boot-starter in org.springframework.boot.spring-boot-starter-web), there are other commonly used properties such as server.address, server.servlet.context-path, and server.ssl.* ....etc.They are all defined here in spring-boot-autoconfigure project.
in order to auto configure the properties defined in ServerProperties, class ServletWebServerFactoryAutoConfiguration is created to take ServerProperties as a parameter and apply it's values to set up software like tomcat
now see that ServerProperties is neither annotated with @Configuration nor @Component, so it wouldn't be instantiated when component-scan is happening, so this annotation EnableConfigurationProperties is created to make sure ServerProperties's instance will be injected. this annotation is defined in spring boot project, that's why we need spring-boot dependency. And it's used
here.
for what is a spring boot starter and how it works, here is a helpful article: Quick Guide to Building a Spring Boot Starter
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