查看“Spring Boot 自动配置特性”的源代码

https://www.bilibili.com/video/BV19K4y1L7MT/?p=7

=== 怎么自动配好 Tomcat的？ ===

==== 怎么引入 tomcat 依赖的？ ====
boot-01-helloworld - pom.xml<syntaxhighlight lang="xml">
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

    </dependencies>
</syntaxhighlight>


spring-boot-starter-web-x.x.x.RELEASE.pom<syntaxhighlight lang="xml">
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-tomcat</artifactId>
      <version>2.3.4.RELEASE</version>
      <scope>compile</scope>
    </dependency>
</syntaxhighlight>



=== 自动配置好 Spring MVC ===
spring-boot-starter-web-x.x.x.RELEASE.pom<syntaxhighlight lang="xml">
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>5.2.9.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.2.9.RELEASE</version>
      <scope>compile</scope>
    </dependency>
</syntaxhighlight>



=== 思考：在 Spring Boot 出现之前，使用 Spring MVC 要有哪些配置？ ===
web.xml<syntaxhighlight lang="xml">
<!--配置DispatcherServlet -->
  <servlet>
    <servlet-name>spring-dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <!-- 配置SpringMVC需要加载的配置文件 spring-mvc.xml -->
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:spring-mvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>spring-dispatcher</servlet-name>
    <!--默认匹配所有的请求 -->
    <url-pattern>/</url-pattern>
  </servlet-mapping>
</syntaxhighlight>为什么在 Spring Boot 出现之后，不进行如上的配置也可以进行使用；如果这些配置已经在 Spring Boot 内部实现了，是怎么实现的？