SpringBoot官方的场景 https://docs.spring.io/spring-boot/docs/current/reference/html/using-spring-boot.html#using-boot-starter 只要引入starter，这个场景的所有常规需要的依赖我们都自动引入

• 我们开发会导入starter场景启动器，见到很多spring-boot-starter-* 这是 springboot官方场景启动器。
• 另外，若见到 *-spring-boot-starter 这是第三方为我们提供的简化开发的场景启动器。

  以Springboot自带的Web开发场景为例

就是它<artifactId>spring-boot-starter-web</artifactId>，会自动帮我们配好5个功能

• spring-boot-starter
• spring-boot-starter-json
• spring-boot-starter-tomcat
• spring-web

• spring-webmvc ```java <?xml version=”1.0” encoding=”UTF-8”?> <project xmlns=”http://maven.apache.org/POM/4.0.0“

     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

  4.0.0

  com.atguigu boot-01-helloworld 1.0-SNAPSHOT

  jar

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.3.4.RELEASE</version>
</parent>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <optional>true</optional>
    </dependency>

</dependencies>
<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

点进`<artifactId>spring-boot-starter-web</artifactId>`发现，该Web场景启动器有5个依赖
```java
  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
      <version>2.4.0</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-json</artifactId>
      <version>2.4.0</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-tomcat</artifactId>
      <version>2.4.0</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>5.3.1</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.3.1</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

Web场景自动注入autoconfigure.jar/web

starter都与springboot的 spring-boot-autoconfigure相对应，即spring-boot-autoconfigure-2.3.4.RELEASE.jar，SpringBoot所有的自动配置功能都在spring-boot-autoconfigure-2.3.4.RELEASE.jar包里面,里面有springboot全场景

默认配置最终都是映射到某个类上，这个类由@ConfigurationProperties指定，如文件上传相关的：MultipartProperties，yaml/properties配置文件的值最终会绑定某个类上，这个类会在容器中创建对象。比如我们引入了web场景，则位于spring-boot-autoconfigure-2.3.4.RELEASE.jar包下的web配置都会生效了：
@ConfigurationProperties(prefix = "spring.servlet.multipart", ignoreUnknownFields = false)

autoconfigure.jar当中的类并不是全部生效
需要注意的是，引入了哪些场景这个场景的spring-boot-autoconfigure-2.3.4.RELEASE.jar自动配置才会开启，不引入场景则该场景对应的自动配置就不会生效：比如我们没有引入batch批处理场景

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.atguigu</groupId>
    <artifactId>boot-01-helloworld</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
    </parent>
<!--    <properties>-->
<!--        <mysql.version>5.1.43</mysql.version>-->
<!--    </properties>-->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>
<!--        <dependency>-->
<!--            <groupId>org.springframework.boot</groupId>-->
<!--            <artifactId>spring-boot-starter-batch</artifactId>-->
<!--        </dependency>-->
<!--        <dependency>-->
<!--            <groupId>mysql</groupId>-->
<!--            <artifactId>mysql-connector-java</artifactId>-->
<!--        </dependency>-->
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>