参考视频 https://www.bilibili.com/video/BV19K4y1L7MT?p=7
spingboot其实自动配置了很多东西,参考spring-boot-starter-web-2.3.4RELEASE.pom:
<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<!-- This module was also published with a richer model, Gradle metadata, -->
<!-- which should be used instead. Do not delete the following line which -->
<!-- is to indicate to Gradle or any Gradle module metadata file consumer -->
<!-- that they should prefer consuming it instead. -->
<!-- do_not_remove: published-with-gradle-metadata -->
<modelVersion>4.0.0</modelVersion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
<version>2.3.4.RELEASE</version>
<name>spring-boot-starter-web</name>
<description>Starter for building web, including RESTful, applications using Spring MVC. Uses Tomcat as the default embedded container</description>
<url>https://spring.io/projects/spring-boot</url>
<organization>
<name>Pivotal Software, Inc.</name>
<url>https://spring.io</url>
</organization>
<licenses>
<license>
<name>Apache License, Version 2.0</name>
<url>https://www.apache.org/licenses/LICENSE-2.0</url>
</license>
</licenses>
<developers>
<developer>
<name>Pivotal</name>
<email>info@pivotal.io</email>
<organization>Pivotal Software, Inc.</organization>
<organizationUrl>https://www.spring.io</organizationUrl>
</developer>
</developers>
<scm>
<connection>scm:git:git://github.com/spring-projects/spring-boot.git</connection>
<developerConnection>scm:git:ssh://git@github.com/spring-projects/spring-boot.git</developerConnection>
<url>https://github.com/spring-projects/spring-boot</url>
</scm>
<issueManagement>
<system>GitHub</system>
<url>https://github.com/spring-projects/spring-boot/issues</url>
</issueManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<version>2.3.4.RELEASE</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-json</artifactId>
<version>2.3.4.RELEASE</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<version>2.3.4.RELEASE</version>
<scope>compile</scope>
</dependency>
<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>
</dependencies>
</project>
可以看到其自动配置了tomcat和mvc,同时它还会在启动时自动帮你加载一些常用的Bean,用来应付web常用的场景,比如DispatcherServlet,viewResovler, charcterEncodingFilter等等
与此同时,springboot拥有默认的包结构,就是启动类所在的包内,类加载的时候会自动扫描该包及其子包
如果想要该表扫描路径,就要使用@SpringBootApplication(scanBasePackage = 'com.atguigu')
同时各种配置拥有默认值, 比如在application.properties里的spring.servlet.multipart.max-file-size,而且配置值最终会绑定到每个类上(对应类MultipartProperties),这个类会在容器中创建对象
而且spingboot所有的自动配置都在spring-boot-autoconfigure里面,查找路径是从spring-boot-starter-web-> spring-boot-starter -> spring-boot-autoconfigure,可以看到,有很多的自动配置类