05【掌握】springboot启动分析【难点】

@SpringBootApplication

@Target(ElementType.***TYPE***)

@Retention(RetentionPolicy.***RUNTIME***)

@Documented

@Inherited

@SpringBootConfiguration 就是对spring里面的@Configruation的包装

@EnableAutoConfiguration 启动自动配置

//扫描

@ComponentScan(excludeFilters = { @Filter(type = FilterType.***CUSTOM***, classes = TypeExcludeFilter.**class**),

  @Filter(type = FilterType.***CUSTOM***, classes = AutoConfigurationExcludeFilter.**class**) })

@ConfigurationPropertiesScan

**public**  **@interface**  SpringBootApplication {

@EnableAutConfigruation

@Target(ElementType.***TYPE***)

@Retention(RetentionPolicy.***RUNTIME***)

@Documented

@Inherited

@AutoConfigurationPackage //自动配置的包

@Import(AutoConfigurationImportSelector.**class**) //导入自己配置配置的配置类

**public**  **@interface**  EnableAutoConfiguration {

@AutoConfigurationPackage

@Target(ElementType.***TYPE***)

@Retention(RetentionPolicy.***RUNTIME***)

@Documented

@Inherited

@Import(AutoConfigurationPackages.Registrar.**class**) //自己扫描包的配置类

**public**  **@interface**  AutoConfigurationPackage {

}

进入AutoConfigurationPackages.Registrar.class

image.png

进入register方法

image.png

可以看出默认扫描的就是当前启动类所在的包

如何加载自动配置类

回到EnableAutoConfiguration

image.png

进入AutoConfigurationImportSelector

<servlet>

 <servlet-name>springmvc</servlet-name>

<servlet-class> org.springframework.web.servlet.DispatcherServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>springmvc</servlet-name>

<url-patten>/ </url-patten>

</servlet-mapping>

查看getAutoConfigurationEntry

image.png

发现springboot默认加载了124个自动配置类

image.png

下面的代码走完之后发现只有22个了。因为有些配置类不满足条件，被移除了

那124个自动配置类是如何加进来的

image.png image.png image.png image.png

springboot提供了哪些starter

https://docs.spring.io/spring-boot/docs/2.1.3.RELEASE/reference/htmlsingle/#using-boot-starter