说说springboot启动机制 ----- maven对依赖的管理，场景器，SpringBootApplication，EnableAutoConfiguration几个注解，加载了Tomcat，Mvc ...

说说springboot启动机制
https://ke.qq.com/webcourse/index.html#cid=333216&term_id=100395479&taid=2568313133929888&vid=5285890788262993749

 

通过@EnableAutoConfiguration 加载

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration --->
@ComponentScan(
    excludeFilters = {@Filter(
    type = FilterType.CUSTOM,
    classes = {TypeExcludeFilter.class}
), @Filter(
    type = FilterType.CUSTOM,
    classes = {AutoConfigurationExcludeFilter.class}
)}
)
public @interface SpringBootApplication {
    @AliasFor(

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import({EnableAutoConfigurationImportSelector.class}) //------>通过
public @interface EnableAutoConfiguration {
    String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";

    Class<?>[] exclude() default {};

    String[] excludeName() default {};
}

@Import 把一个类通过这种方式交给Spring容器管理
@Import({EnableAutoConfigurationImportSelector.class}) 点进去看这个类，再看它的父类

@Deprecated
public class EnableAutoConfigurationImportSelector extends AutoConfigurationImportSelector {

    protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
        List<String> configurations = SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());
        Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct.");
        return configurations;
    }

看出它回到这个包的路径下读取这个spring.factories配置文件：重点看这个三个

 org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration这个文件中，有启动Tomcat

老师的版本是2.0

本人这个org.springframework.boot.autoconfigure 的jar包是1.5.10... 启动tomcat如下代码

WebMvcAutoConfiguration.java 文件中：主要通过enablewebmvc注解 把springmvc加载进来

 

手写spirngboot ,启动验证