SpringBootApplication注解原理及代码详解

@SpringBootApplication
public class TomcatdebugApplication {

  public static void main(String[] args) {
    SpringApplication.run(TomcatdebugApplication.class, args);
  }

}

@SpringBootConfiguration
public class Config {
  @Bean
  public Map createMap(){
    Map map = new HashMap();
    map.put("username","gxz");
    map.put("age",27);
    return map;
  }
}

public static void main( String[] args )
  {
    //方式1 获取context
    ConfigurableApplicationContext cOntext= SpringApplication.run(App.class, args);
    context.getBean(Runnable.class).run();
    context.getBean("createMap");  //注意这里直接获取到这个方法bean
    int age = (int) map.get("age");
    System.out.println("age=="+age);
//方式2. 使用@Autowired注解，应用bean 
// @Autowired// Map createMap
}

public String[] selectImports(AnnotationMetadata annotationMetadata) {
 　　 //1.是否开启自动配置，默认开启
  if (!this.isEnabled(annotationMetadata)) {
    return NO_IMPORTS;
  } else {
    try {
 　　　　　　 //2.从META-INF/spring-autoconfigure-metadata.properties文件中载入属性配置（有一些有默认值），获取注解信息

      AutoConfigurationMetadata autoCOnfigurationMetadata= AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);
　　　　　　　
　　　　　　　//3.获取所有的配置列表
      AnnotationAttributes attributes = this.getAttributes(annotationMetadata);
      List cOnfigurations= this.getCandidateConfigurations(annotationMetadata, attributes);
      cOnfigurations= this.removeDuplicates(configurations);
      cOnfigurations= this.sort(configurations, autoConfigurationMetadata);
      Set exclusiOns= this.getExclusions(annotationMetadata, attributes);
      this.checkExcludedClasses(configurations, exclusions);
      configurations.removeAll(exclusions);
      cOnfigurations= this.filter(configurations, autoConfigurationMetadata);
      this.fireAutoConfigurationImportEvents(configurations, exclusions);
      return (String[])configurations.toArray(new String[configurations.size()]);
    } catch (IOException var6) {
      throw new IllegalStateException(var6);
    }
  }
}

 protected boolean isEnabled(AnnotationMetadata metadata) {
    return true;
  }

protected static final String PATH = "META-INF/spring-autoconfigure-metadata.properties";

  private AutoConfigurationMetadataLoader() {
  }

  public static AutoConfigurationMetadata loadMetadata(ClassLoader classLoader) {
    return loadMetadata(classLoader, "META-INF/spring-autoconfigure-metadata.properties");
  }
  static AutoConfigurationMetadata loadMetadata(ClassLoader classLoader, String path) {
    try {
      Enumeration urls = classLoader != null &＃63; classLoader.getResources(path) : ClassLoader.getSystemResources(path);
      Properties properties = new Properties();
      while(urls.hasMoreElements()) {
        properties.putAll(PropertiesLoaderUtils.loadProperties(new UrlResource((URL)urls.nextElement())));
      }
      return loadMetadata(properties);
    } catch (IOException var4) {
      throw new IllegalArgumentException("Unable to load @ConditionalOnClass location [" + path + "]", var4);
    }
  }

protected AnnotationAttributes getAttributes(AnnotationMetadata metadata) {
    String name = this.getAnnotationClass().getName();
    AnnotationAttributes attributes = AnnotationAttributes.fromMap(metadata.getAnnotationAttributes(name, true));
    Assert.notNull(attributes, "No auto-configuration attributes found. Is " + metadata.getClassName() + " annotated with " + ClassUtils.getShortName(name) + "&＃63;");
    return attributes;
  }