67.原理解析-SpringApplication创建初始化流程

springboot的创建初始化流程

• 传递主程序类
  

创建spring应用

this.resourceLoader = resourceLoader; 
//资源加载器
Assert.notNull(primarySources, "PrimarySources must not be null");
//断言，如果没有主程序类则打印"xxx" 
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
//保存主配置类信息
this.webApplicationType = WebApplicationType.deduceFromClasspath();
//决定当前web应用的类型 利用Class.utils
this.bootstrapRegistryInitializers = new ArrayList<>();
//初始启动器  List<BootstrapRegistryInitializer> 

进入WebApplicationType.deduceFromClasspath()

• 首先判断是否为响应式编程
• 判断为原生servlet编程

== 判断完毕，继续执行 ==

    this.bootstrapRegistryInitializers = new ArrayList<>(
getSpringFactoriesInstances(BootstrapRegistryInitializer.class));
    //去spring.factories文件中找org.springframework.boot.Bootstrapper
    //bootstrappers:初始化启动引导器
    setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
    //去spring.factories文件中找ApplicationContextInitializer
    setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    //去spring.factories文件中找应用监听器ApplicationListener
    this.mainApplicationClass = deduceMainApplicationClass();

getSpringFactoriesInstances方法就是去spring.factories文件中找相应的配置文件

    private <T> Collection<T> getSpringFactoriesInstances(Class<T> type) {
        return getSpringFactoriesInstances(type, new Class<?>[] {});
    }

    private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
        ClassLoader classLoader = getClassLoader();
        //类加载器
        // Use names and ensure unique to protect against duplicates
        Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
        List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
        AnnotationAwareOrderComparator.sort(instances);
        return instances;
    }

七个初始化器

• 
• 将初始化器，监听器，引导器保存完毕就设定主程序
  
• for循环的意义在于：在栈中找有main方法的类

至此，springApplication初始化创建完毕