springboot学习之——SpringApplication.run方法
springboot 版本3.1.5
第一步
/**
* Static helper that can be used to run a {@link SpringApplication} from the
* specified source using default settings.
* @param primarySource the primary source to load
* @param args the application arguments (usually passed from a Java main method)
* @return the running {@link ApplicationContext}
*/
public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) {
return run(new Class<?>[] { primarySource }, args);
}
注释说的啥屁话，这玩意返回一个可配置的应用上下文ConfigurableApplicationContext。看这种名字的类就知道不简单。
run()方法其实创建了一个新的SpringApplication。这个新的SpringApplication会被添加一些属性。
到这里就没了，实例化SpringApplication之后，返回的是更加具体的ConfigurableApplicationContext，也就是说，后面的工作交给了ConfigurableApplicationContext，所以要研究它了。
/**
* Create a new {@link SpringApplication} instance. The application context will load
* beans from the specified primary sources (see {@link SpringApplication class-level}
* documentation for details). The instance can be customized before calling
* {@link #run(String...)}.
* @param resourceLoader the resource loader to use
* @param primarySources the primary bean sources
* @see #run(Class, String[])
* @see #setSources(Set)
*/
@SuppressWarnings({ "unchecked", "rawtypes" })
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
this.resourceLoader = resourceLoader;//null
Assert.notNull(primarySources, "PrimarySources must not be null");
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));//这个资源类就是自己
this.webApplicationType = WebApplicationType.deduceFromClasspath();//推断使用什么类型的web应用。我们经常用WEBMVC_INDICATOR_CLASS
this.bootstrapRegistryInitializers = new ArrayList<>(
getSpringFactoriesInstances(BootstrapRegistryInitializer.class));//启动注册实例化
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));//监听器
this.mainApplicationClass = deduceMainApplicationClass();//主应用类（就是自己项目的启动类）
}
第二步
ConfigurableApplicationContext
/**
* SPI interface to be implemented by most if not all application contexts.
* Provides facilities to configure an application context in addition
* to the application context client methods in the
* {@link org.springframework.context.ApplicationContext} interface.
*
* <p>Configuration and lifecycle methods are encapsulated here to avoid
* making them obvious to ApplicationContext client code. The present
* methods should only be used by startup and shutdown code.
*
* @author Juergen Hoeller
* @author Chris Beams
* @author Sam Brannen
* @since 03.11.2003
*/
public interface ConfigurableApplicationContext extends ApplicationContext, Lifecycle, Closeable {
}
SPI接口（串行外设接口，芯片和外设通信用的），实现了大多数应用上下文的SPI接口。注释翻译了结果还是配置应用上下文。
前面的run()创建了它，程序运行实际是用它来执行的。然而它还是接口，还是要看谁实现了它。
实现它的类也很多。找到一个我们熟悉的看看。AnnotationConfigServletWebApplicationContext
/**
* Create a new {@link AnnotationConfigServletWebApplicationContext}, deriving bean
* definitions from the given annotated classes and automatically refreshing the
* context.
* @param annotatedClasses one or more annotated classes, e.g. {@code @Configuration}
* classes
*/
public AnnotationConfigServletWebApplicationContext(Class<?>... annotatedClasses //注册被注解的类) {
this();
register(annotatedClasses);
refresh();
}