springboot学习之——SpringApplication.run方法

springboot学习之——SpringApplication.run方法

• springboot学习之——SpringApplication.run方法
  • 第一步
  • 第二步
    • ConfigurableApplicationContext

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();
	}