org.springframework.boot.WebApplicationType#SERVLET源码实例Demo

@Override
public void initialize()
        throws ContainerInitializationException {
    Timer.start("SPRINGBOOT2_COLD_START");

    SpringApplicationBuilder builder = new SpringApplicationBuilder(getEmbeddedContainerClasses())
            .web(springWebApplicationType); // .REACTIVE, .SERVLET
    if (springProfiles != null) {
        builder.profiles(springProfiles);
    }
    applicationContext = builder.run();
    if (springWebApplicationType == WebApplicationType.SERVLET) {
        ((AnnotationConfigServletWebServerApplicationContext)applicationContext).setServletContext(getServletContext());
        AwsServletRegistration reg = (AwsServletRegistration)getServletContext().getServletRegistration(DISPATCHER_SERVLET_REGISTRATION_NAME);
        if (reg != null) {
            reg.setLoadOnStartup(1);
        }
    }
    super.initialize();
    initialized = true;
    Timer.stop("SPRINGBOOT2_COLD_START");
}
 

private Class<?>[] getEmbeddedContainerClasses() {
    Class<?>[] classes = new Class[2];
    if (springWebApplicationType == WebApplicationType.REACTIVE) {
        try {
            // if HandlerAdapter is available we assume they are using WebFlux. Otherwise plain servlet.
            this.getClass().getClassLoader().loadClass("org.springframework.web.reactive.HandlerAdapter");
            log.debug("Found WebFlux HandlerAdapter on classpath, using reactive server factory");
            classes[0] = ServerlessReactiveServletEmbeddedServerFactory.class;
        } catch (ClassNotFoundException e) {
            springWebApplicationType = WebApplicationType.SERVLET;
            classes[0] = ServerlessServletEmbeddedServerFactory.class;
        }
    } else {
        classes[0] = ServerlessServletEmbeddedServerFactory.class;
    }

    classes[1] = springBootInitializer;
    return classes;
}
 

@Override
public void onApplicationEvent(ApplicationEvent event) {
	if (event instanceof ApplicationContextInitializedEvent) {
		ApplicationContextInitializedEvent initialized = (ApplicationContextInitializedEvent) event;
		ConfigurableApplicationContext context = initialized.getApplicationContext();
		if (!(context instanceof GenericApplicationContext)) {
			throw new IllegalStateException("ApplicationContext must be a GenericApplicationContext");
		}
		if (!isEnabled(context.getEnvironment())) {
			return;
		}
		GenericApplicationContext generic = (GenericApplicationContext) context;
		ConditionService conditions = initialize(generic);
		functional(generic, conditions);
		apply(generic, initialized.getSpringApplication(), conditions);
	}
	else if (event instanceof ApplicationEnvironmentPreparedEvent) {
		ApplicationEnvironmentPreparedEvent prepared = (ApplicationEnvironmentPreparedEvent) event;
		if (!isEnabled(prepared.getEnvironment())) {
			return;
		}
		logger.info("Preparing application context");
		SpringApplication application = prepared.getSpringApplication();
		findInitializers(application);
		WebApplicationType type = getWebApplicationType(application, prepared.getEnvironment());
		Class<?> contextType = getApplicationContextType(application);
		if (type == WebApplicationType.NONE) {
			if (contextType == AnnotationConfigApplicationContext.class || contextType == null) {
				application.setApplicationContextClass(GenericApplicationContext.class);
			}
		}
		else if (type == WebApplicationType.REACTIVE) {
			if (contextType == AnnotationConfigReactiveWebApplicationContext.class || contextType == null) {
				application.setApplicationContextClass(ReactiveWebServerApplicationContext.class);
			}
		}
		else if (type == WebApplicationType.SERVLET) {
			if (contextType == AnnotationConfigServletWebServerApplicationContext.class || contextType == null) {
				application.setApplicationContextClass(ServletWebServerApplicationContext.class);
			}
		}
	}
}
 

public SpringBootProxyHandlerBuilder<RequestType> servletApplication() {
    this.applicationType = WebApplicationType.SERVLET;
    return self();
}