WebApplicationType＃deduceFromClasspath

其实就是从类路径中找这几个类，找到了就说明是SERVLET，没找到时其他处理，一般导入web场景是找到的。

    static WebApplicationType deduceFromClasspath() {
    
        if (ClassUtils.isPresent("org.springframework.web.reactive.DispatcherHandler", (ClassLoader)null) && !ClassUtils.isPresent("org.springframework.web.servlet.DispatcherServlet", (ClassLoader)null) && !ClassUtils.isPresent("org.glassfish.jersey.servlet.ServletContainer", (ClassLoader)null)) {
    
            return REACTIVE;
        } else {
    
            String[] var0 = SERVLET_INDICATOR_CLASSES;
            int var1 = var0.length;

            for(int var2 = 0; var2 < var1; ++var2) {
    
                String className = var0[var2];
                if (!ClassUtils.isPresent(className, (ClassLoader)null)) {
    
                    return NONE;
                }
            }

            return SERVLET;
        }
    }