基于这个问题，我已经尝试了s中提到的所有解决方案。。。然而，没有一个能让人满意。。。
首先，这是我的java配置
webappinitializer.java

public class WebAppInitializer implements WebApplicationInitializer {

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        AnnotationConfigWebApplicationContext servletAppContext = new AnnotationConfigWebApplicationContext();
        servletAppContext.setConfigLocation("com.//////my project/////////.config");

        DispatcherServlet dispatcherServlet = new DispatcherServlet(servletAppContext);
        ServletRegistration.Dynamic dispatcher = servletContext.addServlet("dispatcher", dispatcherServlet);

        dispatcher.setLoadOnStartup(1);
        dispatcher.addMapping("/");
        enableThrowExceptionIfNoHandlerFound(dispatcher);

        AnnotationConfigWebApplicationContext rootContext = new AnnotationConfigWebApplicationContext();
        rootContext.register(RootConfig.class);
        servletContext.addListener(new ContextLoaderListener(rootContext));

        FilterRegistration.Dynamic filter = servletContext.addFilter("CHARACTER_ENCODING_FILTER", CharacterEncodingFilter.class);
        filter.setInitParameter("encoding", "UTF-8");
        filter.setInitParameter("forceEncoding", "true");
        filter.addMappingForUrlPatterns(null, false, "/*");

    }

    private void enableThrowExceptionIfNoHandlerFound(ServletRegistration.Dynamic registration) {
        registration.setInitParameter("throwExceptionIfNoHandlerFound", "true");
    }
}

根配置.java

@Configuration
@EnableWebMvc
public class RootConfig {
Environment env;

    @Autowired
    public void setEnv(Environment env) {
        this.env = env;
    }
}

servletconfig.java文件

@Configuration
@ComponentScan("com.////myproject//")
public class ServletConfig extends WebMvcConfigurerAdapter{

@Bean
public FreeMarkerViewResolver freemarkerViewResolver() {
    FreeMarkerViewResolver resolver = new FreeMarkerViewResolver();
    resolver.setContentType("text/html; charset=utf-8");
    resolver.setCache(true);
    resolver.setSuffix(".ftl");
    resolver.setExposeSpringMacroHelpers(true);
    return resolver;
}

@Bean
public FreeMarkerConfigurer freemarkerConfig(WebApplicationContext applicationContext) {

    freemarker.template.Configuration config = new freemarker.template.Configuration(freemarker.template.Configuration.VERSION_2_3_28);
    config.setDefaultEncoding("UTF-8");
    config.setTemplateExceptionHandler(TemplateExceptionHandler.DEBUG_HANDLER);
    config.setNumberFormat("#.######");
    config.setServletContextForTemplateLoading(applicationContext.getServletContext(), "/WEB-INF/views");

    config.setDateFormat("yyyy-MM-dd");
    config.setTimeFormat("hh:mm:ss");
    config.setDateTimeFormat("yyyy-MM-dd hh:mm:ss");
    FreeMarkerConfigurer freeMarkerConfigurer = new FreeMarkerConfigurer();
    freeMarkerConfigurer.setConfiguration(config);
    return freeMarkerConfigurer;
}

@Override
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {

}

@Override
public void addResourceHandlers(final ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/**").addResourceLocations("/assets/");
}
}

errorcontrolleradvice.java错误控制器

@ControllerAdvice
public class ErrorControllerAdvice {

    @ResponseStatus(HttpStatus.NOT_FOUND)
    @ExceptionHandler(NoHandlerFoundException.class)
    public ModelAndView NotFoundPage() {
        log.info("No Handler Found Exception");
        return new ModelAndView("/error/404");
    }

    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
    @ExceptionHandler(NullPointerException.class)
    public ModelAndView NPEPage() {
        log.info("NullPointerException");
        return new ModelAndView("/error/500");
    }

    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
    @ExceptionHandler(ClassNotFoundException.class)
    public ModelAndView ClassNotFoundPage() {
        log.info("ClassNotFound");
        return new ModelAndView("/error/500");
    }

    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
    @ExceptionHandler(InternalServerErrorException.class)
    public ModelAndView InternalServerErrorPage() {
        log.info("InternalServerError");
        return new ModelAndView("/error/500");
    }
}

在此配置中，某些与DispatcherServlet无关的异常，例如 NullPointerException , ClassNotFoundException 自定义错误页运行良好。。
但是，与DispatcherServlet相关的部分显示了tomcat紫色的默认错误页。。。
有趣的是在servletconfig.java中

@Override
public void addResourceHandlers(final ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/**").addResourceLocations("/assets/");
}
}

没有这个方法，自定义404错误页就可以工作！但是，如果没有这个方法，js、css资源文件将无法应用。。。。。
再次使用此方法

INFO org.springframework.web.servlet.handler.SimpleUrlHandlerMapping - Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]

这个日志很特别，js、css资源也很好地工作。但是，404错误页返回到tomcat基本错误页。。。
不知怎么的 SimpleUrlHandlerMapping 正在启用 DefaultExceptionHandler ... 我试过了 WebMvcConfigurationSupport 而不是 WebMvcConfigurerAdapter 修改特定bean，例如 SimpleUrlHandlerMapping ... 虽然我想知道是否有更好的解决办法。。。。。