How to resolve Spring Boot web application error "Whitelabel Error Page This application has no explicit mapping for /error, so you are seeing this as a fallback."

If you come across  any such error as like below

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
.........
There was an unexpected error (type=Not Found, status=404).
No message available

then one possible problem would be that the below class wouldn't had been created

For HTML pages use the below class

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

@Configuration
@EnableWebMvc
public class ApplicationWebMvcConfig extends WebMvcConfigurerAdapter{

    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }
   
    @Bean
    public InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/html/");
        resolver.setSuffix(".html");
        return resolver;
    }
}

For JSP pages use the below class

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;

import org.springframework.web.servlet.config.annotation.EnableWebMvc;

import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

import org.springframework.web.servlet.view.InternalResourceViewResolver;

@Configuration

@EnableWebMvc

public class ApplicationWebMvcConfig extends WebMvcConfigurerAdapter{

    @Override

    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {

        configurer.enable();

    }

    

    @Bean

    public InternalResourceViewResolver viewResolver() {

        InternalResourceViewResolver resolver = new InternalResourceViewResolver();

        resolver.setPrefix("/WEB-INF/jsp/");

        resolver.setSuffix(".jsp");

        return resolver;

    }

}