How to declare ExceptionHandlerExceptionResolver in java code?

Question

I was reading this article Exception Handling in Spring MVC, and I don't understand why class extending ExceptionHandlerExceptionResolver doesn't have any annotations to it.

It should be a bean, right? So it must be annotated with @Component (or maybe @Service, but I'm not sure if it belongs to a service layer) annotation or something?

So why it does not have any annotations and how then Spring knows that it's a bean and that it should be used?

Answer 1

You have to manually add your handler to the list of handlers (in the example below I use a SImpleMappingExceptionsResolver, but you can use your own implementation):

package eu.anastasis.readingtrainer.configuration;
import java.util.List;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.handler.SimpleMappingExceptionResolver;

@Configuration
@EnableWebMvc
public class ConfigurationAdapter extends WebMvcConfigurerAdapter {

    @Override
    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
        exceptionResolvers.add(new SimpleMappingExceptionResolver());
    }

}

Please note that in this way you override any @ControllerAdvice + @ExceptionHandler you may have set (I don't know how to combine both strategies).

Answer 2

Just as an update to @Andrea Pegoretti answer, in Spring 5.X.X WebMvcConfigurerAdapter is deprecated, instead use WebMvcConfigurer interface; please refer to this link for more details.