[FIXED] MappedInterceptor Bean Vs WebMvcConfigurer addInterceptors. What is the correct (modern) way for adding Spring HandlerInterceptor?

Issue

I stumbled upon a configuration class for a project that was converted from legacy spring to Spring Boot. I see there are two ways interceptors are added. Like these

  @Configuration
  public class AppConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
     registry.addInterceptor( new MyInterceptorOne()).addPathPatterns("/api/data/**");
    }

    @Bean
    public MappedInterceptor mappedResponseHeaderInterceptor() {
        return new MappedInterceptor(new String[] { "/static/css/**", "/static/img/**" }, new ResponseHeaderInterceptor());
    }
  }
  

both interceptors are working. I am wondering what is right way to add the interceptors in Spring boot and why these two method exists

Solution

Basically they are the same.

registry.addInterceptor( new MyInterceptorOne()).addPathPatterns("/api/data/**");

Will internally use the MappedInterceptor to register the HandlerInterceptor with the given URL pattern.

Now the registration of a HandlerInterceptor (which MappedInterceptor implements) as an @Bean works because Spring Boot (not plain Spring!) detects HandlerInterceptor beans in the context and automatically registers them for you. This won't work in a regular Spring application.

So the way to use is to use the InterceptorRegistry as that is the documented way and the MappedInterceptor is more of an internal support class.

Answered By - M. Deinum