How to trigger a callback post fetching an entity in spring boot

Question

@Service

    @GetMapping
    public Foo findByFooId(@RequestParam(name = "fid") String fooId) {
        return fooService.findByFooId(fooId);
    }

I would like to trigger and save who viewed Foo, using a different method in FooService. Its like a PostConstruct callback for a successful response of findByFooId. How can this be achieved

Answer 1

One way is going to a custom HandlerInterceptor implementation.

• Definition of the interceptor

public class FooViewerInterceptor extends HandlerInterceptorAdapter {

    @Autowired
    FooService fooService;

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
    throws Exception {
       // if response succeeded ? http response code = 200 ?
       // extract the "who" logic
       // extract the fooId from request path
       fooService.viewedBy(fooId, userId); // example...
    }

}

• Register the interceptor. Note the path pattern specified with the custom interceptor instance.. just an example.

@Configuration  
public class AppConfig implements WebMvcConfigurer  {  

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
       registry.addInterceptor(new FooViewerInterceptor()).addPathPatterns("/foo/**");
    }
}