[Java Spring MVC] Introduction to interceptors

Interceptor jump in before controller. So request may not reach controller if Pre-process is not ok.

Demo:

package com.test.hplus.interceptors;

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Date;

public class LoggingInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
       //get all cookies
        //log session id:
        //log the request path

        String sessionId = null;

        if(null!=request.getCookies()){
            for(Cookie cookie: request.getCookies()){
                if("JSESSIONID".equals(cookie.getName())){
                    sessionId = cookie.getValue();
                }
            }
        }

        System.out.println("Incoming request data log: session: "+sessionId+
                " at "+ new Date()+" for "+request.getRequestURI());

        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("in post handle");
    }
}

Add inteceptor to conifg:

@Configuration
@ComponentScan(basePackages = "com.test.hplus")
public class ApplicationConfig extends WebMvcConfigurationSupport {
 

    ...   

    @Override
    protected void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoggingInterceptor()).addPathPatterns("/*");
    }
}

For each requests, login interceptor will jump in.

Forwarding request from login controller to profile controller:

    @PostMapping("/login")
    public String login(@ModelAttribute("login")Login login){
        User user  = userRepository.searchByName(login.getUsername());
        if(user==null){
            throw new ApplicationException("User not found");
        }
        return "forward:/userprofile";
    }

@Controller
public class UserProfileController {

    @PostMapping("/userprofile")
    public String getUserProfile(@SessionAttribute("login")Login login, Model model){
        System.out.println("in user profile controller");
        System.out.println("username from session: "+login.getUsername());
        //call to userrepository to get all the user information
        model.addAttribute("username", login.getUsername());
        return "profile";
    }
}