Spring Boot 2 - controller to handle error and display custom response (404 status, etc.)

In this short article, we would like to show how to add custom controller that handles error requests logging them to console under Spring Boot 2.

Example preview:

Note: the below solution was tested under Spring Boot 2.6.1.

Add following files to your project:

application.properties file:

...

server.error.path=/error

...

CustomErrorController.java file:

package com.example.controllers;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.boot.web.servlet.error.ErrorController;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;

@Controller
public class CustomErrorController implements ErrorController {

    private static final Logger log = LogManager.getLogger(CustomErrorController.class);

    @RequestMapping(value = "${server.error.path}")
    @ResponseBody
    public String getError(HttpServletRequest request) {

        String servletUri = (String) request.getAttribute("javax.servlet.error.request_uri");
        Integer servletStatus = (Integer) request.getAttribute("javax.servlet.error.status_code");
        String servletMessage = (String) request.getAttribute("javax.servlet.error.message");
        Throwable servletException = (Throwable) request.getAttribute("javax.servlet.error.exception");

        if (servletException == null) {
            log.warn("[ERROR]: " + servletStatus + " " + servletUri + " " + servletMessage);
        } else {
            String exceptionMessage = servletException.getMessage();
            log.warn("[ERROR]: " + servletStatus + " " + servletUri + " " + servletMessage + "\n" + exceptionMessage);
        }

        return "Error detected!";  // <--- change it to your custom response
    }
}

Example log:

2021-12-21 02:18:55.793  WARN 3352 --- [0.0-443-exec-10] c.e.c.CustomErrorController  : [ERROR]: 404 /style.css
2021-12-21 02:18:55.793  WARN 3352 --- [.0.0-443-exec-9] c.e.c.CustomErrorController  : [ERROR]: 404 /script.js
2021-12-21 02:18:56.585  WARN 3352 --- [.0.0-443-exec-7] c.e.c.CustomErrorController  : [ERROR]: 404 /logo.png