Spring Boot--01 Error Handling

package com.smartmap.sample.ch1.controller.view;

import java.io.IOException;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.web.ErrorProperties;
import org.springframework.boot.autoconfigure.web.servlet.error.AbstractErrorController;
import org.springframework.boot.autoconfigure.web.servlet.error.ErrorViewResolver;
import org.springframework.boot.web.servlet.error.DefaultErrorAttributes;
import org.springframework.boot.web.servlet.error.ErrorAttributes;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

import com.fasterxml.jackson.databind.ObjectMapper;

@Controller
public class ErrorViewController extends AbstractErrorController {
    final Log log = LogFactory.getLog(ErrorViewController.class);
    ErrorProperties errorProperties;

    @Autowired
    ObjectMapper objectMapper;

    public ErrorViewController() {
        super(new DefaultErrorAttributes());
    }

    public ErrorViewController(ErrorAttributes errorAttributes, ErrorProperties errorProperties,
            List<ErrorViewResolver> errorViewResolvers) {
        super(errorAttributes, errorViewResolvers);
        this.errorProperties = errorProperties;
    }

    @Override
    public String getErrorPath() {
        return errorProperties.getPath();
    }

    @RequestMapping("/error")
    public ModelAndView getErrorInfo(HttpServletRequest request, HttpServletResponse response) {

        Map<String, Object> model = Collections.unmodifiableMap(getErrorAttributes(request, false));

        Throwable cause = this.getCause(request);
        int status = (Integer) model.get("status");
        String message = (String) model.get("message");
        String errorMessage = getErrorMessage(cause);
        log.info(status + "," + message, cause);
        response.setStatus(status);
        if (!isJsonRequest(request)) {
            ModelAndView modelAndView = new ModelAndView();
            modelAndView.addAllObjects(model);
            modelAndView.addObject("errorMessage", errorMessage);
            modelAndView.addObject("status", status);
            modelAndView.addObject("cause", cause);
            return modelAndView;
        } else {
            Map<String, Object> error = new HashMap();
            error.put("errorMessage", errorMessage);
            error.put("status", status);
            error.put("cause", cause);

            writeJson(response, error);
            return null;

        }
    }

    protected Throwable getCause(HttpServletRequest request) {
        Throwable error = (Throwable) request.getAttribute("javax.servlet.error.exception");
        if (error != null) {
            while (error instanceof ServletException && error.getCause() != null) {
                error = ((ServletException) error).getCause();
            }
        }

        return error;

    }

    protected void writeJson(HttpServletResponse response, Map error) {
        response.setContentType("application/json;charset=utf-8");
        try {
            response.getWriter().write(objectMapper.writeValueAsString(error));
        } catch (IOException e) {
            // ignore
        }
    }

    protected String getErrorMessage(Throwable ex) {
         /* Do not display detailed errors to the front end */ 
        return "Server error, please contact the administrator" ;
    }

    protected boolean isJsonRequest(HttpServletRequest request) {
        return request.getHeader("Accept").contains("application/json");
    }

}