스프링 서블릿 오류 페이지 설정

스프링 빈 등록

package hello.exception;

import org.springframework.boot.web.server.ConfigurableWebServerFactory;
import org.springframework.boot.web.server.ErrorPage;
import org.springframework.boot.web.server.WebServerFactoryCustomizer;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Component;

@Component
public class WebServerCustomizer implements WebServerFactoryCustomizer<ConfigurableWebServerFactory> {

    @Override
    public void customize(ConfigurableWebServerFactory factory) {
        // 해당 에러 발생시 해당 컨트롤러 호출
        ErrorPage errorPage404 = new ErrorPage(HttpStatus.NOT_FOUND, "/error-page/404");
        ErrorPage errorPage500 = new ErrorPage(HttpStatus.INTERNAL_SERVER_ERROR, "/error-page/500");
        ErrorPage errorPageEx = new ErrorPage(RuntimeException.class, "/error-page/500");
        factory.addErrorPages(errorPage404, errorPage500, errorPageEx);
    }
}

에러 페이지 호출 컨트롤러

package hello.exception.servlet;

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;

import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Slf4j
@Controller
public class ServletExController {
    @GetMapping("/error-ex")
    public void errorEx(){
        throw new RuntimeException("예외 발생!!");
    }

    @GetMapping("/error-404")
    public void error404(HttpServletResponse response) throws IOException {
        response.sendError(404, "404 오류!!");
    }

    @GetMapping("/error-500")
    public void error500(HttpServletResponse response) throws IOException {
        response.sendError(500);
    }
}

에러 페이지 컨트롤러

package hello.exception.servlet;

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

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

@Controller
@Slf4j
public class ErrorPageController {

    //RequestDispatcher 상수로 정의되어 있음
    public static final String ERROR_EXCEPTION =
            "javax.servlet.error.exception";
    public static final String ERROR_EXCEPTION_TYPE =
            "javax.servlet.error.exception_type";
    public static final String ERROR_MESSAGE = "javax.servlet.error.message";
    public static final String ERROR_REQUEST_URI =
            "javax.servlet.error.request_uri";
    public static final String ERROR_SERVLET_NAME =
            "javax.servlet.error.servlet_name";
    public static final String ERROR_STATUS_CODE =
            "javax.servlet.error.status_code";

    @RequestMapping("/error-page/404")
    public String errorPage404(HttpServletRequest request, HttpServletResponse response) {
        log.info("errorPage 404");
        printErrorInfo(request);
        return "error-page/404";
    }

    @RequestMapping("/error-page/500")
    public String errorPage500(HttpServletRequest request, HttpServletResponse response) {
        log.info("errorPage 500");
        printErrorInfo(request);
        return "error-page/500";
    }

    // 어떤 예외인지 자세히 볼수 있는 함수
    private void printErrorInfo(HttpServletRequest request) {
        log.info("ERROR_EXCEPTION: ex=", request.getAttribute(ERROR_EXCEPTION));
        log.info("ERROR_EXCEPTION_TYPE: {}", request.getAttribute(ERROR_EXCEPTION_TYPE));
        log.info("ERROR_MESSAGE: {}", request.getAttribute(ERROR_MESSAGE)); //ex의 경우 NestedServletException 스프링이 한번 감싸서 반환
        log.info("ERROR_REQUEST_URI: {}", request.getAttribute(ERROR_REQUEST_URI));
        log.info("ERROR_SERVLET_NAME: {}", request.getAttribute(ERROR_SERVLET_NAME));
        log.info("ERROR_STATUS_CODE: {}", request.getAttribute(ERROR_STATUS_CODE));
        log.info("dispatchType={}", request.getDispatcherType());
    }
}