JWT

// 3. 토큰 만료예외가 발생하면 refershAuthentication(액세스 토큰 재발급)을 수행합니다.
private void authenticate(String accessToken, HttpServletRequest request, HttpServletResponse response) {
		try {
			Jwt.Claims claims = verify(accessToken);
			JwtAuthenticationToken authentication = createAuthenticationToken(claims, request, accessToken);
			SecurityContextHolder.getContext().setAuthentication(authentication);
		} catch (TokenExpiredException exception) {
			log.warn(exception.getMessage());
			refreshAuthentication(accessToken, request, response);
		} catch (JWTVerificationException exception) {
			log.warn(exception.getMessage());
		}
	}

private void refreshAuthentication(String accessToken, HttpServletRequest request, HttpServletResponse response) {
		try {
			String refreshToken = getRefreshToken(request);
			verifyRefreshToken(accessToken, refreshToken);
			String reIssuedAccessToken = accessTokenReIssue(accessToken);
			Jwt.Claims reIssuedClaims = verify(reIssuedAccessToken);
			JwtAuthenticationToken authentication = createAuthenticationToken(reIssuedClaims, request,
				reIssuedAccessToken);
			SecurityContextHolder.getContext().setAuthentication(authentication);
			ResponseCookie cookie = ResponseCookie.from(jwt.accessTokenProperties().header(),
					reIssuedAccessToken)
				.path("/")
				.httpOnly(true)
				.sameSite(cookieConfigProperties.sameSite().attributeValue())
				.domain(cookieConfigProperties.domain())
				.secure(cookieConfigProperties.secure())
				.maxAge(jwt.refreshTokenProperties().expirySeconds())
				.build();
			response.addHeader(SET_COOKIE, cookie.toString());

		} catch (EntityNotFoundException | JwtTokenNotFoundException | JWTVerificationException e) {
			log.warn(e.getMessage());
		}
	}

// 4. 쿠키로부터 RefreshToken을 가져옵니다. 이때 RefreshToken이 없다면 예외를 발생하고 더 이상의 인증 절차를 진행하지 않습니다.
private String getRefreshToken(HttpServletRequest request) {
		if (request.getCookies() != null) {
			return Arrays.stream(request.getCookies())
				.filter(cookie -> cookie.getName().equals(jwt.refreshTokenProperties().header()))
				.findFirst()
				.map(Cookie::getValue)
				.orElseThrow(() -> new JwtRefreshTokenNotFoundException("RefreshToken is not found."));
		} else {
			throw new JwtRefreshTokenNotFoundException();
		}
	}


private void verifyRefreshToken(String accessToken, String refreshToken) {
// 5. RefreshToken를 가져왔다면 토큰을 검증합니다. 
//   a. RefreshToken이 만료되거나 위변조되진 않았는지 확인합니다.
		jwt.verify(refreshToken);
//   b. 만료된 액세스 토큰에 담겨있고 id와 로그인 시 DB(Redis)에 RefreshToken과 함께 저장했던 id가 같은지 확인합니다.
		Long userId = jwt.decode(accessToken).userId;
		TokenResponse token = tokenService.findByUserId(userId);

		if (!userId.equals(token.userId())) {
			throw new JWTVerificationException("Invalid refresh token.");
		}
	}

// 6. 기존의 만료된 쿠키에 들어있던 Claim을 토대로 새로운 액세스 토큰을 재발급 받습니다.
private String accessTokenReIssue(String accessToken) {
		return jwt.generateAccessToken(jwt.decode(accessToken));
	}

private void refreshAuthentication(String accessToken, HttpServletRequest request, HttpServletResponse response) {
		try {
			String refreshToken = getRefreshToken(request);
			verifyRefreshToken(accessToken, refreshToken);
			String reIssuedAccessToken = accessTokenReIssue(accessToken);
			Jwt.Claims reIssuedClaims = verify(reIssuedAccessToken);
			JwtAuthenticationToken authentication = createAuthenticationToken(reIssuedClaims, request,
				reIssuedAccessToken);
// 7. 인증 객체를 생성하고 시큐리티 컨텍스트에 설정해줍니다.
			SecurityContextHolder.getContext().setAuthentication(authentication);
			ResponseCookie cookie = ResponseCookie.from(jwt.accessTokenProperties().header(),
					reIssuedAccessToken)
				.path("/")
				.httpOnly(true)
				.sameSite(cookieConfigProperties.sameSite().attributeValue())
				.domain(cookieConfigProperties.domain())
				.secure(cookieConfigProperties.secure())
				.maxAge(jwt.refreshTokenProperties().expirySeconds())
				.build();
// 8. 재발급 받은 액세스 토큰을 쿠키에 담아주고 응답합니다.
			response.addHeader(SET_COOKIE, cookie.toString());

		} catch (EntityNotFoundException | JwtTokenNotFoundException | JWTVerificationException e) {
			log.warn(e.getMessage());
		}
	}